This document discusses grain refiners and modifiers used in aluminum casting. It provides details on:
- The behavior of grain refiners over time, including initial rapid grain size reduction, achievement of ultimate grain size, and potential subsequent grain growth known as "fade".
- How various elements like titanium, zirconium, and vanadium can affect grain refiners through competitive absorption and formation of stable surface layers on refining particles.
- The roles of sodium and strontium in modifying eutectic silicon morphology in aluminum-silicon alloys, and how strontium provides more consistent modification with less fade.
- Factors that influence grain refinement effectiveness such as refiner type, addition
Computer Science
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Broadband wireless technologies
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Communication architectures for pervasive computing
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Computer and microprocessor-based control
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Computer-based information systems in health care
Computing Ethics
Computing Practices & Applications
Congestion and/or Flow Control
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Context-awareness and middleware
Creativity in Internet management and retailing
Cross-layer design and Physical layer based issue
Cryptography
Data Base Management
Data fusion
Data Mining
Data retrieval
Data Storage Management
Decision analysis methods
Decision making
Digital Economy and Digital Divide
Digital signal processing theory
Distributed Sensor Networks
Drives automation
Drug Design,
Drug Development
DSP implementation
E-Business
E-Commerce
E-Government
Electronic transceiver device for Retail Marketing Industries
Electronics Engineering,
Embeded Computer System
Emerging advances in business and its applications
Emerging signal processing areas
Enabling technologies for pervasive systems
Energy-efficient and green pervasive computing
Environmental Engineering,
Estimation and identification techniques
Evaluation techniques for middleware solutions
Event-based, publish/subscribe, and message-oriented middleware
Evolutionary computing and intelligent systems
Expert approaches
Facilities planning and management
Flexible manufacturing systems
Formal methods and tools for designing
Fuzzy algorithms
Fuzzy logics
GPS and location-based app
experimental studies on high performance concrete using metakaolinIjripublishers Ijri
In this present experimental investigation an attempt is made to the strength and behavior of the meta kaolin, super
plasticiser and other chemicals on high performance concrete. Cement is replaced by 0%, 20% of Metakaolin by volume
of concrete, thus resulting in the increase in strength. Super-plasticizer is used to increase the workability of concrete,
increase the density and strength. It can permit the reduction in the water cement ratio up to 15%,.Dosage of superplasticizer
is 1.5% by weight of cement.
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
Computer Science
Active and Programmable Networks
Active safety systems
Ad Hoc & Sensor Network
Ad hoc networks for pervasive communications
Adaptive, autonomic and context-aware computing
Advance Computing technology and their application
Advanced Computing Architectures and New Programming Models
Advanced control and measurement
Aeronautical Engineering,
Agent-based middleware
Alert applications
Automotive, marine and aero-space control and all other control applications
Autonomic and self-managing middleware
Autonomous vehicle
Biochemistry
Bioinformatics
BioTechnology(Chemistry, Mathematics, Statistics, Geology)
Broadband and intelligent networks
Broadband wireless technologies
CAD/CAM/CAT/CIM
Call admission and flow/congestion control
Capacity planning and dimensioning
Changing Access to Patient Information
Channel capacity modelling and analysis
Civil Engineering,
Cloud Computing and Applications
Collaborative applications
Communication application
Communication architectures for pervasive computing
Communication systems
Computational intelligence
Computer and microprocessor-based control
Computer Architecture and Embedded Systems
Computer Business
Computer Sciences and Applications
Computer Vision
Computer-based information systems in health care
Computing Ethics
Computing Practices & Applications
Congestion and/or Flow Control
Content Distribution
Context-awareness and middleware
Creativity in Internet management and retailing
Cross-layer design and Physical layer based issue
Cryptography
Data Base Management
Data fusion
Data Mining
Data retrieval
Data Storage Management
Decision analysis methods
Decision making
Digital Economy and Digital Divide
Digital signal processing theory
Distributed Sensor Networks
Drives automation
Drug Design,
Drug Development
DSP implementation
E-Business
E-Commerce
E-Government
Electronic transceiver device for Retail Marketing Industries
Electronics Engineering,
Embeded Computer System
Emerging advances in business and its applications
Emerging signal processing areas
Enabling technologies for pervasive systems
Energy-efficient and green pervasive computing
Environmental Engineering,
Estimation and identification techniques
Evaluation techniques for middleware solutions
Event-based, publish/subscribe, and message-oriented middleware
Evolutionary computing and intelligent systems
Expert approaches
Facilities planning and management
Flexible manufacturing systems
Formal methods and tools for designing
Fuzzy algorithms
Fuzzy logics
GPS and location-based app
experimental studies on high performance concrete using metakaolinIjripublishers Ijri
In this present experimental investigation an attempt is made to the strength and behavior of the meta kaolin, super
plasticiser and other chemicals on high performance concrete. Cement is replaced by 0%, 20% of Metakaolin by volume
of concrete, thus resulting in the increase in strength. Super-plasticizer is used to increase the workability of concrete,
increase the density and strength. It can permit the reduction in the water cement ratio up to 15%,.Dosage of superplasticizer
is 1.5% by weight of cement.
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
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.
An Experimental Investigation on Strength Characteristics of Concrete with P...IJMER
One of the approaches in improving the durability of concrete is to use blended cement
materials such as fly ash, silica fume, slag and more recently, metakaolin.. This study presents the results
of different mechanical properties of concrete such as compressive strength, split tensile strength and
flexural concrete by partially replacing cement with metakaolin and silica fume. The replacement of
metakaolin is varied from 10%, 15%, 20% and 25% and silica fume from 6%, 8% and 10%. The property
of concrete in fresh state, that is the workability is also studied during the present investigation.The
optimum doses of silica fume and metakaolin in combination were found to be 6% and 15% (by weight)
respectively, when used as part replacement of ordinary Portland cement.
Strength Studies on Metakaolin Modified Cement Mortar with Quarry Dust as Fin...IDES Editor
Scarcity of river sand is one of the major problems
in the construction industry. Studies were conducted to find
out the feasibility of using quarry dust to partially replace
sand in concrete. . These studies revealed that, due to increased
fineness, the combination require an increased water cement
ratio which results in strength reduction or the use of a water
reducing admixture. Use of super pozzolanic supplementary
cementing materials such as silica fume, rice husk ash,
metakaolin etc in concrete and mortar improves the strength
even at a higher water binder ratio. Metakaolin, a
manufactured material, calcined kaolinite is available at
moderate cost. This paper presents the results of a study to
use metakaolin in cement mortar as a partial replacement of
cement where quarry dust was used as the fine aggregate.
The effect of water binder ratio and metakaolin replacement
level on the compressive strength of cement quarry dust mortar
was investigated.
Punching Shear Strength of High Strength Fibre Reinforced Concrete SlabsIJMER
The experimental study of punching shear behavior of High Strength fiber reinforced
concrete slabs is carried out in the present work. Each of 24 square slabs was simply supported along
four edges and loaded to failure under a concentrated load over a square area at the center. The test
parameters were the effective span to depth aid ratio, volume fraction of 3 types of steel fibers, slab
thickness h, concrete strength fck, and size of load-bearing plate r. Test results indicate that the load
Evaluation of Self Consolidating Steel Fibre Concrete (SCSFRC) & Its Fresh Pr...IOSR Journals
Superior performances of Self-Compacting Concrete (SCC) in fresh state to achieve a more uniform distribution encourage the addition of fibers in concrete which is a motivation for structural application of fibre reinforced concrete. Steel fibre used in the Self Consolidating Steel Fibre concrete (SCSFRC) is to enrich the performance of the concrete material. But SCC has intrinsic low ductility and poor toughness which restrict the fields of application of SCC. The disadvantage of SCC can be avoided by reinforcing with randomly distributed discontinuous fibers. Traditionally rational mix design method is available for SCC which make tedious to obtain the self compacting properties in various mix proportion of concrete. The mix design is based on principle of limiting range for total aggregate volume and coarse aggregate volume in concrete. It forms the basis for the concrete to be flowable and to achieve high workability. This paper focus on the design mix for SCSFRC, mix design principle and experimental investigation carried out on Self Consolidating Steel Fibre Reinforced Concrete (SCSFRC) fresh properties
UTILIZATION OF COPPER SLAG AS A PARTIAL REPLACEMENT OF FINE AGGREGATE IN CONC...AM Publications
Today’s world is facing challenging and unsolved environmental problem such as global warming, forest destruction and lack of resources. In order to solve these environmental problems, resources recycling have to be done in environmentally safer methods. As there is a vast scarcity the production of aggregates for concrete the recycled materials have great demand. The present study mainly focuses on investigating the effect of using copper slag as a replacement of fine aggregate on the strength properties. In this report, M25 grade concrete was used and tests were conducted for various proportions of copper slag replacement with sand of 40%, 80% and 100% in concrete. In the first case along with replacement of copper slag with sand there is an attempt is made to replace the cement with 50% flyash similarly in second case for 30% replacement of cement with flyash replacement and in the third case with no replacement of cement with flyash. The obtained results were compared with those of nominal concrete made with ordinary Portland cement and sand. Further split tensile strength and flexural strength studies were also performed to check its durability aspects.
- In the present scenario carbon emission and sand
mining are major concern due to its hazardous effect to
environment and making serious imbalance to the ecosystem.
Various studies have been conducted to reduce severe effect on
environment, using byproducts like copper slag as partial
replacement of fine aggregate. Different researchers have also
revealed numerous uses of copper slag as a replacing agent in
determining the strength of concrete. A comprehensive review of
studies has been presented in this paper for scope of replacement
of fine aggregate from copper slag in concrete
This paper presents part of the results of an ongoing laboratory study carried out to study on
strength and durability characteristics of ternary concrete made with and without ternary mixtures of
cement-fly ash- silica fume. In the present work an attempt has been made to study the strength
properties of ternary concrete in compression, tension and flexure and also durability aspects of
ternary blended concrete. In the investigation, M25 Grade concrete mix is designed with different
percentages of cementitious materials (5%, 7.5%, 10% & 12.5%) and tests are conducted for
compressive strength, split tensile strength and flexure strengths at 7, 28 and 56 days. Test results
indicate that the replacement of cement by 10% had attained a maximum strength in M25 Grade
concrete. The results obtained thus are encouraging for partial replacement.
Melt treatment of aluminum alloys are typically carried out in transfer furnaces prior to casting.
Depending on the size of the crucible and the volume of the castings, the melt may be led to remain in the liquid
state up to two hours. It is well known that as the holding period is increased, the effect of modifiers fade away.
In this work, the mechanism of this fading effect has been investigated for the first time by means of melt
cleanliness. Reduced pressure test was used to measure bifilm index of the melt. Al-19Si was used and two
temperatures were selected: 725oC and 800oC. Hydrogen content of the melt was measured by AlSPEK and
excess amount of Al-15Sr modifier was added once the desired temperature was reached. Samples were
collected every 20 minutes up to two hours and the microstructural results (i.e. efficiency of modification) was
correlated with bifilm index (melt quality).
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.
An Experimental Investigation on Strength Characteristics of Concrete with P...IJMER
One of the approaches in improving the durability of concrete is to use blended cement
materials such as fly ash, silica fume, slag and more recently, metakaolin.. This study presents the results
of different mechanical properties of concrete such as compressive strength, split tensile strength and
flexural concrete by partially replacing cement with metakaolin and silica fume. The replacement of
metakaolin is varied from 10%, 15%, 20% and 25% and silica fume from 6%, 8% and 10%. The property
of concrete in fresh state, that is the workability is also studied during the present investigation.The
optimum doses of silica fume and metakaolin in combination were found to be 6% and 15% (by weight)
respectively, when used as part replacement of ordinary Portland cement.
Strength Studies on Metakaolin Modified Cement Mortar with Quarry Dust as Fin...IDES Editor
Scarcity of river sand is one of the major problems
in the construction industry. Studies were conducted to find
out the feasibility of using quarry dust to partially replace
sand in concrete. . These studies revealed that, due to increased
fineness, the combination require an increased water cement
ratio which results in strength reduction or the use of a water
reducing admixture. Use of super pozzolanic supplementary
cementing materials such as silica fume, rice husk ash,
metakaolin etc in concrete and mortar improves the strength
even at a higher water binder ratio. Metakaolin, a
manufactured material, calcined kaolinite is available at
moderate cost. This paper presents the results of a study to
use metakaolin in cement mortar as a partial replacement of
cement where quarry dust was used as the fine aggregate.
The effect of water binder ratio and metakaolin replacement
level on the compressive strength of cement quarry dust mortar
was investigated.
Punching Shear Strength of High Strength Fibre Reinforced Concrete SlabsIJMER
The experimental study of punching shear behavior of High Strength fiber reinforced
concrete slabs is carried out in the present work. Each of 24 square slabs was simply supported along
four edges and loaded to failure under a concentrated load over a square area at the center. The test
parameters were the effective span to depth aid ratio, volume fraction of 3 types of steel fibers, slab
thickness h, concrete strength fck, and size of load-bearing plate r. Test results indicate that the load
Evaluation of Self Consolidating Steel Fibre Concrete (SCSFRC) & Its Fresh Pr...IOSR Journals
Superior performances of Self-Compacting Concrete (SCC) in fresh state to achieve a more uniform distribution encourage the addition of fibers in concrete which is a motivation for structural application of fibre reinforced concrete. Steel fibre used in the Self Consolidating Steel Fibre concrete (SCSFRC) is to enrich the performance of the concrete material. But SCC has intrinsic low ductility and poor toughness which restrict the fields of application of SCC. The disadvantage of SCC can be avoided by reinforcing with randomly distributed discontinuous fibers. Traditionally rational mix design method is available for SCC which make tedious to obtain the self compacting properties in various mix proportion of concrete. The mix design is based on principle of limiting range for total aggregate volume and coarse aggregate volume in concrete. It forms the basis for the concrete to be flowable and to achieve high workability. This paper focus on the design mix for SCSFRC, mix design principle and experimental investigation carried out on Self Consolidating Steel Fibre Reinforced Concrete (SCSFRC) fresh properties
UTILIZATION OF COPPER SLAG AS A PARTIAL REPLACEMENT OF FINE AGGREGATE IN CONC...AM Publications
Today’s world is facing challenging and unsolved environmental problem such as global warming, forest destruction and lack of resources. In order to solve these environmental problems, resources recycling have to be done in environmentally safer methods. As there is a vast scarcity the production of aggregates for concrete the recycled materials have great demand. The present study mainly focuses on investigating the effect of using copper slag as a replacement of fine aggregate on the strength properties. In this report, M25 grade concrete was used and tests were conducted for various proportions of copper slag replacement with sand of 40%, 80% and 100% in concrete. In the first case along with replacement of copper slag with sand there is an attempt is made to replace the cement with 50% flyash similarly in second case for 30% replacement of cement with flyash replacement and in the third case with no replacement of cement with flyash. The obtained results were compared with those of nominal concrete made with ordinary Portland cement and sand. Further split tensile strength and flexural strength studies were also performed to check its durability aspects.
- In the present scenario carbon emission and sand
mining are major concern due to its hazardous effect to
environment and making serious imbalance to the ecosystem.
Various studies have been conducted to reduce severe effect on
environment, using byproducts like copper slag as partial
replacement of fine aggregate. Different researchers have also
revealed numerous uses of copper slag as a replacing agent in
determining the strength of concrete. A comprehensive review of
studies has been presented in this paper for scope of replacement
of fine aggregate from copper slag in concrete
This paper presents part of the results of an ongoing laboratory study carried out to study on
strength and durability characteristics of ternary concrete made with and without ternary mixtures of
cement-fly ash- silica fume. In the present work an attempt has been made to study the strength
properties of ternary concrete in compression, tension and flexure and also durability aspects of
ternary blended concrete. In the investigation, M25 Grade concrete mix is designed with different
percentages of cementitious materials (5%, 7.5%, 10% & 12.5%) and tests are conducted for
compressive strength, split tensile strength and flexure strengths at 7, 28 and 56 days. Test results
indicate that the replacement of cement by 10% had attained a maximum strength in M25 Grade
concrete. The results obtained thus are encouraging for partial replacement.
Melt treatment of aluminum alloys are typically carried out in transfer furnaces prior to casting.
Depending on the size of the crucible and the volume of the castings, the melt may be led to remain in the liquid
state up to two hours. It is well known that as the holding period is increased, the effect of modifiers fade away.
In this work, the mechanism of this fading effect has been investigated for the first time by means of melt
cleanliness. Reduced pressure test was used to measure bifilm index of the melt. Al-19Si was used and two
temperatures were selected: 725oC and 800oC. Hydrogen content of the melt was measured by AlSPEK and
excess amount of Al-15Sr modifier was added once the desired temperature was reached. Samples were
collected every 20 minutes up to two hours and the microstructural results (i.e. efficiency of modification) was
correlated with bifilm index (melt quality).
Aluminum-lithium alloys used in the aerospace industry as structural components
and strengthened by age-hardening. This study aims to improve properties of Al-Li
alloys such as strength, behavior hot rolling and addition element, i.e. Mg and Cu to
this alloy. Several tests were carried out to evaluate the performance of alloy, such as
hardness, tensile, and microstructure by OP, SEM and XRD. Result showed that
addition 3.2% Cu to base alloy improve strength from (62MPa) to (78MPa) when
aging at 175°C.and improve hardness from (97.3 Hv) to (119.79Hv) At the same
temperature. But the improvement is great when addition 0.6% Mg to base alloy
improve tensile strength from (62MPa) to (124MPa) at the same time improved
hardness from (119.79Hv) to (152.96Hv) at the same temperature.
Microstructure and Process Annealing of Steels.pptxMANICKAVASAHAM G
Process annealing is performed to improve the cold-working properties of low-carbon steels (up to 0.25% carbon) or to soften high-carbon and alloy steels to facilitate shearing, turning or straightening processes. Process annealing involves heating the steel to a temperature below (typically 10–20°C below) the lower critical temperature (Ac1) and is often known as ‘subcritical’ annealing.
After heating, the steel is cooled to room temperature in still air.
The process annealing temperatures for plain carbon and low alloy steels is typically limited to about 700°C to prevent partial reaustenitisation.
In some cases this is limited to about 680°C for steel compositions, such as high-nickel containing steels, where the nickel further reduces the Ac1 temperature[Ref. .31].
This process can be used to temper martensitic and bainitic microstructures to produce a softened microstructure containing spheroidal carbides in ferrite[Ref. 31].
Fine pearlite is also relatively easily softened by process annealing, while coarse pearlite is too stable to be softened by this process.
Annealing of Steels
When a metal is cold worked (deformed at room temperature), the microstructure becomes severely distorted because of an increased dislocation density resulting from the deformation.
Cold working is also referred to as work hardening or strain hardening.
As a metal is cold worked, the strength and hardness increase while ductility decreases.
Grain growth
It is the growth of some recrystallized grains, and it can only happen at the expense of other recrystallized grains.
Because fine grain size leads to the best combination of strength and ductility, in almost all cases, grain growth is an undesirable process.
Although excessive grain growth can occur by holding the material for too long at the annealing temperature, it is normally a result of heating at too high a temperature.
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.
Aluminium Matrix Composites (AMC’s) are widely used in aerospace, automotive,
structural and marine applications due to their high strength to weight ratio, corrosion
resistance. In AMC one of constituent is aluminium or its alloy which forms a network
called as matrix phase and other constituent is embedded in matrix made of harder material
generally ceramic or non metallic material called as reinforcement. Various processing
techniques are available for manufacturing of AMC’s. Stir casting is one of the economical
and extensively used methods to enhance attractive properties of AMC’s. This paper
presents an overview of stir casing process, process parameter and preparation of AMC
using aluminium alloy as matrix phase and alumina (Al2O3) as reinforcement by varying
their proportion.
Recent growth of construction
industry has increased the demand of cement.
Increase of the cement utilization demands for
higher production efficiency and ultimately low
production cost. The efficiency of the cement
production depends greatly upon the efficiency of
a grinding mill which consumes 60-70% of the
total electricity consumption of the cement
plant[12]. A grinding mill (Ball Mill) is used to
grind the cement clinker into fine cement powder.
Grinding Aids are used to improve the grinding
efficiency and reduce power consumption. This
paper discusses the grinding aids mechanism and
improvement in grinding efficiency due to various
grinding aids viz .polyols, amines . This paper also
focus on the effects of grinding aids on the
mechanical properties of cement such as setting
time, specific surface, compressive strength at various ages.
Microstructure and Hardness of Aluminium Alloy- Fused Silica Particulate Comp...AM Publications
Aluminum matrix composites (AMCs) refer to the class of light weight high performance aluminum centric
material systems. The reinforcement in AMCs could be in the form of continuous/discontinuous fibers, whiskers or particulates,
in volume fractions. Properties of AMCs can be tailored to the demands of different industrial applications by suitable
combinations of matrix, reinforcement and processing route. This work focuses on the fabrication of aluminum alloy (LM13)
matrix composites reinforced with 9%, 12% &15% fused silica particulates using stir casting route. The microstructure and
hardness of the fabricated composite were analyzed and reported.
TRIBOLOGICAL CHARACTERISTICS OF ALUMINIUM HYBRID COMPOSITES REINFORCED WITH S...Blaza Stojanovic
This paper presents tribological characteristics of hybrid composites with aluminium
matrix, reinforced with silicon carbide (SiC) and graphite (Gr). Newly
formed Al/SiC/Gr hybrid composites are the combination of the two different hybrid
materials. Namely, hard particles of silicon carbide increase the hardness and
resistance to wear, while soft particles of graphite improve lubrication and reduce
friction coefficient and wear. It is possible to obtain Al/SiC/Gr hybrid composites
by different methods of casting. Tribological tests show that load, sliding speed,
sliding distance, content and size of reinforcement particles influence the size
and the type of wear and friction coefficient of Al/SiC/Gr hybrid composites with
aluminium matrix.
TRIBOLOGICAL CHARACTERISTICS OF ALUMINIUM HYBRID COMPOSITES REINFORCED WITH S...
Technology0614
1. Technology
June 201436
- AMIT KAMBLE, Manager R&D, Minex Metallurgical Co. Ltd.
Grain Refiners
& Modifiers for the
Aluminum Foundry
2. June 201437
Behaviour of Grain Refiner
ContactTimeandFade
Fig.1 shows the grain size vs. time curve
after grain refiner addition. The curve is
characterized by initial rapid decline in grain
size to ultimate grain size (UGS) at contact
time tc, followed by a rise in gain size at longer
times. This loss of refinement is termed as
'fade'. Fade can be ameliorated in part by
stirring the melt, through the degree of recover
depends on the melt compositions [6]. It is
known that grain refinement can be lost if a
melt is held above 750°C, but that this can be
regained if more titanium is added and melt is
stirred.
Fig.1 : Schematic form of grain size vs. log time
behaviour following addition of grain refiner to
Al alloy melt [6]
Fig. 2 : Schematic representation of dilute Al-Ti
phase diagram showing liquidus for TiAl3 on TiB2.
Sequence A to B to c shows how potency may be
lost and regained [6]
EffectofRefiningParticles
Following the rod addition, TiAl3
particles dissolves rapidly (40µm/min) and
with good stirring 90% Ti will be in solution
within 10s for a typical distribution of
aluminum sizes. Depending on the melt
temperature and composition, the TiAl3
overlayers on TiB2 may grow slightly, remain
stable, desorbs or undergo site competitive
substitution with other transition metal
elements present in the alloy melt. Fig.2 (Fig.3)
demonstrates how the absorbed TiAl3 layer
may be lost and reformed. Substitution and site
competition effects may be estimated from
dilute Al-X binary phase diagrams which are
shown super imposed in Fig.4 from this fig. it is
possible to see Zr and V compete strongly with
Ti at particularly lower temperatures and that
Ta will form a stable layer. Whilst aluminide
dissolution and TiB2 interfacial chemistry
changes are in progress, some degree of
particle collision, sticking and settling will
occur. If holding times are long then there will
be fewer particles remaining in the melt to
nucleate grains. It will also be likely that those
remaining in the suspension will be smaller on
average than immediately after addition as
largerparticlessettlefirst.
Fig. 3 : Schematic representation of processes
occurring on addition of TiBAl grain refiner to
aluminum melt showing how the characteristic
form of behavior emerges [6]
Solidification
Fig. 4 : Dilute portions of Al-Ti, Al-Zr, Al-V and Al-Ta
phase diagrams showing relative stabilities of
aluminides which affects preferred adsorption
behavior on TiB2 [6]
Grain refinement can be understood to be
directly related to the nucleation and growth
process of aluminum grains. This is based on
Volmer and Weber ideas for homogeneous and
heterogeneous nucleation [10]. Fig. 5 shows
the solid nucleating on the substrate on liquid.
The critical free energy for heterogeneous
nucleation is always less than or equal to that
for homogenous nucleation. The values of
undercooling, ? T is of order of 1 – 2 K for
observable nucleation rates in commercial
aluminum alloy with grain refiners. Therefore
clearly heterogeneous nucleation is taking
place. The expression for heterogeneous
nucleation rate per unit volume in m-3s-1 is by
equation(1).
Fig. 5 : Schematic representation showing the
formation of spherical cap of solid (s) on a
Fig. 6 : Schematic distribution of undercoolings
required substrate, contact angle and surface
tension by different nuclei within a grain refined
melt. [6] forces [10]
Under the heat flow conditions prevailing
during solidification, the melt becomes
undercooled until sufficient undercooling is
achieved for particles to nucleate á-Al by the
peritectic reaction (Fig. 6). In order to achieve
finest grain size, it will be necessary to activate
the median portion of the undercooling
3. June 201438
distribution. In reality undercooling will vary
from positions to positions because of local
heatflow and constitutionaleffects.
Behaviour of Grain Modifier & its
Selection for Al Casting
Comparison of Sodium & Strontium
Modifier
Modifiers are added to eutectic and hyper
eutectic Al-Si alloys to refine the eutectic Si
phase from one of angular platelets to fine
fibers. This change in microstructure results in
improved mechanical properties, particularly
strength and ductility [01]. Modification also
leads to refined porosity which leads to an
additional improvement in mechanical
properties.
The first hypoeutectic modifiers were
based on Na, and are added as Na metal or
encapsulated Na in Al foil. Due to high
reactivity and low solubility of Na in
aluminum (recoveries low up to ~ 20%) with
gradual loss of Na with time (fade) results in a
process thatisdifficulttocontrol.
In sodium modified melt the eutectic
growth front is typically planer, thus allowing
regular solidification through the dendritic
network and minimal entrapment of liquid
pockets [14]. With Sr modification however,
the growth front is more irregular, allowing the
possibility of liquid areas becoming trapped
leading to shrinkage microporosity. The
modifying action of Na practically disappears
after only few remelts. On the other hand, the
modifying effect of strontium does not fade on
holdingatelevatedtemperature[11].
However, longer holding time is required
at 750 C due to the difficulty in dissolution of
strontium, resulting in increased gas pickup.
Finally, although antimony has no fading effect
and the improvement in elongation and impact
strength is greater than that achieved by
sodium, its use has been precluded in most
countries because of environmental and safety
reasons. Thermal modification involves heat-
treatment of cast alloys at high temperature;
usually at the solid solution temperature
around 540 C for long times [12]. Solution heat
treatment results in a substantial degree of
spheroidizationof secondphaseparticles.
Variation of Silicon particles
morphology with modification [15]
In unmodified alloy, the silicon grows as
plates that can be lamellar or acicular. Lamellar
structures are nearly parallel and thin plates,
while acicular structures are randomly
distributed plates with much massive structure.
At an unmodified condition, thin silicon plates
Recovery
Contact Time
Fade
Environmental
Overmodification
Potency
Addition Level (Typical)
Sodium Metal
Low, Variable & Operator Dependent
Immediate
Fast (20-40 min)
Fumes and Refractory Attack
Possible Due to Difficulty of Control
Very High
50 ppm
Al-Sr Alloy
High and Consistent
Up to 10-20 min.
Slow (> 2 hours)
Clean and fume free
Unlikely
High
250 ppm
Unreactive with Moisture if
<20% Strontium Master Alloy
Ease of Handling Must be Protected from Moisture
TABLE 1 : COMPARISON OF SODIUM & STRONTIUM MODIFIER [11]
can be seen cutting through the aluminum
matrix(Fig.7).
Partially modified structures are the
coexistence of flake and fibrous silicon mixed,
cellular or banded structure. They can be
obtained by a combination of slow
solidification rates (bet. 1 & 25µm/s) and low
strontium concentration. At low strontium
concentration and during slow growth, the
eutectic is able to reject enough strontium
ahead its interface to avoid transforming to
fibrous morphology(Fig.8).
In well modified structure silicon grows in
a coral-like form (fibrous) that looks like small
individual round-shaped particles in polished
surface. The modification treatment affects not
only size and shape of the particle, but also its
distribution. Ideal concentration of strontium
results in a fibrous eutectic structure, well
refinedandhomogenous(Fig.9).
When the addition of strontium exceeds
the amount necessary to produce a fully
modified structure, it exerts a deleterious effect
on the mechanical properties of the alloy.
Strontium overmiodification is much more
subtle and difficult to identify by
microstructuralanalysis.
In overmodified alloys, elongated silicon
particles that no longer grow as well as refined
fibers can be observed. However the formation
of Sr-rich phase is reported in strontium
concentration above 0.03% and the eutectic
silicon grows in coarser fibrous form.
Although the morphologies of a well modified
alloy and an overmodified alloy are mostly
coral-like ones, their thickness are
considerablydifferent(Fig.10).
Fig. 7 : Unmodified Alloy (0.0003% Sr) Lamellar
Structure (a) 200X (b) 1500X
Fig. 8 : Partially Modified Structure (Mixed)
(0.0026% Sr) (a) 200X (b) SEM Deep Etched 1500X
Fig. 9 : Fully Modified Structure (0.0075% Sr)
(a) 200x (b) SEM Deep Etched 1000x
Fig.10 : Over Modified Structure (0.0130% Sr)
(a) 200x (b) SEM Deep Etched 1000x
Effect Of Strontium on Reliability Of
Castings
The average mechanical property results
after the various treatments are shown in Fig.
12 these show that the melt treatments lead to
improved mechanical properties in GDCA319
alloy. The addition of modifier gives an
increase in UTS and elongation values,
treatments have resulted in reduction in scatter
as evidenced by an increases in Weibull
modulus from 5.9 (untreated) to 17.6
(modified) [05]. Similarly the Fig.11 shows an
increased fracture toughness value for Sr-
modified alloy A357 compared to unmodified
alloy.
Selection of Grain Refiners
Grain refiners are added to Al-Alloy to
improve the melt processability and to reduce
the size of primary Al grains. These grain
Technology
4. June 201439
Fig.11 : Fracture Toughness of Alloy A357(al-
7si-0.5mg) with and without Sr Modification [14]
Fig.12 : Effect of Melt Treatment on Weibull Plots
of UTS of Gravity Die Castings A319 [05]
refiners can be in various forms. The most
suitable form is master alloys as AlTiB and
AlTiC, it contains TiAl3 particles and TiB2
particle which are responsible for grain
refinement as discussed earlier. Originally
these particles were created into the melt by
addition of compacted powder tablets i.e.
compacted mixture of K2TiF6 and KBF4 salts.
The tablets works as simple dissolution and
reaction of titanium boron tablets or by
dissolution and reaction of titanium and boron
salts in titanium boron tablets as indicated
below.
Because these reactions have to occur in
the melt to form TiB2 nuclei, this addition
method is not as quick or as controllable as
TiBAl master alloy approach, as comparison
shown below:
TABLE 2 : COMPARISON OF TIBAL & SALT
TABLET AS GRAIN REFINER IN FOUNDRY [5]
TiBAl Rod Salt Tablets
Recovery High and
Consistent
Variable and
Operator
Dependent
Contact Time Short (30 sec.) Long (5-10 min)
Efficiency High Low
To be Cont..
Fade 2-4 hours 1-1.5 hours
Dissolution Fast (<30 sec.) Slow (2-5 min.)
Addition
Clean and Fume
Free
Fumes and Flux
Residues
Cost
Comparison
High Low
Industrial Application of TiCAl &
TiBAl
TiCAl refiners (Al-3Ti-0.15C) have been
used industrially in aerospace plate (AA7xxx),
bright trim (AA5xxx), lithographic (AA1xxx),
canstock (AA5xxx) and foil (AA8xxx) alloy
applications. Operationally, the higher
sensitivity of TiCAl to temperature makes it
more suitable for slowly cooled products e.g.
large rolling slabs where the undercooling
driving grain growth is primary [08]. TiCAl
offers advantages in alloy containing Zr, Cr
which can otherwise poison TiBAl refiners. At
a given addition rate and low temperature
TiCAl master alloy is as efficient as TiBAl
alloys in grain refining AA6063. In terms of
quantity of particles added however, both
TiCAl andAl5Ti-0.2B are more potent thanAl-
3Ti-1B. TiBAl is used for strip cast application
with addition rate of 0.15 to 0.4 wt% of grain
refiner. [03]. Recycling test demonstrates that
TiBAl is more robust than TiCAl during the
thermal cycling of AA3004 at 800°C [02].
TiBAl andTiCAl bearing 3xxx and 5xxx alloys
can be recycled effectively with modest
additionofTiBAlafterexposureto800°C.
Comparison of Grain Refiners TiCAl
and TiBAl
It has been estimated typically only 1 in
500 TiB2 particles nucleates grain. Fig. 13
shows relation between no. of particles
required per grain and grain refiner addition
rate for AA1050 at different temp. In general,
with fewer particles present, the nucleation
efficiency of each particle becomes greater.
The loss of potency displayed by TiCAl at
higher temp. may be caused by poisoning.
Conversion of the surface of TiC particles to
Ti2AlC or Al4C3 would destroy the excellent
lattice matching between TiC and á-Al which
is basis of TiC's effectiveness as a nucleant for
aluminum[09].
Thermal cooling dominates at the edges of
castings and constitutional undercooling is
greatest at the centre of cast sections. AlTiB
produces finer grain sizes at billet edges and
therefore responds better to thermal
undercooling (Fig.14). The nuclei generated
near the mould walls will be relatively mobile
and rejected solutes will tend to be dispersed
leading to relatively low constitutional
undercoling. Under such condition most potent
Fig.13 : No of Particles (Calculated) Needed to
Nucleate A Grain in Aa1050 as a Function of
Refiner Type, Addition Rate and Temperature
(a) 670°c (b) 700°c [09]
nucleant will dominate solidification behavior
and so TiB2/TiAl3 produces finer grains at the
mouldwalls.
Fig. 14 Schematic of the constitutionally-
Conversely at billet centre, thermal gradient
supercooled region ahead of the solidification
will be low and the constitutionally-front
showing different behaviour of AlTiC and
AlTiB [10] supercooled zone will be large. The
zone of activation of TiB2 nucleants will be
larger than that for TiC and the opportunity for
nucleation well in advance of growth front will
be greater for TiBAl [09]. The relatively fine
grain size at billet centre is obtained with
TiCAl is therefore suggested to be due to
combination of its greater constitutional
supercooling to become active and its tighter
particle size distribution. ForTiCAl there is no
change observed in grain size with increasing
5. June 201440
mould temperature in the range 25500°C.
Whereas, TiBAl showed coarsening of grain
with rising mould temperature. Thus TiCAl is
more effective in situations where thermal
gradientarelow.
PoisoningEffect
Influence of Zr/Cr on Grain Refiners
Zirconium has a poisoning effect
(especially inTiBAl, not inTiCAl) on the grain
refiner efficiency more obvious at higher
melting temperature. G.P. Jones and J. Pearson
suggest that the fading mechanism is mainly
due to the formation of a thin layer of ZrB2 on
TiB2 particles in the melt They claim that the
nucleation is on TiB2 particles adsorbing of Ti,
when Zr element is present, the titanium
borides will be covered with a monolayer of
zirconium borides preventing the dissolved Ti
frombeingadsorbed[13].
On the contrary, when 0.12%Zr is added
into the melt, the grain refinement performance
of AlTiC refiner with 0.2% addition level was
affected at higher temp. (i.e. 800°C)[13]. Zr
element interact with both TiAl3 and TiC
phases, if both of them are present, Zr
preferentially reacts with TiAl3 phase. Thus
TiCAl is a effective grain refiner at lower
refiningtemperatures.
A combination of small quantities of Fe,
Cr, Si (0.2 wt% Cr) has shown early and
significant fading. At higher Cr concentration
(Cr 2wt %) has adverse effect of coarse ring
grainsize[07].
Agglomeration
The boride agglomeration takes place only
in case ofAlTiB grain refiner. The user can not
be certain that the agglomerate will disperse on
addition to aluminum. It is also possible that
the agglomerate may form within the
customer’s own process. The causes of boride
agglomeration are: TiB2 particles collide with
each other, TiB2 particles are attracted to oxide
films, to form complex agglomerate, halogen
elements “wet” TiB2 particles causing them to
easily agglomerate and TiAl3 layers on TiB2
cansticktheparticlestogether.
Inclusions, in grain refining master alloys
and aluminum alloys as TiB2 agglomerates,
manifest themselves in various forms such as
rings, clusters and strings. Boride
agglomerates are generally classified as
defects when they are above 5 micron in size.
They are often observed to be tiny clusters of
much smaller particles (½ to 1 micron).
Fig.13 : Optical Microstructure of TiBAl 5/1
at 1000x having TiB2 Agglomeration and String
Type Defects
Examination of fractured samples to
investigate the boride agglomeration (as
strings) contains fluorine at relatively higher
levels.TiB2 particles are susceptible to wetting
by fluorides [04]. This can also be identified in
grain refiner microstructure as shown (grain
refinerwithdefects)
The chances of agglomeration of TiB2
particles in lower boron containing grain
refiner is less (e.g.TiBAl 5/0.2). ReducedTiB2
agglomeration to allow thinner foils and
brighter trim alloys to be produced. In case of
TiCAl,TiC a particle doesn't agglomerate, thus
TiCAlissuitablefor allapplications.
Conclusion
lGrain refiners play a crucial role in
aluminum alloys; it improves mechanical
properties that are uniform throughout the
casting, better feeding to eliminate shrinkage
porosity, better strength and fatigue life and is
achieved by heterogeneous nucleation and
growthofgrains.
TiCAl offers advantages in alloys
containing Zr/Cr which can otherwise poison
TiBAl refiner. Al-3% Ti-0.15% C improves
melt fluidity and finished cast appearance in
comparison toAl-3% Ti-1% B in 5XXX series
alloysinparticular,butalsoin6XXX alloys
For lithographic/Strip casting/foil grade
application Al-5%Ti-0.2%B is more effective
grain refiner than compared to Al-3%Ti-
0.2%C and 3%TiAl. As lower boron
concentration leads to less agglomeration of
TiB2particles
And in modifiers Sr is preferred over Na
metal modifier in Al-foundry due to
environmental restrictions. But excess amount
of Sr cause overmodification by coarsening of
Silicon structure which is not easily assessejd
byopticalmicrostructurestudy.
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Technology