The softening behavior of different cold rolled Al-6Mg alloys containing scandium 0.2 wt% and 0.6 wt% have been investigated by means of microscopy, hardness and electrical conductivity measurements. It is found that the scandium added alloys attend the higher hardness at every state of cold rolling at higher annealed temperature due to the precipitation of scandium aluminides. Electrical resistivity of the scandium added alloys show higher than base alloy due to grain refining. It is seen from the microstructure that scandium refine the grain structure and inhibit recrystallization.
1. Warm rolling of pure iron involves rolling the material in the ferritic phase region between room temperature and the austenite transformation temperature. This results in a two-phase microstructure of ferrite and austenite during deformation.
2. Solute carbon interacts strongly with dislocations during warm rolling, resulting in high strain rate sensitivity and reduced in-grain shear band formation compared to hot or cold rolling. This significantly impacts the development of texture and recrystallization.
3. Warm rolling can produce deep drawing {111} textures traditionally obtained through cold rolling and annealing. Process parameters in warm rolling therefore have a strong influence on recrystallization texture development.
Dispersion Hardening:
Hard particles:
Mixed with matrix powder
Consolidated
Processed by powder metallurgy techniques
Second phase – Very little solubility (Even at elevated temp.)
No coherency
So thermally Stable at very high temp.
Resists :
Grain growth
Over aging
Recrystallization
Mobility of dislocation
Different from particle Metallic Composites (Volume Fraction is 3 to 4% max.) (Does not affect stiffness)
Examples : Al2O3 in Al or Cu, ThO2 in Ni
The document discusses various heat treatment processes used to change the properties and performance of metals. It describes the main stages of heat treatment as heating, soaking, and cooling. Common heat treatment processes include annealing to soften metals, normalizing to refine grains and increase strength, hardening to increase hardness and strength, and tempering to increase toughness after hardening. Specific methods like carburizing, cyaniding, nitriding, and flame hardening are used to case harden metal surfaces. Industries like aerospace, automotive, and defense commonly use heat treating.
The document discusses hardenability, which is the ability of an alloy to form martensite and harden during heat treatment. It can be tested using the Jominy end-quench test, where a bar is heated and quenched at one end in water, causing a gradient of cooling rates and hardness levels along its length. Alloying elements like chromium, molybdenum, and nickel increase hardenability by shifting the CCT diagram to allow more martensite formation at a given cooling rate. The quenching medium, sample size, and alloy composition all impact the hardness profile achieved.
The document discusses various methods for increasing the strength of metals, including hardening, quenching, annealing, tempering, normalizing, and austempering. It provides details on the processes involved and the microstructural and property changes that result from each method. Solid solution strengthening, strain hardening, grain size refinement, precipitation hardening, dispersion hardening, and phase transformations are also summarized as six major mechanisms for increasing metal strength.
1. Warm rolling of pure iron involves rolling the material in the ferritic phase region between room temperature and the austenite transformation temperature. This results in a two-phase microstructure of ferrite and austenite during deformation.
2. Solute carbon interacts strongly with dislocations during warm rolling, resulting in high strain rate sensitivity and reduced in-grain shear band formation compared to hot or cold rolling. This significantly impacts the development of texture and recrystallization.
3. Warm rolling can produce deep drawing {111} textures traditionally obtained through cold rolling and annealing. Process parameters in warm rolling therefore have a strong influence on recrystallization texture development.
Dispersion Hardening:
Hard particles:
Mixed with matrix powder
Consolidated
Processed by powder metallurgy techniques
Second phase – Very little solubility (Even at elevated temp.)
No coherency
So thermally Stable at very high temp.
Resists :
Grain growth
Over aging
Recrystallization
Mobility of dislocation
Different from particle Metallic Composites (Volume Fraction is 3 to 4% max.) (Does not affect stiffness)
Examples : Al2O3 in Al or Cu, ThO2 in Ni
The document discusses various heat treatment processes used to change the properties and performance of metals. It describes the main stages of heat treatment as heating, soaking, and cooling. Common heat treatment processes include annealing to soften metals, normalizing to refine grains and increase strength, hardening to increase hardness and strength, and tempering to increase toughness after hardening. Specific methods like carburizing, cyaniding, nitriding, and flame hardening are used to case harden metal surfaces. Industries like aerospace, automotive, and defense commonly use heat treating.
The document discusses hardenability, which is the ability of an alloy to form martensite and harden during heat treatment. It can be tested using the Jominy end-quench test, where a bar is heated and quenched at one end in water, causing a gradient of cooling rates and hardness levels along its length. Alloying elements like chromium, molybdenum, and nickel increase hardenability by shifting the CCT diagram to allow more martensite formation at a given cooling rate. The quenching medium, sample size, and alloy composition all impact the hardness profile achieved.
The document discusses various methods for increasing the strength of metals, including hardening, quenching, annealing, tempering, normalizing, and austempering. It provides details on the processes involved and the microstructural and property changes that result from each method. Solid solution strengthening, strain hardening, grain size refinement, precipitation hardening, dispersion hardening, and phase transformations are also summarized as six major mechanisms for increasing metal strength.
Strain hardening occurs when dislocations in a deformed metal interact, increasing the material's strength. Deforming a metal increases the number of dislocations, further strengthening the material. Strain hardening is measured by properties like yield strength and tensile strength increasing while ductility decreases. The material becomes harder but more brittle. Annealing can be used to "undo" strain hardening by allowing dislocations to rearrange or new grains to form, restoring ductility at the cost of strength. The annealing process involves recovery, recrystallization and sometimes grain growth, and depends on temperature and time.
The document summarizes an experiment on the effects of cold working and annealing on the hardness of 70-30 brass samples. Cold working the brass samples by rolling them to thinner thicknesses increased their hardness, with hardness rising with increased cold working up to around 35% work. Annealing the cold worked samples reduced their hardness over time, with samples that had received more cold working seeing a greater decrease in hardness during annealing as their structure recrystallized. The experiment supported theories that cold working increases hardness through dislocation formation while annealing reduces hardness through recrystallization and grain growth.
Heat treatment involves heating and cooling metals and alloys to obtain desirable properties or conditions. It includes processes like annealing, normalizing, hardening, and tempering. Heat treatment can relieve stresses, improve machinability and ductility, and make structures more homogeneous.
The document provides an outline on heat treatment processes. It defines heat treatment and its purposes, discusses heat treatment theory and the stages of heat treatment including heating, soaking, and cooling. It describes various heat treatment processes like annealing, normalizing, hardening, and tempering. It also discusses case hardening techniques like carburizing, cyaniding, and nitriding. Finally, it introduces the TTT diagram and the microstructures obtained from different cooling rates.
This document provides information about various heat treatment processes including annealing, normalizing, hardening, tempering, and hardenability. It describes the purposes and procedures for each process, including the effects on microstructure and material properties. Examples are given to illustrate how to determine the final microstructure based on time-temperature treatments using TTT diagrams.
Precipitation hardening involves heating an alloy to dissolve a secondary phase, then quenching to form a supersaturated solid solution. Upon aging at an intermediate temperature, the secondary phase precipitates out of the solution, strengthening the material. The rate of precipitation is fastest at an intermediate temperature, where there is sufficient driving force for precipitation but not too slow diffusion. Precipitation hardening provides a heat treatment method to enhance the hardness of alloys.
Heat treatment involves controlled heating and cooling of metals to alter their properties and is used to improve machining, reduce forming forces, and restore ductility. Key heat treatments include annealing to reduce hardness and residual stresses, normalizing to obtain a uniform structure, and precipitation hardening using a solution treatment, quench, and aging steps. Heat treatment processes are aided by phase diagrams which show temperature effects. Proper design and material selection are important to avoid issues from nonuniform sections or residual stresses during heat treatment.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Heat treatment of Ferrous and Nonferrous metalsmrinalmanik64
Heat treatment involves using heating or cooling to extreme temperatures to achieve desired material properties like hardening or softening. There are several heat treatment processes including annealing, normalizing, case hardening, precipitation strengthening, tempering, austempering, and martempering. The process of hardening steel involves heating the metal to a predetermined temperature for a set time before quenching it in a specified medium according to the defined process.
The document summarizes an experiment to study the effect of artificial aging on the hardness and mechanical properties of Aluminum alloy 7075. Samples of Al 7075 were aged at 320°F for varying time periods from 0 to 48 hours. Hardness tests and tensile tests were performed on the samples before and after aging to determine how properties changed with aging time. Microstructural analysis was also conducted to observe changes in the microstructure. The objective was to determine the optimum aging time that produces maximum strength for the alloy.
Annealing is a heat treatment process used to alter the microstructure of metals to achieve desired properties. It involves heating metals to specific temperatures, holding for a period of time, then slowly cooling. The key stages of annealing are recovery, recrystallization, and grain growth. Recovery relieves internal stresses through dislocation movement. Recrystallization involves nucleation of new strain-free grains. Grain growth increases grain size. Together, these stages reduce hardness and brittleness while increasing ductility. Different annealing types like full annealing, stress relief annealing, and spheroidizing annealing are used to achieve different microstructures and properties for various applications.
The document presents an experimental study on the effects of over-aging on the mechanical properties of 7075 aluminum alloy. Samples were artificially aged at 320°F for varying time periods up to 48 hours. Hardness decreased with increased aging time, with properties like tensile strength and yield strength also generally decreasing due to over-aging. Microstructural analysis showed changes in grain structure with aging. The study evaluated properties like hardness, strength and ductility to analyze the effects of over-aging on 7075 aluminum alloy.
The document discusses various aspects of hardening hypoeutectoid and hypereutectoid steels. It explains that hardening involves heating steel to the appropriate temperature, holding, and then rapidly quenching to form martensite. Factors like chemical composition, part size/shape, heating/cooling rates, and quenchant properties influence the hardening process and final properties. Different hardening methods like direct, stage, and self-tempering quenching are also summarized.
Effect of Subzero Treatment on Microstructure and Material Properties of EN...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness.
Normalizing is a heat treatment process that increases the toughness of steels. It involves heating steel above a certain temperature, soaking, then air cooling to refine the grain structure, relieve internal stresses, and improve toughness. Normalizing produces a finer grain structure and stronger, harder steel compared to annealing, though it is slightly less ductile. It is commonly the last heat treatment applied before use to enhance the mechanical properties of steels.
Conventional heat treatment of low carbon steelAyush Chaurasia
Heat treatment of Low Carbon Steel via heat treatment processes of annealing, quenching and normalising and observing the structural changes affecting the hardness property of material.
Heat treatment is used to alter the physical and mechanical properties of metals through controlled heating and cooling without changing the shape. It involves phase transformations during heating and cooling to modify the microstructure. Common heat treatments include annealing, which involves slowly cooling a heated metal to reduce hardness and increase ductility after cold working, and normalizing, which heats metal to above the critical temperature to dissolve carbides before air cooling. Recrystallization is an important annealing process where new strain-free grains nucleate and grow to replace the deformed microstructure.
Mumbai University
Mechanical engineering
SEM III
Material Technology
Module 1.4
Strain Hardening:
Definition importance of strain hardening, Dislocation theory of strain hardening, Effect of strain hardening on engineering behaviour of materials, Recrystallization Annealing: stages of recrystallization annealing and factors affecting it
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.
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.
Strain hardening occurs when dislocations in a deformed metal interact, increasing the material's strength. Deforming a metal increases the number of dislocations, further strengthening the material. Strain hardening is measured by properties like yield strength and tensile strength increasing while ductility decreases. The material becomes harder but more brittle. Annealing can be used to "undo" strain hardening by allowing dislocations to rearrange or new grains to form, restoring ductility at the cost of strength. The annealing process involves recovery, recrystallization and sometimes grain growth, and depends on temperature and time.
The document summarizes an experiment on the effects of cold working and annealing on the hardness of 70-30 brass samples. Cold working the brass samples by rolling them to thinner thicknesses increased their hardness, with hardness rising with increased cold working up to around 35% work. Annealing the cold worked samples reduced their hardness over time, with samples that had received more cold working seeing a greater decrease in hardness during annealing as their structure recrystallized. The experiment supported theories that cold working increases hardness through dislocation formation while annealing reduces hardness through recrystallization and grain growth.
Heat treatment involves heating and cooling metals and alloys to obtain desirable properties or conditions. It includes processes like annealing, normalizing, hardening, and tempering. Heat treatment can relieve stresses, improve machinability and ductility, and make structures more homogeneous.
The document provides an outline on heat treatment processes. It defines heat treatment and its purposes, discusses heat treatment theory and the stages of heat treatment including heating, soaking, and cooling. It describes various heat treatment processes like annealing, normalizing, hardening, and tempering. It also discusses case hardening techniques like carburizing, cyaniding, and nitriding. Finally, it introduces the TTT diagram and the microstructures obtained from different cooling rates.
This document provides information about various heat treatment processes including annealing, normalizing, hardening, tempering, and hardenability. It describes the purposes and procedures for each process, including the effects on microstructure and material properties. Examples are given to illustrate how to determine the final microstructure based on time-temperature treatments using TTT diagrams.
Precipitation hardening involves heating an alloy to dissolve a secondary phase, then quenching to form a supersaturated solid solution. Upon aging at an intermediate temperature, the secondary phase precipitates out of the solution, strengthening the material. The rate of precipitation is fastest at an intermediate temperature, where there is sufficient driving force for precipitation but not too slow diffusion. Precipitation hardening provides a heat treatment method to enhance the hardness of alloys.
Heat treatment involves controlled heating and cooling of metals to alter their properties and is used to improve machining, reduce forming forces, and restore ductility. Key heat treatments include annealing to reduce hardness and residual stresses, normalizing to obtain a uniform structure, and precipitation hardening using a solution treatment, quench, and aging steps. Heat treatment processes are aided by phase diagrams which show temperature effects. Proper design and material selection are important to avoid issues from nonuniform sections or residual stresses during heat treatment.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Heat treatment of Ferrous and Nonferrous metalsmrinalmanik64
Heat treatment involves using heating or cooling to extreme temperatures to achieve desired material properties like hardening or softening. There are several heat treatment processes including annealing, normalizing, case hardening, precipitation strengthening, tempering, austempering, and martempering. The process of hardening steel involves heating the metal to a predetermined temperature for a set time before quenching it in a specified medium according to the defined process.
The document summarizes an experiment to study the effect of artificial aging on the hardness and mechanical properties of Aluminum alloy 7075. Samples of Al 7075 were aged at 320°F for varying time periods from 0 to 48 hours. Hardness tests and tensile tests were performed on the samples before and after aging to determine how properties changed with aging time. Microstructural analysis was also conducted to observe changes in the microstructure. The objective was to determine the optimum aging time that produces maximum strength for the alloy.
Annealing is a heat treatment process used to alter the microstructure of metals to achieve desired properties. It involves heating metals to specific temperatures, holding for a period of time, then slowly cooling. The key stages of annealing are recovery, recrystallization, and grain growth. Recovery relieves internal stresses through dislocation movement. Recrystallization involves nucleation of new strain-free grains. Grain growth increases grain size. Together, these stages reduce hardness and brittleness while increasing ductility. Different annealing types like full annealing, stress relief annealing, and spheroidizing annealing are used to achieve different microstructures and properties for various applications.
The document presents an experimental study on the effects of over-aging on the mechanical properties of 7075 aluminum alloy. Samples were artificially aged at 320°F for varying time periods up to 48 hours. Hardness decreased with increased aging time, with properties like tensile strength and yield strength also generally decreasing due to over-aging. Microstructural analysis showed changes in grain structure with aging. The study evaluated properties like hardness, strength and ductility to analyze the effects of over-aging on 7075 aluminum alloy.
The document discusses various aspects of hardening hypoeutectoid and hypereutectoid steels. It explains that hardening involves heating steel to the appropriate temperature, holding, and then rapidly quenching to form martensite. Factors like chemical composition, part size/shape, heating/cooling rates, and quenchant properties influence the hardening process and final properties. Different hardening methods like direct, stage, and self-tempering quenching are also summarized.
Effect of Subzero Treatment on Microstructure and Material Properties of EN...IJMER
Cryogenic treatment of steels has been widely used for enhancing mechanical properties
like hardness, toughness and stable metallurgical structure. Application such as gears, kicker rods,
bolts are made of medium carbon alloy steels like EN-24 steel. In these applications, percentage of
retained austenite has considerable effects on the life of the material. A comparative study on
conventionally heat-treated (CHT) and shallow cryogenic treated (SCT) EN-24 steel was done to
evaluate the effect of shallow cryogenic treatment (SCT) on hardness, toughness and the amount of
retained austenite present in the structure of EN24 steel. The microscopic structure of cryogenic
treated EN24 steel revealed the formation of carbides, both primary and secondary carbides. An
estimated amount of 15% retained austenite after CHT tempered condition was less than 2% after SCT
tempered condition. Tensile test fractography of subzero treated (SCT) specimen revealed ductile
fracture. The maximum hardness observed in case of SCT tempered samples was 415BHN, 15%
increase from CHT tempered samples. The maximum impact strength observed in case of SCT
tempered samples was 240kJ/m2, 11% increase from CHT tempered samples. Further SCT tempered
samples, tempered at 650°C resulted in ductility increase by 55% as compared to CHT tempered
samples without sacrificing hardness.
Normalizing is a heat treatment process that increases the toughness of steels. It involves heating steel above a certain temperature, soaking, then air cooling to refine the grain structure, relieve internal stresses, and improve toughness. Normalizing produces a finer grain structure and stronger, harder steel compared to annealing, though it is slightly less ductile. It is commonly the last heat treatment applied before use to enhance the mechanical properties of steels.
Conventional heat treatment of low carbon steelAyush Chaurasia
Heat treatment of Low Carbon Steel via heat treatment processes of annealing, quenching and normalising and observing the structural changes affecting the hardness property of material.
Heat treatment is used to alter the physical and mechanical properties of metals through controlled heating and cooling without changing the shape. It involves phase transformations during heating and cooling to modify the microstructure. Common heat treatments include annealing, which involves slowly cooling a heated metal to reduce hardness and increase ductility after cold working, and normalizing, which heats metal to above the critical temperature to dissolve carbides before air cooling. Recrystallization is an important annealing process where new strain-free grains nucleate and grow to replace the deformed microstructure.
Mumbai University
Mechanical engineering
SEM III
Material Technology
Module 1.4
Strain Hardening:
Definition importance of strain hardening, Dislocation theory of strain hardening, Effect of strain hardening on engineering behaviour of materials, Recrystallization Annealing: stages of recrystallization annealing and factors affecting it
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.
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.
The effect of heat treatment conditions on the mechanical properties of sand ...Vitaly Trostenetsky
The document discusses the effect of heat treatment conditions on the mechanical properties of the sand cast magnesium alloy MRI 202S. It was found that:
1) There is a relatively wide temperature-time window for solid solution treatment and aging that allows achieving an optimal combination of tensile, fatigue, and creep properties.
2) Lowering the solid solution treatment temperature reduces mechanical properties due to less alloying elements remaining in solid solution.
3) Still air cooling induces lower residual stresses than other quenching media like hot water or compressed air.
4) Aging at 250°C for 1 hour after a 495°C solid solution treatment for 9 hours produces similar mechanical properties as the standard heat treatment of
The effect of Deep cryogenic treatment (DCT) on the metallurgical and mechani...Dr.M BALA THEJA
The effect of Deep cryogenic treatment (DCT) on the metallurgical and mechanical properties of Aluminium 6061-T6 is investigated in the present work
The test castings were solutionized at 525°C for 08 hrs and water quenched to room temperature. One set of samples were subjected to cryogenic treatment at -196°C in Cryo- treatment unit, while the other set is subjected to age hardening at 160°C for durations of 3 hrs, 5hrs and 7hrs. Again cryogenic treated specimens were subjected to age hardening at 165°C for durations of 3hrs, 5 hrs and 7hrs. All the samples were taken for Mechanical properties evaluation.
The total duration of the Cryogenic treatment cycle was 36 hrs, which includes 3hrs of cooling from room temperature to -196°C, 24hrs of holding and 09 hrs of warming to room temperature. The Cryogenic treatment was carried out in a specially designed Cryogenic unit
Fundamentals, synthesis and applications of Al2O3-ZrO2 compositesTANDRA MOHANTA
When the word “Ceramic” comes to our mind, we usually associate them with plates, saucers, cups and mugs. But, the word “Ceramic” encompasses more than just the word “plates” or “saucers”. Indeed, ceramic materials are hard and inherently brittle, but this is just the tip of the iceberg. They have multifarious properties and have acquired a status of high technical importance in the field of scientific research. Ceramics are the soul of the modern day’s structural applications owing to their high mechanical and thermal stability under different challenging conditions. They exhibit remarkable properties such as high hardness, high wear resistance, high corrosion resistance, high elastic modulus, high melting point and the ability to retain high strength at elevated temperatures. Alumina (Al2O3) is one such remarkable ceramic material known for its unique optical, mechanical and electrical properties. But the brittle nature of Al2O3 limits its use in certain engineering applications. Therefore, the strength of Al2O3 and Al2O3- based ceramics can be enhanced by tailoring the microstructural design through the application of strategic techniques that may involve secondary phase particle inclusion (such as Zirconia, ZrO2)
Changes in Structural Features of Al-12Si-3Cu Alloy Due to Age HardeningIRJET Journal
The document discusses changes in the structural features of an Al-12Si-3Cu alloy due to artificial age hardening. Samples of the alloy were solutionized at 500°C for 8 hours and quenched before artificial aging at 200°C for varying times. Hardness measurements and optical microscopy observations were performed. Hardness increased with aging time up to a peak of 145 BHN after 12 hours, corresponding to changes in the morphology and size of eutectic Si particles and dissolution of intermetallic phases. The improvement in hardness was attributed to the formation of coherent precipitates during aging that strengthen the alloy.
e-mail [email protected]Effect of Heat Treatment on Some M.docxkanepbyrne80830
*e-mail: [email protected]
Effect of Heat Treatment on Some Mechanical Properties of 7075 Aluminium Alloy
Adeyemi Dayo Isadarea, Bolaji Aremob, Mosobalaje Oyebamiji Adeoyec,
Oluyemi John Olawalec*, Moshood Dehinde Shittuc
aPrototype Engineering Development Institute Ilesa, Nigeria
bCentre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria
cDepartment of Materials Science and Engineering, Obafemi Awolowo University, Ile-Ife, Nigeria
Received: April 14, 2012; Revised: September 3, 2012
This paper reports the effects of annealing and age hardening heat treatments on the microstructural
morphology and mechanical properties of 7075 Al alloy. The material was cast in the form of round
cylindrical rods inside green sand mould from where some samples were rapidly cooled by early
knockout and others gradually cooled to room temperature. From the samples that were gradually
cooled some were annealed while others were age hardened. Both the as-cast in each category and
heat treated samples were subjected to some mechanical tests and the morphology of the resulting
microstructures were characterised by optical microscopy. From the results obtained there is formation
of microsegregations of MgZn
2
during gradual solidification which was not present during rapid
cooling. It was also found out that age hardening and annealing heat treatment operation eliminated
these microsegregations and improve mechanical properties of 7075 Al alloy. It is concluded that
microsegregation can be eliminated by rapid solidification and appropriate heat treatment process.
Keywords: 7075 aluminium, microsegregation, precipitation hardening, annealing, magnesium alloy,
strength
1. Introduction
Aluminium and its alloys are used in a variety of cast and
wrought forms and conditions of heat treatment. For over
70 years, it ranks next to iron and steel in the metal market.
The demand for aluminium grows rapidly because of its
unique combination of properties which makes it becomes
one of the most versatile of engineering and construction
material1-3.
The optimum properties of aluminium are achieved by
alloying additions and heat treatments. This promotes the
formation of small hard precipitates which interfere with
the motion of dislocations and improve its mechanical
properties4-7. One of the most commonly used aluminium
alloy for structural applications is 7075 Al alloy due to its
attractive comprehensive properties such as low density, high
strength, ductility, toughness and resistance to fatigue8-11. It
has been extensively utilized in aircraft structural parts and
other highly stressed structural applications12-16.
But aluminium-zinc alloy as it is in 7075 Al alloy is
susceptible to embrittlement because of microsegregation
of MgZn
2
precipitates which may lead to catastrophic
failure of components produced from it17,18. The alloy is also
susceptibility to stress corrosion cracking19,20. This is .
Wear Properties of Thixoformed Al-5.7Si-2Cu-0.3Mg Aluminium AlloyDr. Manal Abdullatif
Earlier work has shown that Al-5.7Si-2Cu-0.3Mg aluminium alloy is suitable for
thixoforming process. Here, the dry sliding wear behaviour of the alloy, in the as-cast and
thixoformed conditions were investigated. The cooling slope technique was used to produce the alloy
with globular microstructure for the thixoforming process. Both the thixoformed and cast samples
were subjected to T6 heat treatments prior to the wear tests. The tests were carried out using a
pin-on-disc tribometer, against a hardened M2 tool steel disc of 62 HRC at different loads, under dry
sliding conditions at fixed sliding speed and sliding distance of 1 m.s–1 and 5 km respectively. The
microstructural response, worn surfaces was thoroughly and carefully examined using various
methods such as scanning electron microscopy, energy dispersive spectroscopy, and differential
scanning calorimetry. The density of the heat treated thixoformed alloys showed significant increase
in the hardness property, among others, due to its reduced porosity. Their wear test results also
observed that the weight loss of materials increase with an increase in the input load and the sliding
distance for all samples. However, the as-cast alloy displayed higher wear rate compared with the
thixoformed alloys. In general, the wear mechanisms showed a mixture of abrasive, oxidative and
delamination wear (mild wear) at low applied loads and mainly an adhesive (severe wear) at high
applied loads.
This document discusses the effects of heat treatment on the microstructure and mechanical properties of gray cast iron. It finds that hardening gray cast iron through quenching increases its hardness significantly compared to the as-received material due to the formation of martensite. Hardening and tempering gray cast iron results in a slight decrease in hardness compared to just hardening, as tempering allows some graphite flakes to reform. Microstructural analysis shows hardened gray cast iron has a martensitic needle-like structure instead of graphite flakes, accounting for the increase in hardness.
Annealing and Microstructural Characterization of Tin-Oxide Based Thick Film ...Anis Rahman
Abstract. The sheet resistance of tin oxide based thick-film resistors exhibits two regions of temperature dependence,
described by hopping (23°C-200°C) and diffusion mechanisms (200°C-350°C), respectively.
Annealing these samples causes the sheet resistance to increase in both regions. In the post-annealed samples,
the hopping conduction range is extended by 50°C (23°C-250°C) while the hopping parameter, To, is decreased by
more than 50%. The activation energy of diffusion (0.60 eV) is the same for both pre- and post annealed samples, but
the magnitude of resistance in the diffusion controlled region is increased significantly as a result of annealing. These
changes are explained in terms of a net decrease in the concentration of tin ions in the glass matrix. From a careful
microstructural study it was found that a conduction path composed of tin-oxide grains or their clusters in contact
with each other does not exist in the present system. HREM micrographs showed the presence of nanocrystalline
tin-oxide particles in the glass phase separating the tin-oxide grain clusters. Estimated average separation between
the nanocrystals in 4 nm, consistent with a variable-range hopping conduction via the dissolved tin ions in the glass
matrix.
The International Journal of Engineering and Science (The IJES)theijes
This document discusses the influence of welding conditions on the mechanical properties of welded joints of 9% nickel steel used for liquefied natural gas (LNG) tanks. Specifically, it examines the effect of heat input between 1.4-2 Kj/mm and controlling interpass temperature below 80°C on the tensile strength and toughness of the welded joints. The study found that these welding parameters improved the strength and reduced the probability of brittle fracture in the welded joints of thin 9% nickel steel specimens. Controlling heat input and temperature during welding is important for maintaining the desired microstructure and mechanical properties of the welded joints.
The document discusses processing techniques for AZ31 magnesium alloy and their effects on microstructure and mechanical properties. It covers bulk deformation techniques like rolling (hot, cold, cryogenic) and extrusion (hot, cold), as well as severe plastic deformation techniques like equal channel angular pressing. Rolling and extrusion are used to refine grains and reduce defects at different temperatures. Severe plastic deformation can produce submicron grains to greatly improve strength according to the Hall-Petch relation. Processing parameters like temperature, strain rate, and number of passes are important to optimize microstructure and mechanical properties for magnesium alloys.
This experiment studied the precipitation hardening behavior of an Al-4%Cu alloy by measuring changes in hardness over time during artificial and natural aging. Artificial aging at 190°C produced maximum hardness after 10 minutes that decreased after 1 week as precipitates coarsened. Natural aging reached maximum hardness more slowly over 1 week. Maintaining the alloy at 190°C could lead to precipitate coarsening and hardness loss over time.
This document discusses wrought magnesium alloys, including their composition, processing methods, and deformation behavior. It notes that magnesium alloys have low workability at room temperature due to their HCP crystal structure, but can be processed at temperatures above 300°C. The effects of temperature and strain rate on the microstructure and mechanical properties of AZ31 magnesium alloy during hot rolling are examined. Creep behavior is also discussed, noting the different creep stages and that magnesium alloys have limited creep resistance above 200°C due to their tendency to oxidize.
Microstructure and tribological properties of nanoparticulate wcIAEME Publication
The document summarizes a study on the microstructure and tribological properties of aluminum metal matrix composites reinforced with tungsten carbide nanoparticles. Nanoparticulate WC/Al composites were fabricated using vacuum melt processing. Sliding wear tests found that adding WC nanoparticles effectively reduced the frictional coefficient and wear rate of the composites compared to the unreinforced aluminum alloy. Examination of worn surfaces using SEM suggested the nanoparticles promote a positive rolling effect that improves the load carrying capacity of the nanocomposites.
Reducing Corrosion Rate by Welding DesignIJERD Editor
This document summarizes a study on reducing corrosion rates in steel through welding design. The researchers tested different welding groove designs (X, V, 1/2X, 1/2V) and preheating temperatures (400°C, 500°C, 600°C) on ferritic malleable iron samples. Testing found that X and V groove designs with 500°C and 600°C preheating had corrosion rates of 0.5-0.69% weight loss after 14 days, compared to 0.57-0.76% for 400°C preheating. Higher preheating reduced residual stresses which decreased corrosion. Residual stresses were 1.7 MPa for optimal X groove and 600°C
This document summarizes the manufacturing and testing of iron-aluminum superalloy samples. It discusses that samples with varying iron-aluminum compositions were manufactured using powder metallurgy. The samples were then subjected to cyclic high temperature oxidation testing up to 900°C for 5 cycles. The samples demonstrated improved oxidation resistance compared to normal alloys, forming a protective aluminum oxide layer. Graphs show the weight gain of three samples over the cycles, with sample C exhibiting the lowest cumulative weight gain.
This document summarizes the manufacturing and testing of iron-aluminum superalloy samples. It discusses that samples with varying iron-aluminum compositions were manufactured using powder metallurgy. The samples were then subjected to cyclic high temperature oxidation testing up to 900°C for 5 cycles. The samples demonstrated improved oxidation resistance compared to normal alloys, forming a protective aluminum oxide layer. Graphs show the cumulative weight gain of 3 samples over the cycles.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
Preparation and Investigation on Properties of Cryogenically Solidified Nano ...IJERA Editor
In the present work, AL-alloy containing 12% silicon (LM 13) matrix nano composites were fabricated in sand moulds by using copper end blocks of copper end chill thickness 10 &15 nm with cryogenic effect . The size of the reinforcement (NanoZro2) ranges from 50-80nm being added ranges from 3 to 15 wt % in steps of 3 wt % . Cryogenically solidified Nano Metal Matrix Composites were compressed by using hydraulic compression machine. Specimens were prepared according to ASTM standards and tested for their strength, hardness and fracture toughness. Micro structural studies of the fabricated Nano Composites indicate that there is uniform distributions of reinforcements in the matrix materials (LM 13). An increasing trend of hardness, UTS & fracture toughness has been observed. The best results have been obtained at 12 wt %. The results were further justified by comparing two copper end chill thickness 10 &15 mm. Finally the Volumetric Heat Capacity of the cryo-chill is identified as an important parameter which affects mechanical properties.
Similar to Effect of Scandium on the Softening Behaviour of Different Degree of Cold Rolled Al-6mg Alloy Annealed at Different Temperature (20)
Modelling and Simulation of Composition and Mechanical Properties of High Ent...msejjournal
Magnesium alloys are high potential materials for application in the aerospace and automotive industries
due to their lightweight properties. They can help to lower dead weight and fuel consumption to contribute
to sustainability and efficiency. It is possible to achieve high specific strength and high stiffness of the
alloys by varying compositions of alloying elements. Applications of magnesium are limited due to its low
strength and relatively low stiffness. This research focuses on a recipe of multi component alloys of
magnesium with varied percentages of Mg, Al, Cu, Mn and Zn obtained from literature and optimizes the
percentage compositions to obtain for high specific strength and specific stiffness. Relationships among
percentage constituents of the alloy components are examined in Matlab R2022b using multiple linear
regression. Optimization is achieved using genetic algorithm to determine the specific strengths and
stiffness. The resulting optimal alloy component percentages by weight are used for microstructure
simulation of thermodynamic properties, diffusion and phase transformations of proposed alloy is done in
MatCalc software version 6.04. Results show potential for improved mechanical properties resulting from
disordered structure in the high entropy magnesium alloy. Future research should focus on production and
characterization of the proposed alloy.
Thermal and Metrological Studies on YTTRIA Stabilized Zirconia Thermal Barrie...msejjournal
Thermal Barrier Coatings (TBCs), routinely prepared from Ceramic based compositions (typically
8%Y2O3-ZrO2or 8YSZ) are being engineered to protect the metallic components from degradation in
applications like gas turbines, jet and automotive engines. With a goal of finding improved TBC materials
a wide variety of ceramics are being researched worldwide. Before physically preparing the TBCs of
uncommon compositions in the laboratory, their suitability to perform can be predicted. Limited
accessibility to detailed and realistic information on the influence of newer compositions (other than 8YSZ)
on TBCs warrants methods to obtain this information.
In this paper, 8YSZ TBCs coated onto aluminium substratesare studied for thermal fatigue, thermal barrier
and materials characteristics to determine the reliability of the coating configuration to withstand the
harshness of test conditions under the framework of experiments. Thereafter, the results have been used to
corroboratethe developed simulation model. Results obtained via thermal tests confirm the suitability of the
model and we can predict the thermal barrier effects of TBCs when prepared from materials other than
YSZ.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly peer-reviewed journal that publishes articles on theoretical and practical aspects of materials science and engineering. The goal of the journal is to bring together researchers and practitioners from academia and industry to focus on advancements in materials science and engineering and establish new collaborations. Original research papers and review articles are invited for publication in areas including biomaterials, composites, nanomaterials, and polymers.
New Experiment System for the Interaction Between Soft Rock and Water : A Cas...msejjournal
The strength of rock strongly depends on the water content especially when the rocks contain clay
materials. The interaction between soft rock and water always threaten the soft rock engineering projects.
For this problem, new sets of laboratory experiment systems are developed to simulate the interaction
between soft rock and water or vapor. In this paper, the principles of experiment systems are introduced
with particular reference to the application on soft rock in Mogao Grottoes, one of the world famous
ancient sites in China. Two kinds of rock samples, the sandstone and muddy sandstone, are obtained by insitu sampling system. Then the laboratory experiments are performed under different environment
conditions. By the specific boundary conditions design, the physical-chemical effect and mechanic effect on
water absorption of rock samples are separated for further mechanism study by the experiment system, and
the different hydrological actions of water and vapor under variable experiment environment are obtained.
The interaction mechanism is discussed with assistant methods, such as SEM (Scanning Electron
Microscope), mercury injection test, X-ray diffraction analysis and etc. With the relation between water
content and soft rock strength, the study may provide guidance and basis for the soft rock engineering in
the future.
International Conference on Embedded Systems and VLSI (EMVL 2023)msejjournal
International Conference on Embedded Systems and VLSI (EMVL 2023) will provide an excellent International forum for sharing knowledge and results in theory, methodology and applications of Embedded Systems.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
Modeling, Analyzing and Safety Aspects of Torsion and Noise Effects on Round ...msejjournal
Each material has its own effect and behavior on external impacts like heat, force, tension, compression,
torsion etc. It is important to study and analyze these behaviors before selecting a material for an
engineering application in the design aspects itself. If predicted values analyzed by both mathematical and
software are available it is easy to get the reliable details in the pre design itself. By this one can ensure the
safety of the component and the system also. In this investigation, the effects of torsional loads on mild steel
round shafts with various diameters and lengths have been analyzed. The additional effects like angle of
rotation, rpm and duration also considered to find the optimum predicted value. The data observed by
various experiments are analyzed by design of experiments especially by response surface methodology.
Minitab software is used for canalization. The data are tabulated and kept for future reference. Noise effect
due to the gradual torsional load performed in the gear box and other rotating components is also studied
for healthy working environment. The nature and characteristics of material also be explained by this noise
analysis.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
On Decreasing of Dimensions of Field-Effect Transistors with Several Sourcesmsejjournal
We analyzed mass and heat transport during manufacturing field-effect heterotransistors with several
sources to decrease their dimensions. Framework the result of manufacturing it is necessary to manufacture
heterostructure with specific configuration. After that it is necessary to dope required areas of the heterostructure by diffusion or ion implantation to manufacture the required type of conductivity (p or n). After
the doping it is necessary to do optimize annealing. We introduce an analytical approach to prognosis mass
and heat transport during technological processes. Using the approach leads to take into account nonlinearity of mass and heat transport and variation in space and time (at one time) physical parameters of these
processes
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Using Advanced Inspection Method (Three-Dimensional Ultrasonic) in Recognitio...msejjournal
In this study, using Harfang Code 32 device, the slag catcher pipelines in one of the South Pars phases
were tested. In radiography method of these lines, no clear defect was observed in radiographic films due
to the high thickness of 40 mm. However, marvelous results were obtained using advanced ultrasonic.
Review and analysis of the results will result in high potential of three-dimensional ultrasonic method in
identifying defects in pipelines with high thicknesses and preventing financial and life-threatening risks
during the use of these refineries in the future.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
RESULTS OF FINITE ELEMENT ANALYSIS FOR INTERLAMINAR FRACTURE REINFORCED THERM...msejjournal
The double cantilever beam (DCB) is widely used for fracture toughness testing and it has become popular
for opening-mode (mode I) delamination testing of laminated composites. Delamination is a crack that
forms between the adjacent plies of a composite laminate at the brittle polymer resin. This study was
conducted to emphasize the need for a better understanding of the DCB specimen of different fabric
reinforced systems (carbon fibers) with a thermoplastic matrix (EP, PEI), by using the extended finite
element method (X-FEM). It is well known that in fabric reinforced composites fracture mechanisms
include microcracking in front of the crack tip, fiber bridging and multiple cracking, and both contribute
considerably to the high interlaminar fracture toughness measured. That means, the interlaminar fracture
toughness of a composite is not controlled by a single material parameter, but is a result of a complex
interaction of resin, fiber and interface properties.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Flammability Characteristics of Chemical Treated Woven Hemp Fabricmsejjournal
Woven hemp fabric was treated with sodium hydroxide, commercial flame retardant chemical, and
combination of both to increase its fire-retardant properties. Treatments of fire-retardant changed the
properties of woven hemp fabric such as increased its fabric shrinkage and density of fibres which ranges
from 0.67 to 5% and 1.43 to 1.53 g/cm3
respectively. After the treatment, the fire retardancy of the fabric
increased tremendously which was observed by the burning, thermogravimetry and limiting oxygen index
tests. Some of the samples were not burnt when exposed to flame source and the burning rate needed to be
measured under exaggeration of flame at longer time. The limiting oxygen index value increased from 18.6
to 51 after the treatments which explained the scenario happened in the burning tests. Nevertheless, its
mechanical properties decreased slightly that ranges from 18 to 32% and 23 to 39% for warp and weft
respectively compared to untreated fibre.
Advances in Materials Science and Engineering: An International Journal (MSEJ) msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Advances in Materials Science and Engineering: An International Journal (MSEJ) msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Advances in Materials Science and Engineering: An International Journal (MSEJ)msejjournal
Advances in Materials Science and Engineering: An International Journal (MSEJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Materials Science and Engineering. The journal is devoted to the publication of high quality papers on theoretical and practical aspects of Materials Science and Engineering.
The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on Materials Science and Engineering advancements, and establishing new collaborations in these areas. Original research papers, state-of-the-art reviews are invited for publication in all areas of Materials Science and Engineering.
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
in Central Asia. This study adheres to the empirical epistemological method and has taken care of
objectivity. This study analyze primary and secondary research documents critically to elaborate role of
china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
artificial intelligence and data science contents.pptxGauravCar
What is artificial intelligence? Artificial intelligence is the ability of a computer or computer-controlled robot to perform tasks that are commonly associated with the intellectual processes characteristic of humans, such as the ability to reason.
› ...
Artificial intelligence (AI) | Definitio
Software Engineering and Project Management - Introduction, Modeling Concepts...Prakhyath Rai
Introduction, Modeling Concepts and Class Modeling: What is Object orientation? What is OO development? OO Themes; Evidence for usefulness of OO development; OO modeling history. Modeling
as Design technique: Modeling, abstraction, The Three models. Class Modeling: Object and Class Concept, Link and associations concepts, Generalization and Inheritance, A sample class model, Navigation of class models, and UML diagrams
Building the Analysis Models: Requirement Analysis, Analysis Model Approaches, Data modeling Concepts, Object Oriented Analysis, Scenario-Based Modeling, Flow-Oriented Modeling, class Based Modeling, Creating a Behavioral Model.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
The CBC machine is a common diagnostic tool used by doctors to measure a patient's red blood cell count, white blood cell count and platelet count. The machine uses a small sample of the patient's blood, which is then placed into special tubes and analyzed. The results of the analysis are then displayed on a screen for the doctor to review. The CBC machine is an important tool for diagnosing various conditions, such as anemia, infection and leukemia. It can also help to monitor a patient's response to treatment.
Comparative analysis between traditional aquaponics and reconstructed aquapon...bijceesjournal
The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
Effect of Scandium on the Softening Behaviour of Different Degree of Cold Rolled Al-6mg Alloy Annealed at Different Temperature
1. Advances in Materials Science and Engineering: An International Journal (MSEJ), Vol. 1, No. 1, September 2014
39
EFFECT OF SCANDIUM ON THE SOFTENING
BEHAVIOUR OF DIFFERENT DEGREE OF COLD
ROLLED AL-6MG ALLOY ANNEALED AT
DIFFERENT TEMPERATURE
M. S. Kaiser
Directorate of Advisory, Extension and Research Services
Bangladesh University of Engineering and Technology, Dhaka- 1000, Bangladesh
ABSTRACT
The softening behavior of different cold rolled Al-6Mg alloys containing scandium 0.2 wt% and 0.6 wt%
have been investigated by means of microscopy, hardness and electrical conductivity measurements. It is
found that the scandium added alloys attend the higher hardness at every state of cold rolling at higher
annealed temperature due to the precipitation of scandium aluminides. Electrical resistivity of the
scandium added alloys show higher than base alloy due to grain refining. It is seen from the microstructure
that scandium refine the grain structure and inhibit recrystallization.
KEYWORDS
Al-Mg alloys, microstructure, cold rolling, annealing, electrical resistivity
1. INTRODUCTION
Technically pure aluminium has good formability, good thermal conductivity but very little
strength. Increasing the strength of aluminium can be achieved in several ways: by solid-solution-
hardening, precipitation-hardening or by refinement of grains, creating a fine and even ultrafine
grains microstructure [1-3]. However, precipitation-hardening is the most effective method. This
type of hardening is often used in aluminum alloys containing copper, magnesium, chromium,
lithium, zinc etc. [4, 5]. Precipitations coherent with the matrix which are located inside the
grains are the most effective. Due to the different methods of production of aluminum
components casting, extrusion, rolling or processing the creation of an optimum microstructure in
a single technology process is extremely difficult and additional heat treatment is necessary [6-8].
The most commonly given information applies only to the temperature range of super saturation
and aging, but it does not give time specifications of the aging process. It is very important to
note that too long artificial aging can lead to so-called over aging i.e. decreased strength and
hardness of the material as a result of mostly coagulation of the precipitates. The knowledge of
the recommended treatment temperature as well as the time of this process are essential for
optimum hardening results. With regard to the ranges of the heat treatment temperature,
deviations from specified ranges and the impact of the implementation of treatment at a slightly
higher or slightly lower temperature should be known. Mg is the principal alloying element and is
added for solid solution strengthening [9]. The Al-Mg alloys have a favorable formability, as due
solution hardening they can achieve high strength and high strain hardening ability, which enable
a stable behavior in the complex forming operation, reducing the further material flow in the
locally strained regions [10, 11].
2. Advances in Materials Science and Engineering: An International Journal (MSEJ), Vol. 1, No. 1, September 2014
40
The use of scandium as an alloying element in aluminium has gained an increasing interest even
though scandium is difficult to extract, which makes the metal very expensive. The three
principle effects that can be obtained by adding scandium to aluminium alloys are (i) grain
refinement during casting or welding, (ii) precipitation hardening from Al3Sc particles and (iii)
grain structure control from Al3Sc dispersoids [3].
Al-Mg alloy is normally used in a work-hardened condition and will undergo softening during
use. But the softening behavior of the alloy system under the influence of Al3Sc particles pre-
existing in the matrix has not been studied elaborately. The aim of this work was to determine the
softening behavior of cold rolled Al-6Mg alloys doped with scandium 0.2 wt% and 0.6 wt%.
Since cold working introduces huge dislocations, it is a question to resolve if the presence of
dislocations has any role on the precipitation behavior of Al3Sc during annealing of the Al-Mg-Sc
alloy.
2. EXPERIMENTAL
Melting was carried out in a resistance heating pot furnace under the suitable flux cover
(degasser, borax etc.). Several heats were taken for developing base Aluminium-Magnesium alloy
and Aluminium-Magnesium alloy containing scandium at various levels. In the process of
preparation of the alloys the commercially pure aluminium (99.5% purity) was taken as the
starting material. First the aluminium and aluminium-scandium master alloy (2%Sc) were melted
in a clay-graphite crucible, then magnesium ribbon (99.7% purity) was added into solution. The
final temperature of the melt was always maintained at 780±15o
C with the help of the electronic
controller. Variation of the scandium percentage was accomplished by its respective additions of
master alloy. Casting was done in 12.5mm x 50mm x 200mm cast iron metal mould preheated to
200o
C. The alloy was analysed by chemical and spectrochemical methods simultaneously. The
chemical compositions of the alloys are given in Table 1. The cast samples were first ground
properly to remove the oxide layer from the surface. Cold rolling of the alloy, as cast was carried
out with a laboratory scale rolling mill of 10HP capacity at deferent percentages of reduction. The
samples in as cast and cold rolled were annealed isochronally at various temperatures for one
hour ranging from 100o
C to 500o
C. Vickers hardness of differently processed alloys was
measured with a 5 kg load for assessing the softening effect of the alloy. An average of seven
consistent readings was accepted as the representative hardness value of an alloy. Electrical
conductivity of the alloys as cast and cold worked with different deformation percentages, were
measured. Surface finished samples of area 12 mm x 12 mm, were subjected to conductivity test
using a Conductivity Meter, Type 979. Electric resistivity was then calculated from the measured
values of conductivity. The cold rolled alloys after different heat treatments are subjected to
optical metallographic studies. The specimens were polished with alumina and etched with
Keller’s reagent and observed under a Versamet-II- Microscope. Scanning electron microscopy of
the selected samples was carried out by a Jeol Scanning Electron Microscope, JSM-5200.
Transmission Electron Microscopic studies of the alloy was carried out in Philips (CM12)
Transmission Electron Microscope at an accelerating voltage 160 KV.
Table 1. Chemical Composition of the Experimental alloy (wt%)
Alloy Mg Sc Zr Ti Cu Fe Mn Ni Si Zn Al
1 6.10 0.000 0.000 0.001 0.081 0.382 0.155 0.003 0.380 0.136 Bal
2 5.90 0.200 0.001 0.002 0.081 0.345 0.132 0.003 0.360 0.174 Bal
3 6.02 0.600 0.001 0.003 0.061 0.293 0.086 0.002 0.320 0.126 Bal
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41
3. RESULTS
3.1. Isothermal Annealing
The results of isochronal annealing of all the three cast alloys at different temperature for 1 hour
are shown in Figure 1. It is seen that all the alloys except base alloy (alloy 1) have shown
appreciable precipitation hardening response. Alloy 1 has however shown a continuous softening
at increasing annealing temperatures, with a steeper hardness drop beyond 400o
C. However a
distinct rise in peak hardness of the alloys is observed for increase in scandium content from 0.2
wt% and 0.6 wt%. In all cases the peak hardness is obtained at around 300o
C. Beyond peak
hardness value the usual softening due to annealing takes place. On close observation of the
variation of hardness in over aged situation, it appears that alloy 3 with 0.6 wt% Sc possesses
maximum resistance to age softening.
40
50
60
70
80
90
100
0 100 200 300 400 500
Annealing temperature, o
C
Hardness,VHN
Alloy 1
Alloy 2
Alloy 3
Figure 1. Isochronal annealing curve of the cast alloys annealed for 1 hour.
The results of isochronal annealing of the cold worked alloys at different temperature for 1 hour
show identical nature of precipitation hardening at different deformation percentages (Figures 2-
4). The initial hardness is higher for higher amount of deformation for all the alloys. The base
alloy (alloy 1) shows a continuous softening due to recovery and recrystallisation of the strained
grains. All other alloys demonstrate precipitation hardening response with peak hardness value at
300o
C. An initial softening to the tune of 5 VHN is noted in almost all the alloys. The extent of
age hardening varies with the composition of the alloy; however alloy 3 shows maximum
hardness at all deformations. The hardness value of all the alloys at peak-aged condition is seen to
be increased with increasing amount of deformation. The extent of precipitation hardening does
not change with varying deformation percent. At high deformation no extra benefit in maximum
value of hardness could be noted. Most of the alloys show softening during initial period of
annealing and increase in hardness after annealing finally enables the maximum hardness to reach
a magnitude which is comparable to the initial hardness of cold worked alloys. When the alloys
are annealed at higher temperature a sharp decrease in hardness is observed for all the alloys.
Thus appreciable drop in hardness values are noted at annealing temperatures beyond 300o
C.
Figure 5 shows the peak hardness of the alloys at different cold rolled state. It is shown that all
the hardness increases with increasing of the cold rolling. Higher scandium added alloy attended
the higher hardness.
4. Advances in Materials Science and Engineering: An International Journal (MSEJ), Vol. 1, No. 1, September 2014
42
40
50
60
70
80
90
100
0 100 200 300 400 500
Annealing temperature, o
C
Hardness,VHN
Alloy 1
Alloy 2
Alloy 3
Figure 2. Isochronal annealing curve of the 35% cold rolled alloys annealed for 1 hour.
40
50
60
70
80
90
100
0 100 200 300 400 500
Annealing temperature, o
C
Hardness,VHN
Alloy 1
Alloy 2
Alloy 3
Figure 3. Isochronal annealing curve of the 50% cold rolled alloys annealed for 1 hour.
40
50
60
70
80
90
100
0 100 200 300 400 500
Annealing temperature, o
C
Hardness,VHN
Alloy 1
Alloy 2
Alloy 3
Figure 4. Isochronal annealing curve of the 75% cold rolled alloys annealed for 1 hour.
5. Advances in Materials Science and Engineering: An International Journal (MSEJ), Vol. 1, No. 1, September 2014
43
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80
% cold rolling
Hardness,VHN
Alloy 1
Alloy 2
Alloy 3
Figure 5. Variation of hardness of different cold rolled alloys annealed at 300o
C for one hour
Figure 6 shows the electrical resistivity of the alloys at different cold rolled state annealed at
300o
C for one hour. Electrical resistivity decreases with the increase of the cold deformation.
From the resistivity curve the initial resistivity of the scandium added alloys show higher than
base alloy due to grain refining.
5.5
5.7
5.9
6.1
6.3
6.5
6.7
6.9
0 10 20 30 40 50 60 70 80
% cold rolling
Resistivity,micro-Ohm.cm
Alloy 1
Alloy 2
Alloy 3
Figure 6. Variation of electric resistivity of different cold rolled alloys annealed at 300o
C for one hour
3.2. Isothermal Micrographs
3.2.1 Scanning Electron Micrographs
Scanning electron microstructures of the base alloy shows coarse dendrites with high quantity of
second phase constituents. The second phase is found to be contained in the inter-dendritic space
(Figure 7). In 0.6Wt % scandium added alloy 3, not only there happens refinement of dendrites
but also the second phase constituent has been reduced in amount (Figures 8).
6. Advances in Materials Science and Engineering: An International Journal (MSEJ), Vol. 1, No. 1, September 2014
44
Figure 7. SEM micrograph of cast alloy 1.
Figure 8. SEM micrograph of cast alloy 3
3.2.2 Optical Micrographs
The cold worked alloy shows relatively coarse non-uniform grain structure. The overall
appearance is columnar grains with second phase particles remaining aligned along the grain
boundaries. The microstructure of base alloy annealed at 300o
C after 75% cold rolling shows
partially recrystallised grains with ample second phase particles at the grain boundaries (Figure
9). In case of alloy 2 (0.2 wt% Sc) there is no evidence of recrystallisation after annealing at
300o
C (Figure 10). Recrystallisation could not be effected also in alloys 3 after annealing at
300o
C. It may be noted that a circularity of grains is maximum in alloy 2, which contains large
elongated grains. On the contrary higher scandium containing alloy 3 has exhibited elongated
grains of smaller size (Figure 11). If the alloys are annealed at 400o
C, the base alloy is seen to be
recrystallised almost fully (Figure 12). The scandium added alloy 3, on the other hand do not
recrystallise even when annealed at 400o
C (Figure 13). A good number of elongated grains are
present in the microstructure.
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Figure 9. Optical micrograph of 75% cold rolled alloy 1 annealed at 300o
C for one hour.
Figure 10. Optical micrograph of 75% cold rolled alloy 2 annealed at 300o
C for one hour.
Figure 11. Optical micrograph of 75% cold rolled alloy 3 annealed at 300o
C for one hour.
100µµµµm
100µµµµm
100µµµµm
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Figure 12. Optical micrograph of 75% cold rolled alloy 1 annealed at 400o
C for one hour.
Figure 13. Optical micrograph of 75% cold rolled alloy 3 annealed at 400o
C for one hour.
3.2.3 Transmission Electron Micrographs
High resolution micrograph of alloy 2 (Figure 14) showing needles of Al3Sc; strain field around
the needles is visible. The morphology demonstrates that the coherent precipitates of Al3Sc are
needle shaped in their early stage.
Figure 14. High resolution micrograph of alloy 2 showing needles of Al3Sc
50µµµµm
25µµµµm
10nm
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4. DISCUSSION
The initial softening of the cast and cold worked alloys during isochronal annealing is thought be
due to rearrangement of dislocations at the annealing temperature. The precipitation hardening of
the alloys containing scandium is attributable to the formation of Al3Sc precipitates. Higher
scandium added alloys shows higher strength due to higher volume fraction of precipitates. The
strengthening is found to be greater for alloys with higher deformation because a higher degree of
strain hardening resulted from higher dislocation density. But the extent of precipitation
hardening has not improved. This means that extra advantage is not accruable by working
scandium treated alloys. Moreover there has not been any change in the peak hardness
temperature due to cold working. This signifies that scandium precipitation is not dislocation
induced. Moreover extensive cold working also generates large number of vacancies, which form
vacancy-scandium atom complexes of high binding energy. The vacancy-solute atom complexes
reduce the mobility and availability of solute atoms at low temperature to form G P zones. Hence
hardening takes place only at a temperature high enough to decompose the complexes thereby
making solute scandium atoms available for precipitate formation. Beyond peak hardness, over
ageing effect due to coarsening of the precipitates is seen to have taken place. At higher annealing
temperature there is ample scope for dislocation annihilation and this softens the material. The
precipitates formed by trace element hinder dislocation movement and thus limit the softening.
The major drawback of Al-6Mg alloy in respect of undergoing softening during use is overcome
by scandium addition. It is found from hardness plots that pinning of dislocation by formation of
Al3Sc onto them is unlikely. Nevertheless once formed, the precipitates hinder the motion of
dislocations and hence lessen softening [12].
The effect of grain refinement is clearly evident from the resistivity curves, which show a
significant difference of resistivity values of the scandium added alloy with that of the base alloy.
The initial high resistivity of scandium treated alloy is indicative of high electron scattering sites
viz. grain boundary area to mean that grains in all those alloys are finer. Formation of
supersaturated solid solution assures a high precipitation hardening effect upon decomposition of
this solid solution with the formation of fine coherent equilibrium Al3Sc precipitates [12].
From the phase diagram of the alloy it is found that the present alloys would contain α + β
eutectic within the primary dendrites of α. Here ‘α’ is the aluminum rich solid solution and β is
composed of intermetallics, primarily Al8Mg5 along with aluminides of other metals like iron,
chromium, zirconium, manganese, which are present in small quantities in the aluminum used for
the present experimentation. The number of non-equilibrium segregation is dependent on the
magnesium content and the concentration of other potential aluminide formers. However,
scandium forms an anomalous supersaturated solid solution which decomposes to form Al3Sc
[13]. The dendrites of the cast binary alloy are seen to have refined significantly with the addition
of scandium. This is ascribed to the modification of solidification speed by scandium during the
growth of the dendrite structure [14]. Also scandium-containing alloy is seen to have contained
less amount of intermetallic compounds. Due to increase in solidification speed, the super-cooling
effect is weakened. The consequential faster solidification leads to decrement in the amount and
size of the second phase constituents with scandium addition. The faster solidification also aids in
the retention of more solutes in solution. Since dendrites are refined with scandium addition, the
size of individual second phase region becomes smaller as these phases are formed within the
inter-dendritic spaces. Though general observations under optical microscopy have not provided
much information, the overall appearance of the microstructure resembles what are normally
observed in cast aluminum alloy ingot [15]. The cold worked structures are comprised of
elongated grains. When annealed at 300o
C no alloy except base alloy shows the sign of
recrystallisation. The base alloy however has started recrystallising as it is known that
recrystallisation of Al-6Mg alloy becomes completed at about 400o
C. However alloys 2 and 3
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48
have dispersion of fine precipitates of Al3Sc. These precipitates are coherent with the matrix. It is
reported that recrystallisation is almost impossible in aluminum alloys when such particles are
already present [2, 3]. Higher becomes the volume fraction of precipitates higher would be there
crystallisation start temperature. The precipitates hinder the movement of sub-boundaries and
grain boundaries. On increasing the temperature to 400o
C, the second phase constituent is almost
dissolved in base alloy and there is nothing to hinder dislocation movement. As a result
recrystallisation becomes complete. In alloys containing scandium the supersaturated solution
decomposes to formAl3Sc at around 300o
C. These precipitates are known to be resistant to
coarsening. There are reports saying that increasing the annealing temperature of Al-Mg-Sc alloy
from 300o
C to 400o
C increases the size of Al3Sc precipitates from 4 nm to 13 nm. The
precipitates of Al3Sc remain coherent with the matrix even when their size increases to 100 nm
due to higher temperature of annealing [1]. In the present case however the precipitate size is
around 15 nm when annealed at 400o
C. Therefore dislocation pinning force is very large. As a
result recrystallisation is not possible.
High resolution micrograph shows the presence of fine needles of 10 nm size surrounded by
strain field (Figure 14). These are supposed to be Al3Sc precipitates which are known to form in
aluminium alloys containing scandium. The morphology demonstrates that the coherent
precipitates of Al3Sc are needle shaped in their early stage. In base alloy the monoclinic phases
are likely to exhibit specific habit of ά being parallel to {110} planes. This causes difficulty for
slipping along <110> direction of the fcc matrix. Hence critical resolved shear stress apparently
increases and nucleation of micro twins becomes inevitable [16].
5. CONCLUSIONS
The scandium added alloys show the precipitation hardening behavior during annealing. It is
attributable to the formation of Al3Sc precipitates. The initial softening is thought to be due to the
recovery in the cold worked alloys. The strengthening is found to be greater for alloys with higher
deformation because a higher degree of strain hardening resulted from higher dislocation density.
The trace element precipitates of Al3Sc hinder dislocation movement and thus limit the softening.
During the cold deformation, electrical conductivity decreases due to the increase of the number
of vacancies and the density of dislocations. The microstructure shows that dendrites of the cast
base alloy are refined significantly with the addition of scandium. The addition of scandium
severely retards the recrystallization of the alloys when it is present in the form of fine Al3Sc
precipitates.
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Author
Dr. Md. Salim Kaiser was born in Jhenaidah, Bangladesh on November 01, 1962. He
received his Graduation degree in Mechanical Engineering from Institution of Engineers,
Bangladesh, in 1990, PGD in Industrial Management from Bangladesh Management
Development Center, Dhaka, in 1992, the M. Engg. degree in optics from BIT Khulna,
Bangladesh, in 2000 and the Ph.D. degree in Material science from Bengal Engineering
and Science University, Shibpur, India, in 2005. He also worked as a post doctoral
fellow, School of Materials Science & Engineering of Bengal Engineering and Science University in 2012.
His research interests include Materials Science Engineering, Physics and Astronomy. At present, he is
working as Deputy Director, Directorate of Advisory, Extension and Research Services, Bangladesh
University of Engineering and Technology, Dhaka. Dr. Kaiser is a fellow of Engineers Institution
Bangladesh (IEB) and Bangladesh Computer Society (BCS).