A Study on Mechanical Properties of Aluminium Alloy (LM6) Reinforced with SiC...IOSR Journals
This work deals with fabricating or producing aluminium based metal matrix composite and then
studying its microstructure and mechanical properties such as tensile strength, impact strength and wear
behavior of produced test specimen. In the present study a modest attempt has been made to develop aluminium
based MMCs with reinforcing material, with an objective to develop a conventional low cast method of
producing MMCs and to obtain homogeneous dispersion of reinforced material. To achieve this objective stir
casting technique has been adopted. Aluminium Alloy (LM6) and SiC, Fly Ash has been chosen as matrix and
reinforcing material respectively. Experiment has been conducted by varying weight fraction of Fly Ash ( 5%
and 15%) while keeping SiC constant(5%). The result shown that the increase in addition of Fly Ash increases
the Tensile Strength, Impact Strength, Wear Resistance of the specimen and decreases the percentage of
Elongation
Editor: Eng. Mohamadreza Govahi
Mentor: Dr. Ehsan Borhani
Date of Presentation: Apr 2016, Semnan PN Univeristy
*Contents
~Introduction to MMCs
~Introduction to Aluminum MMCs (AMMCs)
~Ceramic Reinforcements in AMMCs
~Types and Morphology of Reinforcements
~Aluminum Nano-composites
~Producing Methods
~Comparison in Different Procedures
~Reviews of some Experiments And Researches
SiC and ZrO2 Weigh Percentage Effects on Microstructure of Al Based Matrix Co...INFOGAIN PUBLICATION
SiC and ZrO2 particle are succesfully reaction synthesized from powder of Al, ZrO2 and SiC using spark plasma sintering method. The XRD of sintered composite and microstructure of the aas-sintered products. With the ZrO2 content increasing, the grains are remarkably refined and the and the ZrO2 and nano SiC particles are dispersing more uniformly in Al matrix, forming a homogeneous structure with the least porosity.
Studies On Fracture Toughness Behavior of Hybrid Aluminum Metal Matrix Compos...IJERA Editor
The limited mechanical properties of Al and its alloys adversely affect its applications in automobile and
aerospace industries. This remains one of the major concern in the fabrication to suit its application in recent
days. The main aim of the present work is to improve the fracture toughness of the Al matrix composite . A
composite with Al 6061 alloy as matrix and Zirconium Oxide as reinforcement is fabricated by stir casting
process. The specimens were prepared according to ASTM standards and fracture toughness, tensile and
hardness tests were performed and the properties were investigated. Zirconium oxide is selected as a
reinforcement because of its ability to influence the microstructure of the Al 6061 alloy to improve the fracture
toughness. The fracture toughness is highest at 6% reinforcement of ZrO2 and hardness is found to be more at
4% reinforcement
A Study on Mechanical Properties of Aluminium Alloy (LM6) Reinforced with SiC...IOSR Journals
This work deals with fabricating or producing aluminium based metal matrix composite and then
studying its microstructure and mechanical properties such as tensile strength, impact strength and wear
behavior of produced test specimen. In the present study a modest attempt has been made to develop aluminium
based MMCs with reinforcing material, with an objective to develop a conventional low cast method of
producing MMCs and to obtain homogeneous dispersion of reinforced material. To achieve this objective stir
casting technique has been adopted. Aluminium Alloy (LM6) and SiC, Fly Ash has been chosen as matrix and
reinforcing material respectively. Experiment has been conducted by varying weight fraction of Fly Ash ( 5%
and 15%) while keeping SiC constant(5%). The result shown that the increase in addition of Fly Ash increases
the Tensile Strength, Impact Strength, Wear Resistance of the specimen and decreases the percentage of
Elongation
Editor: Eng. Mohamadreza Govahi
Mentor: Dr. Ehsan Borhani
Date of Presentation: Apr 2016, Semnan PN Univeristy
*Contents
~Introduction to MMCs
~Introduction to Aluminum MMCs (AMMCs)
~Ceramic Reinforcements in AMMCs
~Types and Morphology of Reinforcements
~Aluminum Nano-composites
~Producing Methods
~Comparison in Different Procedures
~Reviews of some Experiments And Researches
SiC and ZrO2 Weigh Percentage Effects on Microstructure of Al Based Matrix Co...INFOGAIN PUBLICATION
SiC and ZrO2 particle are succesfully reaction synthesized from powder of Al, ZrO2 and SiC using spark plasma sintering method. The XRD of sintered composite and microstructure of the aas-sintered products. With the ZrO2 content increasing, the grains are remarkably refined and the and the ZrO2 and nano SiC particles are dispersing more uniformly in Al matrix, forming a homogeneous structure with the least porosity.
Studies On Fracture Toughness Behavior of Hybrid Aluminum Metal Matrix Compos...IJERA Editor
The limited mechanical properties of Al and its alloys adversely affect its applications in automobile and
aerospace industries. This remains one of the major concern in the fabrication to suit its application in recent
days. The main aim of the present work is to improve the fracture toughness of the Al matrix composite . A
composite with Al 6061 alloy as matrix and Zirconium Oxide as reinforcement is fabricated by stir casting
process. The specimens were prepared according to ASTM standards and fracture toughness, tensile and
hardness tests were performed and the properties were investigated. Zirconium oxide is selected as a
reinforcement because of its ability to influence the microstructure of the Al 6061 alloy to improve the fracture
toughness. The fracture toughness is highest at 6% reinforcement of ZrO2 and hardness is found to be more at
4% reinforcement
Design and Fabrication of a Stir Casting Furnace Set-UpIJERA Editor
Now-a-days a large variety of heating techniques/furnaces are available. There may be many method for supplying heat to the work but heat is produced either by combustion of fuel or electric resistance heating. Taking into consideration the effect of cost, safety, simplicity and ease of construction we are going for an electrical resistance heating furnace with indirect heating provisions. The stir casting furnace has two main parts that enable to perform all its operations, they are: Furnace Elements and Control Panel. This paper shows the design and fabrication of stir-casting furnace and aluminium melted and casted to form.
Aluminium Matrix Composites (AMC’s) are widely used in aerospace, automotive,
structural and marine applications due to their high strength to weight ratio, corrosion
resistance. In AMC one of constituent is aluminium or its alloy which forms a network
called as matrix phase and other constituent is embedded in matrix made of harder material
generally ceramic or non metallic material called as reinforcement. Various processing
techniques are available for manufacturing of AMC’s. Stir casting is one of the economical
and extensively used methods to enhance attractive properties of AMC’s. This paper
presents an overview of stir casing process, process parameter and preparation of AMC
using aluminium alloy as matrix phase and alumina (Al2O3) as reinforcement by varying
their proportion.
Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
DEVELOPMENT AND TRIBOLOGICAL CHARACTERIZATION OF DUAL PARTICLE AND TRIPLE PAR...ijmech
The this work the study on hardness and wear behaviour of dual particle and triple particle size Alumina (Al2O3) reinforced aluminium alloy based metal matrix composite (Al2O3-Al MMC) was carried out. AlMMCs were prepared using 10 vol% Al2O3 reinforcement into aluminium metal matrix and developed using stir casting process. Stir casting is a most suitable process for the production of particulate MMC in which the reinforcement is introduced in to the molten matrix material with simultaneous stirring. The reinforcement in the range of particle size with Dual particle and Triple particle at 10% olume fraction with range from coarse to fine size were used (210µ, 180µ, 80µ & 10µ).The hardness of the composite was
determined by Vickers hardness tester and Brinell Hardness Tester. Tensile strength was determined by Universal Testing Machine (UTM). The wear rate was found by pin-on-disc type wear testing machine with steel disc of 60HRC hardness in dry sliding condition. Wear test was conducted on all the samples
at speeds of 300,600 and 900 rpm by varying the load (2kg, 4kg, 6kg & 8kg) at a constant sliding distance of 55mm. The wear track studies were carried out by optical microscope .The test results showed that Dual particle composite and triple particle composite exhibited better hardness compared to as cast AL- 7075. Strength of Triple particle reinforced MMC was found to be higher than that of dual particle reinforced composite material. The wear resistance properties of dual particle MMC was higher compared to triple particle reinforced MMC. The secondary process will further enhances the wear resistance of the composite and also that heat treatment will promote the wear resistance.
A Study on Mechanical Properties of Fly Ash and Alumina Reinforced Aluminium ...IOSR Journals
The results of an experimental investigation of the mechanical properties of fly ash and Alumina
reinforced aluminium alloy (LM25) composites samples, processed by stir casting route are reported in this
paper. Three sets of composites with constant weight fraction of fly ash (particle size of 3-100 μm) and
Al2O3(particle size of 150 μm) with different wt% were used. Composite samples have the reinforcement weight
fractions of constant 3% fly Ash and varying %wt of 5, 10 and 15% Al2O3 . The main mechanical properties
studied were the tensile strength,ductilityimpact strength & hardness. Unreinforced LM25 samples were also
tested for the same properties. It was found that the tensile strength & hardness of the aluminium alloy (Lm25)
composites increases with the increase in %wt of Al2O3 upto certain limit. in addition of more amount of
reinforcement the Tensile strength decrease due to poor wettability of the reinforced material with metal
aluminium matrix .And the charpy test shows decrease in impact load absorption with increase in %weight
reinforcement.The Microstructure study of the samples indicated near uniform distribution of the fly ash and
Al2O3 particles in the matrix. LM25 alloy is mainly used where good mechanical properties are required in
castings of a shape or dimensions requiring an alloy of excellent castability in order to achieve the desired
standard of soundness.The alloy is also used where resistance to corrosion is an important consideration
particularly where highstrength is also required.
A Study on Mechanical and Tribological Properties of Magnesium Alloy AZ31 Rei...ijsrd.com
This work deals with fabricating or producing magnesium based metal matrix composite and then studying its mechanical and tribological properties such as microstructure, tensile strength, impact strength and wear behavior of produced test specimen. In the present study a modest attempt has been made to develop magnesium based MMCs with reinforcing material, with an objective to develop a conventional low cast method of producing MMCs and to obtain homogeneous dispersion of reinforced material. To achieve this objective stir casting technique has been adopted. An Alloy similar to commercially available composition of AZ31 and SiC, Al2O3 has been chosen as matrix and reinforcing material respectively. Experiment has been conducted by varying weight fraction of 3% SiC and 1% Al2O3 & 1% SiC and 3% Al2O3 in matrix metal. The result shown that tensile strength, impact strength, wear resistance is good in matrix metal as compared to used weight compositions of SiC and Al2O3 in the composites.
Design and Fabrication of a Stir Casting Furnace Set-UpIJERA Editor
Now-a-days a large variety of heating techniques/furnaces are available. There may be many method for supplying heat to the work but heat is produced either by combustion of fuel or electric resistance heating. Taking into consideration the effect of cost, safety, simplicity and ease of construction we are going for an electrical resistance heating furnace with indirect heating provisions. The stir casting furnace has two main parts that enable to perform all its operations, they are: Furnace Elements and Control Panel. This paper shows the design and fabrication of stir-casting furnace and aluminium melted and casted to form.
Aluminium Matrix Composites (AMC’s) are widely used in aerospace, automotive,
structural and marine applications due to their high strength to weight ratio, corrosion
resistance. In AMC one of constituent is aluminium or its alloy which forms a network
called as matrix phase and other constituent is embedded in matrix made of harder material
generally ceramic or non metallic material called as reinforcement. Various processing
techniques are available for manufacturing of AMC’s. Stir casting is one of the economical
and extensively used methods to enhance attractive properties of AMC’s. This paper
presents an overview of stir casing process, process parameter and preparation of AMC
using aluminium alloy as matrix phase and alumina (Al2O3) as reinforcement by varying
their proportion.
Study on hardening mechanisms in aluminium alloysIJERA Editor
The Al-Zn-Mg alloys are most commonly used age-hardenable aluminium alloys. The hardening mechanism is
further enhanced in addition of Sc. Sc additions to aluminium alloys are more promising. Due to the
heterogeneous distribution of nano-sized Al3Sc precipitates hardening effect can be accelerated. Mainly,
highlight on hardening mechanism in Al-Zn-Mg alloys with Sc effect is to study. In addition, several
characterisations have been done to age-hardening measurements at elevated temperatures from 120oC to 180
oC. The ageing kinetics has also been calculated from Arrhenius equation. Furthermore, friction stir processing
(FSP) can be introduced to surface modification process and hardened the cast aluminium alloys. In this study,
hardening mechanism can be evaluated by Vicker’s hardness measurement and mechanical testing is present
task.
DEVELOPMENT AND TRIBOLOGICAL CHARACTERIZATION OF DUAL PARTICLE AND TRIPLE PAR...ijmech
The this work the study on hardness and wear behaviour of dual particle and triple particle size Alumina (Al2O3) reinforced aluminium alloy based metal matrix composite (Al2O3-Al MMC) was carried out. AlMMCs were prepared using 10 vol% Al2O3 reinforcement into aluminium metal matrix and developed using stir casting process. Stir casting is a most suitable process for the production of particulate MMC in which the reinforcement is introduced in to the molten matrix material with simultaneous stirring. The reinforcement in the range of particle size with Dual particle and Triple particle at 10% olume fraction with range from coarse to fine size were used (210µ, 180µ, 80µ & 10µ).The hardness of the composite was
determined by Vickers hardness tester and Brinell Hardness Tester. Tensile strength was determined by Universal Testing Machine (UTM). The wear rate was found by pin-on-disc type wear testing machine with steel disc of 60HRC hardness in dry sliding condition. Wear test was conducted on all the samples
at speeds of 300,600 and 900 rpm by varying the load (2kg, 4kg, 6kg & 8kg) at a constant sliding distance of 55mm. The wear track studies were carried out by optical microscope .The test results showed that Dual particle composite and triple particle composite exhibited better hardness compared to as cast AL- 7075. Strength of Triple particle reinforced MMC was found to be higher than that of dual particle reinforced composite material. The wear resistance properties of dual particle MMC was higher compared to triple particle reinforced MMC. The secondary process will further enhances the wear resistance of the composite and also that heat treatment will promote the wear resistance.
A Study on Mechanical Properties of Fly Ash and Alumina Reinforced Aluminium ...IOSR Journals
The results of an experimental investigation of the mechanical properties of fly ash and Alumina
reinforced aluminium alloy (LM25) composites samples, processed by stir casting route are reported in this
paper. Three sets of composites with constant weight fraction of fly ash (particle size of 3-100 μm) and
Al2O3(particle size of 150 μm) with different wt% were used. Composite samples have the reinforcement weight
fractions of constant 3% fly Ash and varying %wt of 5, 10 and 15% Al2O3 . The main mechanical properties
studied were the tensile strength,ductilityimpact strength & hardness. Unreinforced LM25 samples were also
tested for the same properties. It was found that the tensile strength & hardness of the aluminium alloy (Lm25)
composites increases with the increase in %wt of Al2O3 upto certain limit. in addition of more amount of
reinforcement the Tensile strength decrease due to poor wettability of the reinforced material with metal
aluminium matrix .And the charpy test shows decrease in impact load absorption with increase in %weight
reinforcement.The Microstructure study of the samples indicated near uniform distribution of the fly ash and
Al2O3 particles in the matrix. LM25 alloy is mainly used where good mechanical properties are required in
castings of a shape or dimensions requiring an alloy of excellent castability in order to achieve the desired
standard of soundness.The alloy is also used where resistance to corrosion is an important consideration
particularly where highstrength is also required.
A Study on Mechanical and Tribological Properties of Magnesium Alloy AZ31 Rei...ijsrd.com
This work deals with fabricating or producing magnesium based metal matrix composite and then studying its mechanical and tribological properties such as microstructure, tensile strength, impact strength and wear behavior of produced test specimen. In the present study a modest attempt has been made to develop magnesium based MMCs with reinforcing material, with an objective to develop a conventional low cast method of producing MMCs and to obtain homogeneous dispersion of reinforced material. To achieve this objective stir casting technique has been adopted. An Alloy similar to commercially available composition of AZ31 and SiC, Al2O3 has been chosen as matrix and reinforcing material respectively. Experiment has been conducted by varying weight fraction of 3% SiC and 1% Al2O3 & 1% SiC and 3% Al2O3 in matrix metal. The result shown that tensile strength, impact strength, wear resistance is good in matrix metal as compared to used weight compositions of SiC and Al2O3 in the composites.
Mechanism of Fracture in Friction Stir Processed Aluminium AlloyDr. Amarjeet Singh
Aluminium alloys are used for important
applications in reducing the weight of the component and
structure particularly associated with transport, marine,
and aerospace fields. Grain refinement by scandium (Sc)
addition can eliminate the casting defects and increase the
resistance to hot tearing for high strength aluminium alloys.
FSP for cast aluminium alloys have been focused and it has
great advantages including solid state microstructural
evolution, altering mechanical properties by optimizing
process parameters. These parameters are tool rotational
speeds (720, and 1000 rpm), traverse speeds (80, and 70
mm/min), and axial compressive force at 15 kN, etc. The
mechanical properties had been evaluated on FSPed
aluminium alloy with different microstructural conditions.
Fracture properties of aluminium alloys are very important
for industrial applications. Tensile and fracture toughness
properties were correlated to microstructural and
fractographic features of the aluminium alloys need to
explore their essential failure mechanisms.
Evaluation Of Factors Affecting Sliding Wear Behaviour Of Al-Flyash Metal Mat...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Effect of thermal barrier coating for the improvement of si engine performanc...eSAT Journals
Abstract As per the second law of thermodynamics the efficiency of the engine depends upon the extraction of work against the heat supplied. Minimisation of heat rejection leads to increase the work. Heat rejection takes place through the engine piston, valves and cylinder heads to the surroundings. The aim of the study is to minimise this heat rejection to the surroundings. Heat transfer through the engine parts is minimised by applying the thermal barrier coating materials on the top surface of the engine piston, cylinder heads and valves. In this study an attempt is made to reduce the intensity of thermal and structural stresses by using a layer of the ceramic material, like Yttria stabilized zirconia (YSZ) which has low thermal conductivity, high thermal resistance, chemical inertness, high resistance to erosion, corrosion and high strength was selected as a coating material for engine component. This study present the effect of coating on the piston and the performance of modified four stroke petrol engine and the emission characteristics of the exhaust gas. Key words: Yttrium – zirconium coating, Low heat rejection, Thermal barrier coatings, Engine performance and Emission characteristics
STRUCTURE PROPERTY CORRELATION OF MODIFIED Al-Mg ALLOYS FOR AEROSPACE APPLICA...sivanagaraju chittelu
Making a new metal for Aerospace applications which is made of many components .Major metals are Aluminium and Magnesium.Checking its structures and properties .
Dry Sliding Wear Behaviour of Rheocat Al-5.7Si-2Cu-0.3Mg AlloyDr. Manal Abdullatif
In this study, the effect of improved microstructure of Al-5.7Si-2Cu-0.3Mg alloys by using semisolid process on hardness and dry sliding wear behaviour were investigated. The microstructures of conventional cast alloy were totally dendritic, while in rheocasting the dendrit-ic transfer to fine globular microstructures after using cooling slope casting. Tribological tests were carried out by using a pin-on-disc apparatus in dry sliding conditions. Wear tests were at low sliding speed 1ms-1 ,applied load at 50N and three different sliding distance (i.e., 1.8Km, 5.4Km and 9Km) respectively. An optical microscope and a scanning electron microscope were used to examine the micro-structure and to understand the wear mechanism on the worn surface of both samples. The results showed that, the wear resistance of rheocast alloy was improved and higher than that those produce by conventional casting. The volume loss of rheocast alloy show reduc-tion more than 18% at 1.8Km and 10% at 9Km compared to as-cast alloy. Moderate wear regimes were appeared in both alloys, accord-ing to the range of wear rate. The friction coefficient had increased due to increase in the contact point between pin and disc materials. The dominant wear mechanism for conventional and rheocasting alloys was adhesion wear and abrasive wear respectively.
MICROSTRUCTURAL CHARACTERIZATION AND HOT EROSION BEHAVIOR OF CRC-NICR COATED ...IAEME Publication
Erosion behavior of the High Velocity Oxygen Fuel (HVOF) deposited CrC - NiCr coating on stainless steel was evaluated. Th e solid particle erosion stu dy was conducted using an air jet erosion test rig at a velocity 60m/sec and impingement angle 60 ° , 75 ° and 90 ° , on HVOF spray coated steel at 600 ° C. Microstructure, chemical composition, phases present in the coating on the steel substrate was studied by using Scanning Electron Microscope (SEM) and X - Ray Diffraction method. The Hardness is gradually increasing with increasing content of Cr 3 C 2 particles in all three samples. The erosion mechanism of coatings was also discussed and erosion rate is maximum at impingement angle 75 °
Submission Deadline: 30th September 2022
Acceptance Notification: Within Three Days’ time period
Online Publication: Within 24 Hrs. time Period
Expected Date of Dispatch of Printed Journal: 5th October 2022
MODELING AND ANALYSIS OF SURFACE ROUGHNESS AND WHITE LATER THICKNESS IN WIRE-...IAEME Publication
White layer thickness (WLT) formed and surface roughness in wire electric discharge turning (WEDT) of tungsten carbide composite has been made to model through response surface methodology (RSM). A Taguchi’s standard Design of experiments involving five input variables with three levels has been employed to establish a mathematical model between input parameters and responses. Percentage of cobalt content, spindle speed, Pulse on-time, wire feed and pulse off-time were changed during the experimental tests based on the Taguchi’s orthogonal array L27 (3^13). Analysis of variance (ANOVA) revealed that the mathematical models obtained can adequately describe performance within the parameters of the factors considered. There was a good agreement between the experimental and predicted values in this study.
A STUDY ON THE REASONS FOR TRANSGENDER TO BECOME ENTREPRENEURSIAEME Publication
The study explores the reasons for a transgender to become entrepreneurs. In this study transgender entrepreneur was taken as independent variable and reasons to become as dependent variable. Data were collected through a structured questionnaire containing a five point Likert Scale. The study examined the data of 30 transgender entrepreneurs in Salem Municipal Corporation of Tamil Nadu State, India. Simple Random sampling technique was used. Garrett Ranking Technique (Percentile Position, Mean Scores) was used as the analysis for the present study to identify the top 13 stimulus factors for establishment of trans entrepreneurial venture. Economic advancement of a nation is governed upon the upshot of a resolute entrepreneurial doings. The conception of entrepreneurship has stretched and materialized to the socially deflated uncharted sections of transgender community. Presently transgenders have smashed their stereotypes and are making recent headlines of achievements in various fields of our Indian society. The trans-community is gradually being observed in a new light and has been trying to achieve prospective growth in entrepreneurship. The findings of the research revealed that the optimistic changes are taking place to change affirmative societal outlook of the transgender for entrepreneurial ventureship. It also laid emphasis on other transgenders to renovate their traditional living. The paper also highlights that legislators, supervisory body should endorse an impartial canons and reforms in Tamil Nadu Transgender Welfare Board Association.
BROAD UNEXPOSED SKILLS OF TRANSGENDER ENTREPRENEURSIAEME Publication
Since ages gender difference is always a debatable theme whether caused by nature, evolution or environment. The birth of a transgender is dreadful not only for the child but also for their parents. The pain of living in the wrong physique and treated as second class victimized citizen is outrageous and fully harboured with vicious baseless negative scruples. For so long, social exclusion had perpetuated inequality and deprivation experiencing ingrained malign stigma and besieged victims of crime or violence across their life spans. They are pushed into the murky way of life with a source of eternal disgust, bereft sexual potency and perennial fear. Although they are highly visible but very little is known about them. The common public needs to comprehend the ravaged arrogance on these insensitive souls and assist in integrating them into the mainstream by offering equal opportunity, treat with humanity and respect their dignity. Entrepreneurship in the current age is endorsing the gender fairness movement. Unstable careers and economic inadequacy had inclined one of the gender variant people called Transgender to become entrepreneurs. These tiny budding entrepreneurs resulted in economic transition by means of employment, free from the clutches of stereotype jobs, raised standard of living and handful of financial empowerment. Besides all these inhibitions, they were able to witness a platform for skill set development that ignited them to enter into entrepreneurial domain. This paper epitomizes skill sets involved in trans-entrepreneurs of Thoothukudi Municipal Corporation of Tamil Nadu State and is a groundbreaking determination to sightsee various skills incorporated and the impact on entrepreneurship.
DETERMINANTS AFFECTING THE USER'S INTENTION TO USE MOBILE BANKING APPLICATIONSIAEME Publication
The banking and financial services industries are experiencing increased technology penetration. Among them, the banking industry has made technological advancements to better serve the general populace. The economy focused on transforming the banking sector's system into a cashless, paperless, and faceless one. The researcher wants to evaluate the user's intention for utilising a mobile banking application. The study also examines the variables affecting the user's behaviour intention when selecting specific applications for financial transactions. The researcher employed a well-structured questionnaire and a descriptive study methodology to gather the respondents' primary data utilising the snowball sampling technique. The study includes variables like performance expectations, effort expectations, social impact, enabling circumstances, and perceived risk. Each of the aforementioned variables has a major impact on how users utilise mobile banking applications. The outcome will assist the service provider in comprehending the user's history with mobile banking applications.
ANALYSE THE USER PREDILECTION ON GPAY AND PHONEPE FOR DIGITAL TRANSACTIONSIAEME Publication
Technology upgradation in banking sector took the economy to view that payment mode towards online transactions using mobile applications. This system enabled connectivity between banks, Merchant and user in a convenient mode. there are various applications used for online transactions such as Google pay, Paytm, freecharge, mobikiwi, oxygen, phonepe and so on and it also includes mobile banking applications. The study aimed at evaluating the predilection of the user in adopting digital transaction. The study is descriptive in nature. The researcher used random sample techniques to collect the data. The findings reveal that mobile applications differ with the quality of service rendered by Gpay and Phonepe. The researcher suggest the Phonepe application should focus on implementing the application should be user friendly interface and Gpay on motivating the users to feel the importance of request for money and modes of payments in the application.
VOICE BASED ATM FOR VISUALLY IMPAIRED USING ARDUINOIAEME Publication
The prototype of a voice-based ATM for visually impaired using Arduino is to help people who are blind. This uses RFID cards which contain users fingerprint encrypted on it and interacts with the users through voice commands. ATM operates when sensor detects the presence of one person in the cabin. After scanning the RFID card, it will ask to select the mode like –normal or blind. User can select the respective mode through voice input, if blind mode is selected the balance check or cash withdraw can be done through voice input. Normal mode procedure is same as the existing ATM.
IMPACT OF EMOTIONAL INTELLIGENCE ON HUMAN RESOURCE MANAGEMENT PRACTICES AMONG...IAEME Publication
There is increasing acceptability of emotional intelligence as a major factor in personality assessment and effective human resource management. Emotional intelligence as the ability to build capacity, empathize, co-operate, motivate and develop others cannot be divorced from both effective performance and human resource management systems. The human person is crucial in defining organizational leadership and fortunes in terms of challenges and opportunities and walking across both multinational and bilateral relationships. The growing complexity of the business world requires a great deal of self-confidence, integrity, communication, conflict and diversity management to keep the global enterprise within the paths of productivity and sustainability. Using the exploratory research design and 255 participants the result of this original study indicates strong positive correlation between emotional intelligence and effective human resource management. The paper offers suggestions on further studies between emotional intelligence and human capital development and recommends for conflict management as an integral part of effective human resource management.
VISUALISING AGING PARENTS & THEIR CLOSE CARERS LIFE JOURNEY IN AGING ECONOMYIAEME Publication
Our life journey, in general, is closely defined by the way we understand the meaning of why we coexist and deal with its challenges. As we develop the "inspiration economy", we could say that nearly all of the challenges we have faced are opportunities that help us to discover the rest of our journey. In this note paper, we explore how being faced with the opportunity of being a close carer for an aging parent with dementia brought intangible discoveries that changed our insight of the meaning of the rest of our life journey.
A STUDY ON THE IMPACT OF ORGANIZATIONAL CULTURE ON THE EFFECTIVENESS OF PERFO...IAEME Publication
The main objective of this study is to analyze the impact of aspects of Organizational Culture on the Effectiveness of the Performance Management System (PMS) in the Health Care Organization at Thanjavur. Organizational Culture and PMS play a crucial role in present-day organizations in achieving their objectives. PMS needs employees’ cooperation to achieve its intended objectives. Employees' cooperation depends upon the organization’s culture. The present study uses exploratory research to examine the relationship between the Organization's culture and the Effectiveness of the Performance Management System. The study uses a Structured Questionnaire to collect the primary data. For this study, Thirty-six non-clinical employees were selected from twelve randomly selected Health Care organizations at Thanjavur. Thirty-two fully completed questionnaires were received.
Living in 21st century in itself reminds all of us the necessity of police and its administration. As more and more we are entering into the modern society and culture, the more we require the services of the so called ‘Khaki Worthy’ men i.e., the police personnel. Whether we talk of Indian police or the other nation’s police, they all have the same recognition as they have in India. But as already mentioned, their services and requirements are different after the like 26th November, 2008 incidents, where they without saving their own lives has sacrificed themselves without any hitch and without caring about their respective family members and wards. In other words, they are like our heroes and mentors who can guide us from the darkness of fear, militancy, corruption and other dark sides of life and so on. Now the question arises, if Gandhi would have been alive today, what would have been his reaction/opinion to the police and its functioning? Would he have some thing different in his mind now what he had been in his mind before the partition or would he be going to start some Satyagraha in the form of some improvement in the functioning of the police administration? Really these questions or rather night mares can come to any one’s mind, when there is too much confusion is prevailing in our minds, when there is too much corruption in the society and when the polices working is also in the questioning because of one or the other case throughout the India. It is matter of great concern that we have to thing over our administration and our practical approach because the police personals are also like us, they are part and parcel of our society and among one of us, so why we all are pin pointing towards them.
A STUDY ON TALENT MANAGEMENT AND ITS IMPACT ON EMPLOYEE RETENTION IN SELECTED...IAEME Publication
The goal of this study was to see how talent management affected employee retention in the selected IT organizations in Chennai. The fundamental issue was the difficulty to attract, hire, and retain talented personnel who perform well and the gap between supply and demand of talent acquisition and retaining them within the firms. The study's main goals were to determine the impact of talent management on employee retention in IT companies in Chennai, investigate talent management strategies that IT companies could use to improve talent acquisition, performance management, career planning and formulate retention strategies that the IT firms could use. The respondents were given a structured close-ended questionnaire with the 5 Point Likert Scale as part of the study's quantitative research design. The target population consisted of 289 IT professionals. The questionnaires were distributed and collected by the researcher directly. The Statistical Package for Social Sciences (SPSS) was used to collect and analyse the questionnaire responses. Hypotheses that were formulated for the various areas of the study were tested using a variety of statistical tests. The key findings of the study suggested that talent management had an impact on employee retention. The studies also found that there is a clear link between the implementation of talent management and retention measures. Management should provide enough training and development for employees, clarify job responsibilities, provide adequate remuneration packages, and recognise employees for exceptional performance.
ATTRITION IN THE IT INDUSTRY DURING COVID-19 PANDEMIC: LINKING EMOTIONAL INTE...IAEME Publication
Globally, Millions of dollars were spent by the organizations for employing skilled Information Technology (IT) professionals. It is costly to replace unskilled employees with IT professionals possessing technical skills and competencies that aid in interconnecting the business processes. The organization’s employment tactics were forced to alter by globalization along with technological innovations as they consistently diminish to remain lean, outsource to concentrate on core competencies along with restructuring/reallocate personnel to gather efficiency. As other jobs, organizations or professions have become reasonably more appropriate in a shifting employment landscape, the above alterations trigger both involuntary as well as voluntary turnover. The employee view on jobs is also afflicted by the COVID-19 pandemic along with the employee-driven labour market. So, having effective strategies is necessary to tackle the withdrawal rate of employees. By associating Emotional Intelligence (EI) along with Talent Management (TM) in the IT industry, the rise in attrition rate was analyzed in this study. Only 303 respondents were collected out of 350 participants to whom questionnaires were distributed. From the employees of IT organizations located in Bangalore (India), the data were congregated. A simple random sampling methodology was employed to congregate data as of the respondents. Generating the hypothesis along with testing is eventuated. The effect of EI and TM along with regression analysis between TM and EI was analyzed. The outcomes indicated that employee and Organizational Performance (OP) were elevated by effective EI along with TM.
INFLUENCE OF TALENT MANAGEMENT PRACTICES ON ORGANIZATIONAL PERFORMANCE A STUD...IAEME Publication
By implementing talent management strategy, organizations would have the option to retain their skilled professionals while additionally working on their overall performance. It is the course of appropriately utilizing the ideal individuals, setting them up for future top positions, exploring and dealing with their performance, and holding them back from leaving the organization. It is employee performance that determines the success of every organization. The firm quickly obtains an upper hand over its rivals in the event that its employees having particular skills that cannot be duplicated by the competitors. Thus, firms are centred on creating successful talent management practices and processes to deal with the unique human resources. Firms are additionally endeavouring to keep their top/key staff since on the off chance that they leave; the whole store of information leaves the firm's hands. The study's objective was to determine the impact of talent management on organizational performance among the selected IT organizations in Chennai. The study recommends that talent management limitedly affects performance. On the off chance that this talent is appropriately management and implemented properly, organizations might benefit as much as possible from their maintained assets to support development and productivity, both monetarily and non-monetarily.
A STUDY OF VARIOUS TYPES OF LOANS OF SELECTED PUBLIC AND PRIVATE SECTOR BANKS...IAEME Publication
Banking regulations act of India, 1949 defines banking as “acceptance of deposits for the purpose of lending or investment from the public, repayment on demand or otherwise and withdrawable through cheques, drafts order or otherwise”, the major participants of the Indian financial system are commercial banks, the financial institution encompassing term lending institutions. Investments institutions, specialized financial institution and the state level development banks, non banking financial companies (NBFC) and other market intermediaries such has the stock brokers and money lenders are among the oldest of the certain variants of NBFC and the oldest market participants. The asset quality of banks is one of the most important indicators of their financial health. The Indian banking sector has been facing severe problems of increasing Non- Performing Assets (NPAs). The NPAs growth directly and indirectly affects the quality of assets and profitability of banks. It also shows the efficiency of banks credit risk management and the recovery effectiveness. NPA do not generate any income, whereas, the bank is required to make provisions for such as assets that why is a double edge weapon. This paper outlines the concept of quality of bank loans of different types like Housing, Agriculture and MSME loans in state Haryana of selected public and private sector banks. This study is highlighting problems associated with the role of commercial bank in financing Small and Medium Scale Enterprises (SME). The overall objective of the research was to assess the effect of the financing provisions existing for the setting up and operations of MSMEs in the country and to generate recommendations for more robust financing mechanisms for successful operation of the MSMEs, in turn understanding the impact of MSME loans on financial institutions due to NPA. There are many research conducted on the topic of Non- Performing Assets (NPA) Management, concerning particular bank, comparative study of public and private banks etc. In this paper the researcher is considering the aggregate data of selected public sector and private sector banks and attempts to compare the NPA of Housing, Agriculture and MSME loans in state Haryana of public and private sector banks. The tools used in the study are average and Anova test and variance. The findings reveal that NPA is common problem for both public and private sector banks and is associated with all types of loans either that is housing loans, agriculture loans and loans to SMES. NPAs of both public and private sector banks show the increasing trend. In 2010-11 GNPA of public and private sector were at same level it was 2% but after 2010-11 it increased in many fold and at present there is GNPA in some more than 15%. It shows the dark area of Indian banking sector.
EXPERIMENTAL STUDY OF MECHANICAL AND TRIBOLOGICAL RELATION OF NYLON/BaSO4 POL...IAEME Publication
An experiment conducted in this study found that BaSO4 changed Nylon 6's mechanical properties. By changing the weight ratios, BaSO4 was used to make Nylon 6. This Researcher looked into how hard Nylon-6/BaSO4 composites are and how well they wear. Experiments were done based on Taguchi design L9. Nylon-6/BaSO4 composites can be tested for their hardness number using a Rockwell hardness testing apparatus. On Nylon/BaSO4, the wear behavior was measured by a wear monitor, pinon-disc friction by varying reinforcement, sliding speed, and sliding distance, and the microstructure of the crack surfaces was observed by SEM. This study provides significant contributions to ultimate strength by increasing BaSO4 content up to 16% in the composites, and sliding speed contributes 72.45% to the wear rate
ROLE OF SOCIAL ENTREPRENEURSHIP IN RURAL DEVELOPMENT OF INDIA - PROBLEMS AND ...IAEME Publication
The majority of the population in India lives in villages. The village is the back bone of the country. Village or rural industries play an important role in the national economy, particularly in the rural development. Developing the rural economy is one of the key indicators towards a country’s success. Whether it be the need to look after the welfare of the farmers or invest in rural infrastructure, Governments have to ensure that rural development isn’t compromised. The economic development of our country largely depends on the progress of rural areas and the standard of living of rural masses. Village or rural industries play an important role in the national economy, particularly in the rural development. Rural entrepreneurship is based on stimulating local entrepreneurial talent and the subsequent growth of indigenous enterprises. It recognizes opportunity in the rural areas and accelerates a unique blend of resources either inside or outside of agriculture. Rural entrepreneurship brings an economic value to the rural sector by creating new methods of production, new markets, new products and generate employment opportunities thereby ensuring continuous rural development. Social Entrepreneurship has the direct and primary objective of serving the society along with the earning profits. So, social entrepreneurship is different from the economic entrepreneurship as its basic objective is not to earn profits but for providing innovative solutions to meet the society needs which are not taken care by majority of the entrepreneurs as they are in the business for profit making as a sole objective. So, the Social Entrepreneurs have the huge growth potential particularly in the developing countries like India where we have huge societal disparities in terms of the financial positions of the population. Still 22 percent of the Indian population is below the poverty line and also there is disparity among the rural & urban population in terms of families living under BPL. 25.7 percent of the rural population & 13.7 percent of the urban population is under BPL which clearly shows the disparity of the poor people in the rural and urban areas. The need to develop social entrepreneurship in agriculture is dictated by a large number of social problems. Such problems include low living standards, unemployment, and social tension. The reasons that led to the emergence of the practice of social entrepreneurship are the above factors. The research problem lays upon disclosing the importance of role of social entrepreneurship in rural development of India. The paper the tendencies of social entrepreneurship in India, to present successful examples of such business for providing recommendations how to improve situation in rural areas in terms of social entrepreneurship development. Indian government has made some steps towards development of social enterprises, social entrepreneurship, and social in- novation, but a lot remains to be improved.
OPTIMAL RECONFIGURATION OF POWER DISTRIBUTION RADIAL NETWORK USING HYBRID MET...IAEME Publication
Distribution system is a critical link between the electric power distributor and the consumers. Most of the distribution networks commonly used by the electric utility is the radial distribution network. However in this type of network, it has technical issues such as enormous power losses which affect the quality of the supply. Nowadays, the introduction of Distributed Generation (DG) units in the system help improve and support the voltage profile of the network as well as the performance of the system components through power loss mitigation. In this study network reconfiguration was done using two meta-heuristic algorithms Particle Swarm Optimization and Gravitational Search Algorithm (PSO-GSA) to enhance power quality and voltage profile in the system when simultaneously applied with the DG units. Backward/Forward Sweep Method was used in the load flow analysis and simulated using the MATLAB program. Five cases were considered in the Reconfiguration based on the contribution of DG units. The proposed method was tested using IEEE 33 bus system. Based on the results, there was a voltage profile improvement in the system from 0.9038 p.u. to 0.9594 p.u.. The integration of DG in the network also reduced power losses from 210.98 kW to 69.3963 kW. Simulated results are drawn to show the performance of each case.
APPLICATION OF FRUGAL APPROACH FOR PRODUCTIVITY IMPROVEMENT - A CASE STUDY OF...IAEME Publication
Manufacturing industries have witnessed an outburst in productivity. For productivity improvement manufacturing industries are taking various initiatives by using lean tools and techniques. However, in different manufacturing industries, frugal approach is applied in product design and services as a tool for improvement. Frugal approach contributed to prove less is more and seems indirectly contributing to improve productivity. Hence, there is need to understand status of frugal approach application in manufacturing industries. All manufacturing industries are trying hard and putting continuous efforts for competitive existence. For productivity improvements, manufacturing industries are coming up with different effective and efficient solutions in manufacturing processes and operations. To overcome current challenges, manufacturing industries have started using frugal approach in product design and services. For this study, methodology adopted with both primary and secondary sources of data. For primary source interview and observation technique is used and for secondary source review has done based on available literatures in website, printed magazines, manual etc. An attempt has made for understanding application of frugal approach with the study of manufacturing industry project. Manufacturing industry selected for this project study is Mahindra and Mahindra Ltd. This paper will help researcher to find the connections between the two concepts productivity improvement and frugal approach. This paper will help to understand significance of frugal approach for productivity improvement in manufacturing industry. This will also help to understand current scenario of frugal approach in manufacturing industry. In manufacturing industries various process are involved to deliver the final product. In the process of converting input in to output through manufacturing process productivity plays very critical role. Hence this study will help to evolve status of frugal approach in productivity improvement programme. The notion of frugal can be viewed as an approach towards productivity improvement in manufacturing industries.
A MULTIPLE – CHANNEL QUEUING MODELS ON FUZZY ENVIRONMENTIAEME Publication
In this paper, we investigated a queuing model of fuzzy environment-based a multiple channel queuing model (M/M/C) ( /FCFS) and study its performance under realistic conditions. It applies a nonagonal fuzzy number to analyse the relevant performance of a multiple channel queuing model (M/M/C) ( /FCFS). Based on the sub interval average ranking method for nonagonal fuzzy number, we convert fuzzy number to crisp one. Numerical results reveal that the efficiency of this method. Intuitively, the fuzzy environment adapts well to a multiple channel queuing models (M/M/C) ( /FCFS) are very well.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
2. Installation and Intermittent Characteristics of Reinforced Aluminum Matrix Compositesa
http://www.iaeme.com/IJMET/index.asp 61 editor@iaeme.com
Cite this Article: Singh, K. and Dr. Israr, M. Installation and Intermittent
Characteristics of Reinforced Aluminum Matrix Compositesa. International
Journal of Mechanical Engineering and Technology, 6(7), 2015, pp. 60-73.
http://www.iaeme.com/IJMET/issues.asp?JTypeIJMET&VType=6&IType=7
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2. MATRIX PROPERTIES OF SINTERED DRA MATERIALS
Mostly used alloys in the aircraft industry belong to the Al-Zn-Mg-Cu system.
Usually in these alloys, traces of transient elements (below 1 mass %) such as: Fe, Si,
Co and Ni can also be found. Commercially these alloys are known as 7000 or 7xxx
class. One that has been used for this study is best known as CW67 alloy. Compared
to the Aluminium alloys of the same composition produced by different techniques
(such as melting and casting), sintered alloys have much better properties such as
strength, fracture toughness and stress corrosion resistance (Tietz & Palmour, 1986)
[15]. Mentioned advantages of these alloys can be related to the high amount of fine
secondary precipitates and undiluted dispersed particles It is known that the phase
particles which consist of elements such as Co or Fe+Ni are less prone to coarsening
than the particles consisting of Cr, Ti or Mo (Tietz & Palmour, 1986). Precipitating
phases Co2Al9 and FeNiAl9, which are formed in the Al-Zn-Mg-Cu alloy, are very
fine, ranging from 0.05–2 μm in size. Even finer particles can be produced by forming
the dispersed oxide phase due to presence of oxygen (0.05–0.08 mass %) in this type
of alloy. Increased stress corrosion resistance of sintered DRA is favored by adequate
grain morphology and presence of the higher amount of Co2Al9 precipitates in the
structure [1]. Presence of higher amount of Co has a very big influence on the higher
fatigue resistance values of sintered alloys compared to casted ones (Tietz & Palmour,
1986). In order to obtain finer and more stable structure, a small amount of elements,
such as Zr (0.2–0.8 mass %) can be added. Within casted alloys, amount of Zr cannot
be higher than 0.12 mass %. For further improvement of mechanical properties of
sintered aluminum alloys, mechanical alloying can be applied (Tietz & Palmour,
1986). By performing mechanical alloying, multiple strengthening effects can be
achieved: strengthening of the solid solution (commonly with Mg as an alloying
element), precipitation strengthening and dispersed phase strengthening. It has been
found that higher stress corrosion resistance of mechanically alloyed alloys of 550
MPa and high value of the Young’s modulus of 76.5 GPa compared to other sintered
alloys with values of 310 MPa for the stress corrosion resistance and 73GPa for the
Young’s modulus, make these alloys very interesting candidates for the further
development and characterization.
Improvement of many properties (strength, Young’s modulus, toughness etc.) of
sintered Al-Zn-Mg-Cu alloys compared to the casted ones is achieved by using the
contemporary powder metallurgy techniques. Production of alloy powders by rapid
cooling process (rate of cooling in the range from 104 to 109 K/s), vacuum degassing
of powders or compacts and powder compacting at elevated temperatures (hot
pressing) are just a few of mentioned powder metallurgy techniques which can
improve alloy properties .An initial powder which is used for the production of
sintered aluminium alloys can be made by several techniques, but mostly used one is
pulverization. This technique is equally used in industry and smaller laboratories and
there are several different types of it: gas atomization, ultrasound gas atomization,
splat quenching, melt spinning etc. (Tietz & Palmour, 1986).
3. Karan Singh and Dr. Mohammad Israr
http://www.iaeme.com/IJMET/index.asp 62 editor@iaeme.com
There are two mostly used compaction processes. Both processes consist of
several steps. The first one starts with encapsulation, followed by powder degassing
ending with compaction at higher temperatures (Tietz & Palmour, 1986). In the
second process, powder is iso-staticaly pressed up to 70% of the theoretical density,
degassed and only afterwards compacted at high temperatures up to theoretical
density (Bozic et al., 1997) [2]. Both of these production processes are widely used,
but the first one is more complicated (due to encapsulation/decapsulation), while the
second one is less effective in removal of hydrogen and oxygen originating from the
absorbed moisture in hydrated aluminum oxides. Degassing temperatures are in both
cases in the range from 400 to 500 °C. Powder compaction at elevated temperatures
(up to 500 °C) is done by hot pressing, hot iso-static pressing or hot extrusion which
is mainly used for the production of the final products. By hot pressing at 450 °C
during 2h and applied pressure of 35 MPa, a pore free compact can be produced.
Figure 1 Schematic presentation of high strength aluminum alloys production techniques
(Tietz & Palmour, 1986).
Figure 2 SEM. Aluminum alloy powder (CW67) produced by gas atomization
Primary particle boundaries can be seen in the microstructure of the hot pressed
compacts, and most of the unwanted oxides which are deteriorating mechanical
properties of the materials are located at these places (Gnjidic et al., 2001) [9].
Therefore, it is necessary to deform these materials by hot extrusion or rolling before
use for the high risk applications (Bozic et al., 1997). Since the Al-Zn-Mg-Cu alloy
matrix is the precipitation strengthened alloy, it is important to perform adequate
thermal treatment of the alloy after compaction. This treatment consists of the
solution annealing at 475 °C for 1h followed by water quenching and further ageing at
4. Installation and Intermittent Characteristics of Reinforced Aluminum Matrix Compositesa
http://www.iaeme.com/IJMET/index.asp 63 editor@iaeme.com
120 °C for 24 h or 160 °C for 16h. Mechanism of the thermally induced precipitation
in Al-Zn-Mg-Cu alloys with the high Zn: Mg ratio can be presented in this way:
Saturated solid solution – Gunier-Preston (GP) zones – μ’ (MgZn2) – μ (MgZn2)
Gunier-Preston (GP) zones are precipitating from the saturated solid solution, and
they have coherent interfaces with the parent phase. Semi coherent μ’ (MgZn2) phase
has the monoclinic type of the crystal lattice, while the stable μ(MgZn2) phase has the
hexagonal crystal structure. These phases are precipitating at different temperatures in
the different time interval. When GP zones and the small amount of μ’ (MgZn2) are
present in the structure, alloy exhibits the highest strength values. Addition of Cu
above 1 mass % can also increase the strength (strengthening due to alloying) but the
precipitating mechanism still remains the same. When there is more Cu in the
chemical composition of the alloy, it can be involved in the precipitation by replacing
the Zn atoms.
3. REINFORCING PHASE PROPERTIES OF SINTERED DRA
MATERIALS
Selection of an appropriate composition, morphology and volume fraction of
reinforcing phase is a matter of trade off between the requested mechanical properties
and its economic value. Typical properties which have the biggest effect on the
selection of the particular reinforcing phase are: Young’s modulus value, wear
resistance, fracture toughness, fatigue resistance and thermal expansion coefficient. A
proper choice of the type and geometry of the reinforcing phase is very important for
achieving the best combination of required properties and costs. Mostly used
reinforcing phases for the production of discontinuously reinforced composites are:
SiC in the shape of whiskers, particles of SiC or Al2O3, short Al2O3 or graphite
fibers. Compared to fibers, particles and whiskers are easier for production; they are
less expensive and have stable properties. Whiskers are monocrystalline materials
with a high length/width ratio (50 to 100). This shape of reinforcing phase is mostly
used for composites that will be submitted to extrusion, rolling or forging. Unlike the
particle reinforced composites, materials reinforced with whiskers are slightly less
isotopic and their price is much higher. Reinforcing phase in particle shape is not very
expensive. Maximal/minimal particle dimension ratio is quite low (1 to 5). They have
more isotropic properties compared to whiskers, resulting in better characteristics of
composite materials. This property enables obtaining better characteristics of
composite materials. It is important to know that this type of reinforcing phase is most
commonly made by conventional methods used for the production of the metallic
materials as well. Technical SiC, which is mostly used as a particle reinforcing phase
is often produced by reaction between SiO2 and coke (in excess amount). SiC powder
obtained in this way may still contain a small amount of un-reacted SiO2 or free
graphite Free graphite in a SiC powder can reduce the mechanical properties of the
composites and therefore it has to be removed. Removal of this graphite can be done
by thermal treatment of the powder at 900 °C for 2h (Gnjidic & Bozic, 1999) [8].
Unlike composites produced by melting and casting that consist of particles with
dimensions of hundreds of microns, composites produced by powder metallurgy
techniques can use only much finer particles. Usual size of the SiC particles lies in the
range from submicron size up to around 20 μm As it can be seen from the images, SiC
powder characteristics can differ depending on its particle shape, which can be:
spherical polygonal or irregular with sharp edges.
5. Karan Singh and Dr. Mohammad Israr
http://www.iaeme.com/IJMET/index.asp 64 editor@iaeme.com
4. MIXING PROCESS
Mixing or homogenization of powders is one of the most critical processes in
production of DRA materials by powder metallurgy techniques. If it is done properly,
particles of the reinforcing phase can be uniformly distributed in the composite
metallic matrix which improves the structural and mechanical properties of these
materials. The most important parameters that influence effectiveness of the mixing
process are: mixing dish filling rate, rotation velocity and mixing time (German,
1994) [6]. Optimal values of these parameters are mostly confidential or patent
protected. This means that for every combination of powders (shape, size, amount of
reinforcing phase) and mixing dish type it is necessary to experimentally find optimal
mixing conditions, i.e. optimal values of the previously mentioned parameters. One
method for quantitative analysis of the SiC particle distribution homogeneity is based
on the concept of homogeneity index, Q, which is a quantitative measure of the one
component powder particle distribution homogeneity in the mixture of a few powders
(Gray, 1973) [10]. It should be noted that this concept can only be valid under
assumption that the volume fraction of the observed particles is equal to their surface
fraction. Standard deviation (α) of particle surface measurements is defined by Eq.
ά = 1/N Σ [Ai-Af] (1)
Where N is the number of repeated measurements, Ai is the individual area fraction
and Af is the mean value of all measured particle surfaces. Equation (2) describes the
case in which completely separated system appears (complete segregation) or, in other
words, system in which the whole measuring surface belongs to the particles of just
one powder component.
ά = 2Af (1-Af) (2)
By combining Eqs. (1) and (2), homogeneity index, Q, can be calculated as:
Q= ά/ άseg (3)
Values of homogeneity index vary from 0 (perfect uniform distribution of
particles in the mixture) to 1 (complete non-uniformity of the powder particles).
Using this method, a homogeneity index for all mixtures can be determined by
analyzing the eight randomly chosen measuring fields split into 16 measuring units.
The size of the measuring unit can be calculated from the Eq. (4):
A=1/NA (4)
Where NA is the number of SiC particles in the measuring unit. By using any type of
software for the quantitative analysis of the microstructure, homogeneity of SiC
particle distribution in metal matrix can be calculated (Mc Kimpson et al., 1999) [12].
In our study, which is based on the data found in the literature (German, 1994),
mixing dish rotation velocity was taken to be constant and equal 70 rpm for all
regimes. Beside the rotation velocity, mixing time of 30 min was taken as a constant
for the first five regimes as well. The amount of powders was different and it was
increased by 5 vol. % for each following regime. In the second five regimes, mixing
dish filling rate was kept constant while the time of mixing was changed. The selected
mixing dish filling rate was the optimal value from the first five experimental regimes
.Mixing of powders occurred due to ‘diffusion” in the cylindrical dish without any
6. Installation and Intermittent Characteristics of Reinforced Aluminum Matrix Compositesa
http://www.iaeme.com/IJMET/index.asp 65 editor@iaeme.com
mixing accelerators. Results of quantitative microstructural analysis showing the
effect of the mixing dish filling rate on the homogeneity index values. All mixtures
were well mixed and differences between their homogeneity indexes were in the
range of 15%. Dependence of homogeneity index on the mixing dish filling rate for
three different volume fractions of SiC particles in the mixture exhibits the same
trend. The optimal value was achieved for the mixture with the lowest amount of the
reinforcing phase.
The resulting force that affects particles in powder mixture during mixing is a
result of unified influences of centrifugal, gravitational and frictional forces. The
latter one exhibits the predominant effect on the mixing (homogenization) results. It
was found in this study that optimal mixing dish filling rate was the lowest one (20
vol. %). The reason for this might be the fact that inter-particle contact is minimal
during mixing since the available length for the free fall of particles is maximal, and
therefore, agglomerates are hard to form and the ones already formed can easily be
destructed. With increase of the mixing dish filling rate, amount of SiC powder also
increases forming more agglomerates that need to be destroyed. Available length for
the free fall of particles also decreases resulting in overall decrease in powder mixture
homogeneity. Negative effect of agglomerate presence in the microstructure can also
be increased with the increase of SiC particle amount. It is known that a very large
number of parameters influence the efficiency of particle stacking in the volume of
the powder (Gray, 1973). The most important parameters are shape, size, physical and
chemical characteristics of the powder particles as well as the shape, size and material
of the mixing dish and many more. The real influence of only one parameter is very
hard to predict since it often overlaps with the influence of another one. In the case of
heterogeneous system there is one additional parameter and that is the volume fraction
of the second powder. Higher amount of additional powder decreases the efficiency of
particle stacking but not very dramatically since homogeneity indexes do not differ
much between the different analyzed mixtures.
Table 1 Different mixing regimes for metallic-ceramic composites
Regime
Mixing dish filling rate (vol.
%)
Mixing time (min)
I 20 30
II 25 30
III 30 30
IV 35 30
V 40 30
VI 30 60
VII 30 90
VIII 30 120
IX 30 150
7. Karan Singh and Dr. Mohammad Israr
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Figure 3 Plot of homogeneity index values vs. amount of the mixing dish filling rate for
alloys with a) 0.7 μm and b) 15 μm sized reinforcing powder particles.
It can be noticed that influence of the mixing time on the homogeneity index
values is much higher than the influence of the mixing dish filling rate. Values of
homogeneity index increase up to 40% with the increase of mixing time compared to
the Optimal one. Plots of homogeneity index values vs. mixing time, for the optimal
value of mixing dish filling rate, exhibit the same trend for all mixtures. The best
homogeneity is, like in the previous case, obtained for the mixtures with 5 vol. % SiC.
Mixing time of 60 min was optimal from the aspect of secondary (reinforcing) phase
distribution. It is known that during longer mixing time the effect of particle
“diffusion” is more pronounced (German, 1994). All plots display the increase of
homogeneity index with increase of the amount of reinforcing phase in the mixture
during constant mixing time. That kind of behavior is somewhat expected because of
increase of the number of reinforcing phase particles that need to be mixed a-c and 11
a-c display the microstructures of samples with the optimal homogeneity which are
produced under the optimal mixing conditions and 11 d illustrate so called diffusion
mixing as a result of prolonged mixing time. Scanning electron images clearly show
clusters of SiC as well as areas without SiC presence. SiC powder with medium size
particles of 15 μm, used in this study is characterized by wider particle size
distribution. Around 20 mass.% of this granulation contained particles larger than 20
μm, and a certain percent of 1–2 μm sized particles. Several authors (Flom and
Arsenault, 1989) [5] found that when a SiC particle size is 20 μm or larger, fracture
process changes from mainly matrix controlled failure to particle cracking controlled.
On the other hand, particles of around 1 μm are often prone to agglomeration during
mixing. Therefore, even under optimal mixing conditions, segregation of particles,
presence of surface defects and cracking of large particles can be expected with this
kind of reinforcing material. By sieving this fraction, a powder with the medium size
SiC particles of 10 μm, characterized by the considerably narrower particle size
distribution than the previous one can be extracted.
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Figure 4 LM. Composite microstructure (dSiC=15 μm). a) 5 vol. % SiC, b) 10 vol. % SiC, c)
15 vol. % SiC, and example of prolonged mixing time effect, d) SEM. 15 vol. % SiC, 150
min mixing time.
Figure 5 Plot of homogeneity index values vs. mixing dish filling rate for the alloys with 10
μm size reinforcing phase particles.
Mixing of aluminum alloy and SiC powders was conducted under the same
conditions as in the previous cases in this study. Dependence of the homogeneity
index on the mixing dish filling rate and mixing time. Although the character of the
plots is similar to the previous ones, we can see some differences. In this case, higher
degree of homogenization is achieved and better distribution of reinforcing particles is
observed even for longer mixing times. Microstructures of such mixtures are
presented in a and b.
Figure 6 Plot of homogeneity index values vs. mixing time for the alloys with 10 μm size
reinforcing phase particles.
Different values of mixing dish filling rates and mixing time have great influence
on the SiC particle distribution in aluminum alloy and hence on the mechanical
properties an mechanical behavior of the produced DRA material.
9. Karan Singh and Dr. Mohammad Israr
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5. METHODS OF POWDER MIXTURE CONSOLIDATION
In order to make a fully dense product, powder mixture needs to be consolidated.
Powder metallurgy consolidation techniques consist of three basic steps:
1. Cold isostatic pressing (CIP) – enables formation of compacts with density of 65–
75% of the theoretical density;
2. Compacts degassing at high temperatures-removal of absorbed gases and moisture;
3. Hot or hot vacuum pressing, hot iso-static pressing or hot extrusion – production of
compacts with theoretical density.
Existence of the open porosity in compacts after cold iso-static pressing enables
further vacuum degassing. Degassing temperature is usually in the range from 400 to
500°C. Incomplete degassing results in detaining a large amount of oxides on the
particle surface which cause weaker particle bonding in the following stages of
consolidation process. In this kind of material, formation of cracks and fracture along
the primary particle boundaries is likely to occur. On the other hand, too high
degassing temperatures or very long degassing times are not very favorable since they
can lead to decrease of the Zn amount in the composite matrix (in 7000 alloys).
Mostly used consolidation techniques for production of DRA materials are hot
pressing and hot vacuum pressing. Difference between these two is that in the first
case mixture of powders or porous compact is encapsulated, degassed and then hot
pressed in air, while in the second case degassing is done without encapsulation of the
material just before the hot pressing under vacuum. It is accepted that the latter one
offers better results. To control a large number of parameters and to understand
certain mechanisms of above mentioned processes is very important for the
production of composites. By presenting the densification process with densification
maps it is much easier to comprehend these issues (German, 1996) [7]. Practical value
of these maps is that they link the influence of the crystal structure and atomic bonds
on the plastic flow of the materials. This further enables more simple analysis of
mechanisms which are very important for the experiment design.
Densification maps (Bozic et al., 2009) [3] are determined for the constant
pressure of 35 MPa and for the constant size of matrix powder particles (2R = 125
μm). A model that is used is universal and it allows the comparison of densification
mechanism for different applied pressures and different particle sizes. Other
densification process parameters can easily be changed by changing boundaries
between zones of dominating densification mechanisms. Due to the modular model
structure, complete modulus can be corrected or changed. This fact is particularly
useful since it enables potential corrections of the model. A model used in this study
was made for analyzing different densification mechanisms during the hot pressing,
such as plastic flow, power-law creep and diffusion. From the chosen examples it can
be noted that the process of densification is slowing down as the fraction of the
reinforcing phase increases (slope of the dashed lines) which is in agreement with the
experimental studies. A change in densification mechanism during hot pressing
induced by the change of fraction of reinforcing phase can also be observed from this
maps (different size of the zones for certain densification mechanism). Densification
maps provide a possibility of predicting dominant deformation mechanism,
densification rate and time of pressing for the given conditions of hot pressing
process.
Densification parameters are slightly changed compared to the optimal hot
pressing parameters for the DRA materials production. Poreless structure was
obtained at higher temperature (470 °C) and during longer time (5h). Only under these
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conditions densification can be fully performed when low pressure (35 MPa) is
applied. In the presented case, complete densification was achieved for aluminum
alloy and DRA composite with 15 μm SiC, but not for the composite containing the
smallest (0.7 μm diameter) SiC particles. Microstructures of the hot-pressed
composite materials show that mixing parameters used in the present work enabled
formation of relatively uniformly distributed SiC particles in the aluminum matrix
Porosity existing in the composites reinforced with 0.7 μm SiC, which has been
detected after density measurements illustrated in Formation of agglomerates during
mixing was the primary reason for such behaviour.
Table 2 Densification Parameters
Sample
Theoretical density,
ρt
(g/cm3)
Density, ρ
(g/cm3)
Percentage of
theoretical density
CW67 2.28 2.87 100
CW67-0.7 μm SiC 2.90 2.80 97.5
CW67-15 μm SiC 2.93 2.83 100
6. INFLUENCE OF THE REINFORCING PHASE ON
MECHANICAL AND FRACTURE CHARACTERISTICS OF DRA
MATERIALS
Prior to compressive testing, all hot-pressed materials were subjected to two types of
thermal treatments: under-ageing and peak-aging. Initially, all samples have been
homogenized by solution thermal treatment (1h at 475 °C) followed by water
quenching to room temperature. Under-ageing was performed at 120 °C for 1h, while
the peak-ageing was done at the same temperature of 120 °C for 24h for the CW67
alloy and 22h for the composites. Presence of SiC particles significantly influences
the heterogeneous nucleation of strengthening phases. Capability for heterogeneous
nucleation can be partially attributed to high dislocation density in the composite
matrix, which is present due to the large mismatch between the thermal expansion
coefficients of the matrix and the reinforcing phase. It is well known that dislocations
act as nucleating sites for precipitation during aging, but they also promote
accelerated ageing in the matrix. For that reason, peak-aging conditions for
composites are reached in shorter times than for the monolithic alloy. Influence of
different SiC particle sizes on the yield strength (σyc), ultimate strength (σuc) and
ductility (strain to failure) (ε) under compression at room temperature for both under-
aged (UA) and peak-aged (PA) samples is listed in Values of yield strength (measured
at 0.2 % offset strain) for all composites, irrespective to heat treatment, are higher
than those of the monolithic alloy. On the other hand, the ultimate strength and
ductility values of the composite samples are lower than those obtained for the
unreinforced alloy. It can also be noted that 0.2 % offset strain occurred at much
higher fraction of the total strain-to-failure in the composite than it did in the case of
the CW67 alloy. Main reason for such behavior could be the influence of the SiC
particle sizes, their nature and agglomerate formation. These results also imply that
smaller number of particles is damaged when the applied stress reaches yield stress in
the composites. Stress will continue to accumulate after reaching the yield strength,
leading to rapid failure and therefore low values of the ultimate strength and ductility.
Analysis of results indicates that the samples submitted to peak-aging generally
exhibited higher yield strength and ultimate strength values but also lower ductility
when compared to under-aged samples. The highest compressive property values are
11. Karan Singh and Dr. Mohammad Israr
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obtained for the composite reinforced with 10 μm SiC particles. It is worth noting that
the lowest values are obtained for the composite material with 0.7 μm SiC particles.
This result is unexpected since it is known that particle size decreasing is associated
with improved mechanical characteristics of the particle reinforced composites.
Table 3 Compressive properties of pure aluminum alloy and reinforced materials in
underaged (UA) and peak-aged (PA) conditions
Material σYC (MPa) σUC (MPa) ε (%)
CW67 UA PA UA PA UA PA
CW67-0.7 μm SiC 235 340 860 950 38 35
CW67-10 μm SiC 312 400 720 750 22 19
CW67-15 μm SiC 400 490 850 930 27 23
Generally, mechanical behavior of composites is affected by the presence of
reinforcing particles dispersed in the metal matrix. When analyzing the yield
behaviour of these materials, it is important to recognize that the yielding strength of
the composite is determined by the yield strength of the matrix. Most probably yield
strength may not be the same as yield strength of the monolithic alloy processed and
heat-treated in a similar way (Doel & Bowen, 1996) [4]. The local yield strength of
the matrix may, in fact, be higher than that of the monolithic material due to the
increased dislocation density and reduced grain size. Namely, matrix grain size is
reduced by particles acting as nucleation sites during solidification. Also, grain size is
smaller due to formation of subgrains after dislocation rearrangement into boundaries
within the grain (Rees, 1998) [14]. These subgrains are formed in grains with high
dislocation density surrounding a SiC particle. This rearrangement is a recovery
process driven by the energy stored within the distorted matrix at the interface of two
phases. Also, SiC particles act as obstacles for dislocation motion. There are several
factors affecting the local stress in the matrix. First of all, there is a tensile residual
stress field in the matrix due to the difference in coefficient of thermal expansion
(CTE) between aluminum alloy and SiC. Partial relief of this stress can result in an
increase of dislocation density (Miller & Humphreys, 1991) [13]. Further, any applied
load cannot be evenly distributed between the matrix and the SiC particles because of
difference in stiffness. Several authors have previously reported that the reinforcing
phase can support more applied load than the matrix (Doel & Bowen, 1996). Thus,
local stress in the matrix may be lower than the nominal applied stress. In addition,
SiC particles can withstand this stress until it becomes sufficiently high to cause
particle fracture or failure either at or near the interface. It is believed that damage
will first occur by particle fracture because the interface between SiC particles and
aluminum is very strong. Hence, as soon as the particle breaks the stress in the
undamaged material increases. In time, micro voids are beginning to form in the
matrix as a result of dislocation pile-up, due to the applied load. These voids continue
to grow causing failure of composite materials. In order to comprehend the exact
influence of SiC particle size on the compressive properties of the composite, a
comparison was made between the properties of three composites in both under-aged
and peak-aged condition. Composite sample with 0.7 μm SiC particle size had the
smallest increase of yield strength, presumably due to the presence of the
agglomerates in the structure, originating from the starting powder. In this case,
matrix around the agglomerates is subjected to higher stress because they cannot
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support the same amount of stress as non agglomerated particles. Therefore, matrix is
forced to yield at lower applied stress and, therefore, yield strength of the composites
is also lower. Fracture surface of this composite show evidence of both trans-
crystalline and inter-crystalline fracture mechanisms. A factor that might have a
detrimental effect on the compressive properties of this particular composite material
is the homogeneity of the particle distribution.
Composites reinforced with 10 and 15 μm SiC particles are generally both
stronger and more ductile than the material reinforced with 0.7 μm particles. Of the
two analyzed composites, one containing 10 μm SiC particles has the highest increase
in yield strength and the lowest decrease in ultimate compressive strength and
ductility for both ageing conditions. Main reason for the superior mechanical
characteristics of the medium sized particles composites is uniformity of reinforcing
phase particle dimensions and structure without agglomerates. By making a mixture
with narrower particle size distribution, the number of fracture initiation sites in DRA
material is reduced making the matrix/SiC decohesion a dominant fracture mechanism
Formation of the crack and the crack path depend on the microstructure homogeneity
of the alloys. Uniform path of the existing crack is typical for the less homogenous
alloys, while the zig-zag path characterizes homogenous alloys .The latter type of
crack propagation is a consequence of homogenous distribution of secondary (SiC)
particles.
Figure 7 Fracture surface of DRA materials after 60 min mixing. a) SEM. CW67 - 10 vol.%
SiC, dSiC=10μm; b) LM. CW67 - 10 vol. % SiC, dSiC=10μm.
In the case when the reinforcing particles are not evenly distributed in the alloy
matrix, crack propagates easily through the matrix This behaviour corresponds to poor
mechanical properties of the DRA material with such microstructure. When mixing
time is too long a formation of SiC agglomerates is noticeable. Due to the very weak
bonding between the SiC particles in the agglomerates, a particle decohesion will
easily occur under applied stress and the crack will appear.
As observed by Humphreys (1988), [11] an addition of a brittle reinforcement
phase in high strength aluminum alloys may even decrease the ultimate tensile
strength. Indeed, in the present composites this was found to be the case. Indeed, in
the present composites this was found to be the case. The values of the ultimate
strength were lower than the values for the monolithic material. The presence of SiC
particles can be detrimental to the ultimate compressive strength of the composite
materials because of more additional cracking mechanisms compared to monolithic
alloy. These mechanisms are: particle cracking, particle matrix debonding and particle
agglomerate decohesion. The latter two mechanisms are of a secondary importance
when particles are well distributed and strongly bonded. Thus, it is particle cracking
13. Karan Singh and Dr. Mohammad Israr
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that has a major influence on the ultimate compressive strength of SiC/Al composite
materials. Extensive studies of the room temperature mechanical behavior of these
composites have been conducted, but the information about mechanical properties of
DRA materials at elevated temperatures is still limited. Therefore, some results of the
temperature effect on the compressive properties and fracture behaviour of a SiC
particle reinforced CW67 aluminium alloy will be presented.
With increasing temperature matrix becomes softer and stress accommodation
around the particles caused by difference in CTE becomes easier compared to the
room temperature. The constraint around the particles in the matrix can be relaxed by
a dynamic recovery process. It is therefore expected that any misfit strain gradient can
be relaxed by the recovery process which could lead to a decrease in work hardening
and strength, resulting in a small difference in strength between the composite and the
monolithic alloy at higher temperatures. Increase of composite ductility with
temperature can be a consequence of the improved ductility of the matrix. However,
ductility of the composite is lower than that of the monolithic alloy, which is caused
by the particle cracking or particle matrix debonding effects.
7. CONCLUSIONS
The basic conclusion is that much more research is needed for further enhancement of
the DRA materials properties. Computer simulation and mathematical modeling of
composite fabrication would enable faster achieving of results and therefore these
methods need to be addressed. In this area some scattered work has been done but it
still needs further development. By finding and establishing the proper models actual
experimentation and prediction of properties, shape, size, volume fraction of the
participating phases and mixing parameters would largely be cut down. As mentioned
before, dispersed phase size, shape, volume fraction, wettability and distribution play
the most important role in the properties attained in metal-matrix composites. A lot of
research is focused on optimizing these parameters and based on the results, property
designing of composites is possible. However, all the experimentation has stopped at
decreasing the dispersed phase level below 10μm, possibly due to the difficulty in
dispersing uniformly and without coagulation of finer particles in the matrix. This is
especially pronounced when the liquid metallurgy route is adopted for making the
composites. If the coagulation problem cannot be solved when the particle size is
decreased below 10 μm, alternate methods of fabrication have to be attempted. Most
promising method so far, seems to be in-situ production of composites, which is
recently a very modern trend in science. In the present age of nanomaterials, methods
of dispersion or making composites with nano sized dispersed phase holds a lot of
potential for commercial exploitation in the future.
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