The effect of cerium melt treatment on microstructure and mechanical properties of gravity die ca... more The effect of cerium melt treatment on microstructure and mechanical properties of gravity die cast Al-8% Si alloy was studied. The addition of Ce transformed the large columnar α-Al grains into fine equiaxed grains and modified the acicular eutectic Si into fine fibrous form. The addition of Ce resulted in the formation of needle-shaped complex Ce intermetallic along the grain boundaries. Electrical conductivity measurements are used for the first time to reveal the effect of Ce addition on modification of the eutectic Si. The electrical conductivity of the alloy increased with Ce melt treatment. Scanning Electron Microscopy results suggests that the Ce particles did not heterogeneously nucleate the α-Al grains, instead the fine equiaxed grains were formed through an invariant reaction between the liquid melt and Ce phase. The ultimate tensile strength, % elongation and hardness of the alloy significantly improved due to simultaneous modification and refinement.
The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique... more The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique of thermal analysis. The solidification events were determined using cooling curve and its first derivative curve. The microstructure and chemical composition of various phases in the alloy were studied using EDS, SEM and XRD techniques. It was found that the addition of Ce did not cause formation of new phases. However, it hinders the nucleation of stable β dendrites in the alloy. The presence of Ce promotes the eutectoid phase transformation and increases the hardness of the alloy. Latent heat of solidification and heat of eutectoid transformation were found to increase on Ce addition. The upward solidification of the alloy against Cu chill was analysed. Chilling had significant influence on solidification parameters, and caused refinement of the microstructure. The addition of Ce to the melt had no effect during chill casting of the alloy. 1. Introduction Zinc–Aluminium base alloys are used for many industrial applications by virtue of their excellent physical and mechanical properties such as good machinability, high as-cast strength, excellent bearing properties, corrosion resistance, fine surface finish, ability to cast thin sections, as well as low energy requirements (for melting). Among ZA alloys only ZA8 can be hot chamber die cast due to its low melting point. This reduces the production cost of ZA8 for industrial purpose compared to that of other ZA alloys [1,2]. The mechanical properties of ZA alloys mainly depend on the presence and amount of various impurities, and the final microstructure of casting [2]. The effect of melt treatment on the cooling curve, microstructure and various mechanical properties of the alloy is discussed by various researchers. Turk et al. studied the effect of addition of Mn on the microstructure and mechanical properties of ZA8 alloy. The addition of Mn modifies the as cast microstructure by refining the β dendrites and increasing the amount of eutectic phase, and also forms a fine and irregularly shaped intermetallic compound (MnAl6). The hardness and creep strength of the ZA8 alloy increased with manganese content, whereas 0.2% yield, tensile and impact strengths of the alloy improved with increasing Mn up to 0.045 wt-% and then reduced with a further increase in manganese. [1]. Turk et al. reported that ZA-8 alloy when modified with Pb, Sn and Cd resulted in higher wear resistance. Metallographic studies showed that the addition of Pb, Sn and Cd resulted in modification of the microstructure of ZA8 alloy [3]. Ramesh et al. studied the effect of Mn addition to ZA8 alloy on thermal analysis parameters, heat transfer and microstructure. The addition of Mn to ZA8 alloy increased the contact angle, indicating decreased wettability of the modified alloy on the chill surface. The microstructure of ZA8 with Mn showed an increased amount of β phase and a decreased amount of eutectic [2]. Ramesh and Prabhu found that the chill material and coating had a significant effect on the cooling curve of ZA8 alloy. It
In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast ... more In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (R a) and arithmetical mean of the absolute departures of the waviness profile from the centre line (W a) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35µm and 13µm respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.
Corrosion behavior of austempered ductile iron (ADI) in iron ore slurry was studied as a function... more Corrosion behavior of austempered ductile iron (ADI) in iron ore slurry was studied as a function of the microstructure developed by austempering at 380 and 300°C for different exposure time in the slurry. The corrosion rates of the ADI balls immersed in the iron ore slurry was determined using weight loss method. It was found that the pH of the iron ore slurry increased with time and the corrosion behavior is also influenced by the pH of the slurry and the austempering treatment. The ADI austempered at higher temperature showed better corrosion resistance than the ones austempered at lower temperature. The complex nature of corrosion of ADI is influenced by contents of retained austenite, ferrite and the carbon content in a collective way.
Thermal analysis of Al–Si alloys is very useful for the non-destructive evaluation of the melt qu... more Thermal analysis of Al–Si alloys is very useful for the non-destructive evaluation of the melt quality. The present work aimed at the study of the effect of addition of Ce and Sr on cooling curve parameters, microstructure and mechanical properties of Al–8Si–2Cu alloy. The thermal analysis parameters of melt treated alloys were determined. The addition of Ce influenced both primary and eutectic phase nucleation temperatures, whereas, Sr affected only the eutectic nucleation temperature. The depression in the eutectic arrest temperature was higher with Sr addition when compared to Ce. Consequently, a high degree of modification was achieved with Sr. The addition of Ce yielded fine equiaxed a-aluminium grains and Sr treatment resulted in columnar grains. The mechanical properties of the alloy significantly improved on simultaneous addition of Ce and Sr. The individual addition of Sr, Ce and combined addition of Ce ? Sr to base alloy increased the tensile strength by about 40, 52 and 83 % respectively.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination ... more Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined.
The present work involves the study of the effect of varying concentration of Ce addition on micr... more The present work involves the study of the effect of varying concentration of Ce addition on microstructure and mechanical properties of Al-23%Si alloys. Melt-treated alloys were solidified in copper, brass, stainless steel molds to assess the effect of cooling rate. The effect on microstructure was assessed by measuring the fineness of primary silicon and eutectic silicon particle characteristics. The Ce melt treatment transformed the coarse and irregular primary silicon into refined polyhedral silicon crystals, and the effect was more significant at higher cooling rates. Although the melt treatment had refined the eutectic silicon at lower cooling rates, it did not show any considerable effect on the eutectic silicon at higher cooling rates. The mechanical properties of the alloy increased significantly with increase in cooling rates and cerium concentration. Analysis of the results and literature reveals that the refined primary silicon was formed as a result of an invariant reaction between Ce compounds and primary silicon at higher temperatures.
Aluminum-silicon alloy A356 was exposed to different durations at various solutionizing and agein... more Aluminum-silicon alloy A356 was exposed to different durations at various solutionizing and ageing temperatures before and after strontium modification. The effect of Sr-modification on the microstructures and hardness were examined as a function of heat treatment parameters (temperature and time). The combination of Sr-modification and heat treatment increased the hardness of the alloy. The Sr-modification process also influenced the heat treatment parameters of the alloy as it decreased the solutionizing time by 4 hrs and increased the ageing time by 2 hrs to obtain the peak hardness. It was deduced that the modification favored the spheroidization of eutectic silicon to decrease the solutionizing time, however, the increase in ageing time was due to the interaction of modifiers with the Mg2Si precipitates.
The effect of Sr modification of Al-7%Si alloy on casting/chill interfacial heat flux transients ... more The effect of Sr modification of Al-7%Si alloy on casting/chill interfacial heat flux transients was investigated. The alloy was solidified against polished surfaces of copper, brass and cast iron chills. The heat flux across the casting/chill interface was estimated using inverse modeling technique. On modification melt treatment, the peak heat flux increased by about 70%, 24% and 22% for copper, brass and cast iron chills respectively. The effect of Sr modification on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of anair gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line, within a sampling length(R a) and arithmetical mean of the absolute departures of the waviness profile from the centre line within a sampling length(W a) were reduced by 50% on modification. The enhancement in heat transfer achieved due to modification was attributed to the decrease in gap width formed at the interface. The width of the gap formed for the unmodified and modified casting surfaces at the periphery were found to be about 35μm and 19μm respectively. The gap width was used to determine the variation of heat transfer coefficient (HTC) acrossthe chill surface after the formation of stable solid shell.It was found that the HTC decreased along the radial direction.
The effect of cerium melt treatment on microstructure and mechanical properties of gravity die ca... more The effect of cerium melt treatment on microstructure and mechanical properties of gravity die cast Al-8% Si alloy was studied. The addition of Ce transformed the large columnar α-Al grains into fine equiaxed grains and modified the acicular eutectic Si into fine fibrous form. The addition of Ce resulted in the formation of needle-shaped complex Ce intermetallic along the grain boundaries. Electrical conductivity measurements are used for the first time to reveal the effect of Ce addition on modification of the eutectic Si. The electrical conductivity of the alloy increased with Ce melt treatment. Scanning Electron Microscopy results suggests that the Ce particles did not heterogeneously nucleate the α-Al grains, instead the fine equiaxed grains were formed through an invariant reaction between the liquid melt and Ce phase. The ultimate tensile strength, % elongation and hardness of the alloy significantly improved due to simultaneous modification and refinement.
In the present investigation, pure cerium ingots were added to Al-8% Si alloy melt to study its e... more In the present investigation, pure cerium ingots were added to Al-8% Si alloy melt to study its effect on the microstructure and cooling curve parameters. The melt treated alloy was solidified against sand base, stainless steel, brass, and copper chills to study the effect of chilling. Ce treated alloys solidified against sand base resulted in refinement of the eutectic silicon along with the formation of Al-Si-Ce ternary intermetallic compound. Addition of Ce to alloys solidified against chills resulted in the complete modification of eutectic silicon. Thermal analysis results revealed that the nucleation temperatures of eutectic silicon decreased on addition of cerium to the chilled alloys due to the synergistic effect of chilling and cerium addition. The degree of modification achieved was higher due to the decrease in the formation of Ce intermetallics at higher cooling rates.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the
determination ... more Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined.
Al–14%Si alloys, with and without cerium, were cast at varying cooling rates by solidifying them ... more Al–14%Si alloys, with and without cerium, were cast at varying cooling rates by solidifying them in a crucible and against chills. The effect of melt treatment and chilling on microstructure and cooling curve parameters of the alloy was assessed. Ce treated alloys solidified in clay graphite crucible at a slow cooling rate showed refinement of primary silicon and the formation of Al–Si–Ce ternary intermetallic compound. The addition of Ce to the alloy solidified against chills resulted in simultaneous refinement and modification of primary and eutectic silicon. Nucleation temperatures of both primary and eutectic silicon decreased on addition of cerium. The formation of the intermetallic compound decreased with increase in cooling rate, leading to the modification of the eutectic silicon. The increase in the degree of modification of the eutectic Si was associated with the decrease in the volume fraction of the intermetallic compound formed.
Thermal analysis of LM29 alloy and Ce added
LM29 alloys was carried out. The effect of cerium add... more Thermal analysis of LM29 alloy and Ce added LM29 alloys was carried out. The effect of cerium addition on solidification parameters and microstructural features of hypereutectic Al-Si (LM29) alloy was studied using Newtonian analysis technique. Thermal analysis parameters such as primary and eutectic phase nucleation and solidus temperatures were determined. The addition of Ce to LM29 alloy decreased the nucleation temperature of primary silicon and eutectic silicon. The microstructural examination of Ce added LM29 alloys revealed the presence of a polyhedral shaped Al–Si–Ce compound that might have caused the refinement of primary and eutectic silicon. The dendrite coherency point temperature of LM29 alloy was found to be suppressed on addition of Ce.
Al–Si alloys with silicon content more than
13 % are termed as hypereutectic alloys. In recent ye... more Al–Si alloys with silicon content more than 13 % are termed as hypereutectic alloys. In recent years, these alloys have drawn the attention of researchers due to their ability to replace cast iron parts in the transportation industry. The properties of the hypereutectic alloy are greatly dependent on the morphology, size and distribution of primary silicon crystals in the alloy. Mechanical properties of the hypereutectic Al–Si alloy can be improved by the simultaneous refinement and modification of the primary and eutectic silicon and by controlling the solidification parameters. In this paper, the effect of solidification rate and melt treatment on the evolution of microstructure in hypereutectic Al–Si alloys are reviewed. Different types of primary silicon morphology and the conditions for its nucleation and growth are explained. The paper discusses the effect of refinement/modification treatments on the microstructure and properties of the hypereutectic Al-Si alloy. The importance and effect of processing variables and phosphorus refinement on the silicon morphology and wear properties of the alloy is highlighted
The present work deals with the melt treatment of LM30 hypereutectic Al-Si alloy using
cerium and... more The present work deals with the melt treatment of LM30 hypereutectic Al-Si alloy using cerium and strontium and the assessment of its effect on microstructure and properties of the alloy. The addition of cerium simultaneously modified both primary and eutectic silicon, leading to an increase in ultimate tensile strength, as well as the wear resistance of the alloy. It was found that the coefficient of thermal expansion of the alloy decreased on modification of the microstructure.
The effect of cerium melt treatment on microstructure and mechanical properties of gravity die ca... more The effect of cerium melt treatment on microstructure and mechanical properties of gravity die cast Al-8% Si alloy was studied. The addition of Ce transformed the large columnar α-Al grains into fine equiaxed grains and modified the acicular eutectic Si into fine fibrous form. The addition of Ce resulted in the formation of needle-shaped complex Ce intermetallic along the grain boundaries. Electrical conductivity measurements are used for the first time to reveal the effect of Ce addition on modification of the eutectic Si. The electrical conductivity of the alloy increased with Ce melt treatment. Scanning Electron Microscopy results suggests that the Ce particles did not heterogeneously nucleate the α-Al grains, instead the fine equiaxed grains were formed through an invariant reaction between the liquid melt and Ce phase. The ultimate tensile strength, % elongation and hardness of the alloy significantly improved due to simultaneous modification and refinement.
The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique... more The solidification path of ZA8 alloy with Ce addition was characterized using Newtonian technique of thermal analysis. The solidification events were determined using cooling curve and its first derivative curve. The microstructure and chemical composition of various phases in the alloy were studied using EDS, SEM and XRD techniques. It was found that the addition of Ce did not cause formation of new phases. However, it hinders the nucleation of stable β dendrites in the alloy. The presence of Ce promotes the eutectoid phase transformation and increases the hardness of the alloy. Latent heat of solidification and heat of eutectoid transformation were found to increase on Ce addition. The upward solidification of the alloy against Cu chill was analysed. Chilling had significant influence on solidification parameters, and caused refinement of the microstructure. The addition of Ce to the melt had no effect during chill casting of the alloy. 1. Introduction Zinc–Aluminium base alloys are used for many industrial applications by virtue of their excellent physical and mechanical properties such as good machinability, high as-cast strength, excellent bearing properties, corrosion resistance, fine surface finish, ability to cast thin sections, as well as low energy requirements (for melting). Among ZA alloys only ZA8 can be hot chamber die cast due to its low melting point. This reduces the production cost of ZA8 for industrial purpose compared to that of other ZA alloys [1,2]. The mechanical properties of ZA alloys mainly depend on the presence and amount of various impurities, and the final microstructure of casting [2]. The effect of melt treatment on the cooling curve, microstructure and various mechanical properties of the alloy is discussed by various researchers. Turk et al. studied the effect of addition of Mn on the microstructure and mechanical properties of ZA8 alloy. The addition of Mn modifies the as cast microstructure by refining the β dendrites and increasing the amount of eutectic phase, and also forms a fine and irregularly shaped intermetallic compound (MnAl6). The hardness and creep strength of the ZA8 alloy increased with manganese content, whereas 0.2% yield, tensile and impact strengths of the alloy improved with increasing Mn up to 0.045 wt-% and then reduced with a further increase in manganese. [1]. Turk et al. reported that ZA-8 alloy when modified with Pb, Sn and Cd resulted in higher wear resistance. Metallographic studies showed that the addition of Pb, Sn and Cd resulted in modification of the microstructure of ZA8 alloy [3]. Ramesh et al. studied the effect of Mn addition to ZA8 alloy on thermal analysis parameters, heat transfer and microstructure. The addition of Mn to ZA8 alloy increased the contact angle, indicating decreased wettability of the modified alloy on the chill surface. The microstructure of ZA8 with Mn showed an increased amount of β phase and a decreased amount of eutectic [2]. Ramesh and Prabhu found that the chill material and coating had a significant effect on the cooling curve of ZA8 alloy. It
In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast ... more In the present investigation, Al-14 wt. % Si alloy was solidified against copper, brass and cast iron chills, to study the effect of Ce melt treatment on casting/chill interfacial heat flux transients and casting surface profile. The heat flux across the casting/chill interface was estimated using inverse modelling technique. On addition of 1.5% Ce, the peak heat flux increased by about 38%, 42% and 43% for copper, brass and cast iron chills respectively. The effect of Ce addition on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of an air gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line (R a) and arithmetical mean of the absolute departures of the waviness profile from the centre line (W a) were found to decrease on Ce addition. The interfacial gap width formed for the unmodified and Ce treated casting surfaces at the periphery were found to be about 35µm and 13µm respectively. The enhancement in heat transfer on addition of Ce addition was attributed to the lowering of the surface tension of the liquid melt. The gap width at the interface was used to determine the variation of heat transfer coefficient (HTC) across the chill surface after the formation of stable solid shell. It was found that the HTC decreased along the radial direction for copper and brass chills and increased along radial direction for cast iron chills.
Corrosion behavior of austempered ductile iron (ADI) in iron ore slurry was studied as a function... more Corrosion behavior of austempered ductile iron (ADI) in iron ore slurry was studied as a function of the microstructure developed by austempering at 380 and 300°C for different exposure time in the slurry. The corrosion rates of the ADI balls immersed in the iron ore slurry was determined using weight loss method. It was found that the pH of the iron ore slurry increased with time and the corrosion behavior is also influenced by the pH of the slurry and the austempering treatment. The ADI austempered at higher temperature showed better corrosion resistance than the ones austempered at lower temperature. The complex nature of corrosion of ADI is influenced by contents of retained austenite, ferrite and the carbon content in a collective way.
Thermal analysis of Al–Si alloys is very useful for the non-destructive evaluation of the melt qu... more Thermal analysis of Al–Si alloys is very useful for the non-destructive evaluation of the melt quality. The present work aimed at the study of the effect of addition of Ce and Sr on cooling curve parameters, microstructure and mechanical properties of Al–8Si–2Cu alloy. The thermal analysis parameters of melt treated alloys were determined. The addition of Ce influenced both primary and eutectic phase nucleation temperatures, whereas, Sr affected only the eutectic nucleation temperature. The depression in the eutectic arrest temperature was higher with Sr addition when compared to Ce. Consequently, a high degree of modification was achieved with Sr. The addition of Ce yielded fine equiaxed a-aluminium grains and Sr treatment resulted in columnar grains. The mechanical properties of the alloy significantly improved on simultaneous addition of Ce and Sr. The individual addition of Sr, Ce and combined addition of Ce ? Sr to base alloy increased the tensile strength by about 40, 52 and 83 % respectively.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination ... more Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined.
The present work involves the study of the effect of varying concentration of Ce addition on micr... more The present work involves the study of the effect of varying concentration of Ce addition on microstructure and mechanical properties of Al-23%Si alloys. Melt-treated alloys were solidified in copper, brass, stainless steel molds to assess the effect of cooling rate. The effect on microstructure was assessed by measuring the fineness of primary silicon and eutectic silicon particle characteristics. The Ce melt treatment transformed the coarse and irregular primary silicon into refined polyhedral silicon crystals, and the effect was more significant at higher cooling rates. Although the melt treatment had refined the eutectic silicon at lower cooling rates, it did not show any considerable effect on the eutectic silicon at higher cooling rates. The mechanical properties of the alloy increased significantly with increase in cooling rates and cerium concentration. Analysis of the results and literature reveals that the refined primary silicon was formed as a result of an invariant reaction between Ce compounds and primary silicon at higher temperatures.
Aluminum-silicon alloy A356 was exposed to different durations at various solutionizing and agein... more Aluminum-silicon alloy A356 was exposed to different durations at various solutionizing and ageing temperatures before and after strontium modification. The effect of Sr-modification on the microstructures and hardness were examined as a function of heat treatment parameters (temperature and time). The combination of Sr-modification and heat treatment increased the hardness of the alloy. The Sr-modification process also influenced the heat treatment parameters of the alloy as it decreased the solutionizing time by 4 hrs and increased the ageing time by 2 hrs to obtain the peak hardness. It was deduced that the modification favored the spheroidization of eutectic silicon to decrease the solutionizing time, however, the increase in ageing time was due to the interaction of modifiers with the Mg2Si precipitates.
The effect of Sr modification of Al-7%Si alloy on casting/chill interfacial heat flux transients ... more The effect of Sr modification of Al-7%Si alloy on casting/chill interfacial heat flux transients was investigated. The alloy was solidified against polished surfaces of copper, brass and cast iron chills. The heat flux across the casting/chill interface was estimated using inverse modeling technique. On modification melt treatment, the peak heat flux increased by about 70%, 24% and 22% for copper, brass and cast iron chills respectively. The effect of Sr modification on casting surface texture was analyzed using a surface profilometer. The surface profile of the casting and the chill surfaces clearly indicated the formation of anair gap at the periphery of the casting. The arithmetic average value of the profile departure from the mean line, within a sampling length(R a) and arithmetical mean of the absolute departures of the waviness profile from the centre line within a sampling length(W a) were reduced by 50% on modification. The enhancement in heat transfer achieved due to modification was attributed to the decrease in gap width formed at the interface. The width of the gap formed for the unmodified and modified casting surfaces at the periphery were found to be about 35μm and 19μm respectively. The gap width was used to determine the variation of heat transfer coefficient (HTC) acrossthe chill surface after the formation of stable solid shell.It was found that the HTC decreased along the radial direction.
The effect of cerium melt treatment on microstructure and mechanical properties of gravity die ca... more The effect of cerium melt treatment on microstructure and mechanical properties of gravity die cast Al-8% Si alloy was studied. The addition of Ce transformed the large columnar α-Al grains into fine equiaxed grains and modified the acicular eutectic Si into fine fibrous form. The addition of Ce resulted in the formation of needle-shaped complex Ce intermetallic along the grain boundaries. Electrical conductivity measurements are used for the first time to reveal the effect of Ce addition on modification of the eutectic Si. The electrical conductivity of the alloy increased with Ce melt treatment. Scanning Electron Microscopy results suggests that the Ce particles did not heterogeneously nucleate the α-Al grains, instead the fine equiaxed grains were formed through an invariant reaction between the liquid melt and Ce phase. The ultimate tensile strength, % elongation and hardness of the alloy significantly improved due to simultaneous modification and refinement.
In the present investigation, pure cerium ingots were added to Al-8% Si alloy melt to study its e... more In the present investigation, pure cerium ingots were added to Al-8% Si alloy melt to study its effect on the microstructure and cooling curve parameters. The melt treated alloy was solidified against sand base, stainless steel, brass, and copper chills to study the effect of chilling. Ce treated alloys solidified against sand base resulted in refinement of the eutectic silicon along with the formation of Al-Si-Ce ternary intermetallic compound. Addition of Ce to alloys solidified against chills resulted in the complete modification of eutectic silicon. Thermal analysis results revealed that the nucleation temperatures of eutectic silicon decreased on addition of cerium to the chilled alloys due to the synergistic effect of chilling and cerium addition. The degree of modification achieved was higher due to the decrease in the formation of Ce intermetallics at higher cooling rates.
Computer aided cooling curve analysis (CACCA) is an online prediction tool for the
determination ... more Computer aided cooling curve analysis (CACCA) is an online prediction tool for the determination of solidification characteristics of metals or alloys. The results of CACCA can be used to accurately determine latent heat and solid fraction needed for modeling of the solidification process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper describes the theoretical and experimental procedures involved Newtonian and Fourier analysis techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and temperature/time for the alloy were determined.
Al–14%Si alloys, with and without cerium, were cast at varying cooling rates by solidifying them ... more Al–14%Si alloys, with and without cerium, were cast at varying cooling rates by solidifying them in a crucible and against chills. The effect of melt treatment and chilling on microstructure and cooling curve parameters of the alloy was assessed. Ce treated alloys solidified in clay graphite crucible at a slow cooling rate showed refinement of primary silicon and the formation of Al–Si–Ce ternary intermetallic compound. The addition of Ce to the alloy solidified against chills resulted in simultaneous refinement and modification of primary and eutectic silicon. Nucleation temperatures of both primary and eutectic silicon decreased on addition of cerium. The formation of the intermetallic compound decreased with increase in cooling rate, leading to the modification of the eutectic silicon. The increase in the degree of modification of the eutectic Si was associated with the decrease in the volume fraction of the intermetallic compound formed.
Thermal analysis of LM29 alloy and Ce added
LM29 alloys was carried out. The effect of cerium add... more Thermal analysis of LM29 alloy and Ce added LM29 alloys was carried out. The effect of cerium addition on solidification parameters and microstructural features of hypereutectic Al-Si (LM29) alloy was studied using Newtonian analysis technique. Thermal analysis parameters such as primary and eutectic phase nucleation and solidus temperatures were determined. The addition of Ce to LM29 alloy decreased the nucleation temperature of primary silicon and eutectic silicon. The microstructural examination of Ce added LM29 alloys revealed the presence of a polyhedral shaped Al–Si–Ce compound that might have caused the refinement of primary and eutectic silicon. The dendrite coherency point temperature of LM29 alloy was found to be suppressed on addition of Ce.
Al–Si alloys with silicon content more than
13 % are termed as hypereutectic alloys. In recent ye... more Al–Si alloys with silicon content more than 13 % are termed as hypereutectic alloys. In recent years, these alloys have drawn the attention of researchers due to their ability to replace cast iron parts in the transportation industry. The properties of the hypereutectic alloy are greatly dependent on the morphology, size and distribution of primary silicon crystals in the alloy. Mechanical properties of the hypereutectic Al–Si alloy can be improved by the simultaneous refinement and modification of the primary and eutectic silicon and by controlling the solidification parameters. In this paper, the effect of solidification rate and melt treatment on the evolution of microstructure in hypereutectic Al–Si alloys are reviewed. Different types of primary silicon morphology and the conditions for its nucleation and growth are explained. The paper discusses the effect of refinement/modification treatments on the microstructure and properties of the hypereutectic Al-Si alloy. The importance and effect of processing variables and phosphorus refinement on the silicon morphology and wear properties of the alloy is highlighted
The present work deals with the melt treatment of LM30 hypereutectic Al-Si alloy using
cerium and... more The present work deals with the melt treatment of LM30 hypereutectic Al-Si alloy using cerium and strontium and the assessment of its effect on microstructure and properties of the alloy. The addition of cerium simultaneously modified both primary and eutectic silicon, leading to an increase in ultimate tensile strength, as well as the wear resistance of the alloy. It was found that the coefficient of thermal expansion of the alloy decreased on modification of the microstructure.
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Papers by vijeesh v
determination of solidification characteristics of metals or alloys. The results of CACCA can be
used to accurately determine latent heat and solid fraction needed for modeling of the solidification
process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the
first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper
describes the theoretical and experimental procedures involved Newtonian and Fourier analysis
techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and
temperature/time for the alloy were determined.
a crucible and against chills. The effect of melt treatment and chilling on microstructure and
cooling curve parameters of the alloy was assessed. Ce treated alloys solidified in clay graphite
crucible at a slow cooling rate showed refinement of primary silicon and the formation of Al–Si–Ce
ternary intermetallic compound. The addition of Ce to the alloy solidified against chills resulted in
simultaneous refinement and modification of primary and eutectic silicon. Nucleation temperatures
of both primary and eutectic silicon decreased on addition of cerium. The formation of the
intermetallic compound decreased with increase in cooling rate, leading to the modification of the
eutectic silicon. The increase in the degree of modification of the eutectic Si was associated with
the decrease in the volume fraction of the intermetallic compound formed.
LM29 alloys was carried out. The effect of cerium addition
on solidification parameters and microstructural features of
hypereutectic Al-Si (LM29) alloy was studied using
Newtonian analysis technique. Thermal analysis parameters
such as primary and eutectic phase nucleation and
solidus temperatures were determined. The addition of Ce
to LM29 alloy decreased the nucleation temperature of
primary silicon and eutectic silicon. The microstructural
examination of Ce added LM29 alloys revealed the presence
of a polyhedral shaped Al–Si–Ce compound that
might have caused the refinement of primary and eutectic
silicon. The dendrite coherency point temperature of LM29
alloy was found to be suppressed on addition of Ce.
13 % are termed as hypereutectic alloys. In recent years,
these alloys have drawn the attention of researchers due to
their ability to replace cast iron parts in the transportation
industry. The properties of the hypereutectic alloy are
greatly dependent on the morphology, size and distribution
of primary silicon crystals in the alloy. Mechanical properties
of the hypereutectic Al–Si alloy can be improved by
the simultaneous refinement and modification of the primary
and eutectic silicon and by controlling the solidification
parameters. In this paper, the effect of solidification
rate and melt treatment on the evolution of microstructure
in hypereutectic Al–Si alloys are reviewed. Different types
of primary silicon morphology and the conditions for its
nucleation and growth are explained. The paper discusses
the effect of refinement/modification treatments on the
microstructure and properties of the hypereutectic Al-Si
alloy. The importance and effect of processing variables
and phosphorus refinement on the silicon morphology and
wear properties of the alloy is highlighted
cerium and strontium and the assessment of its effect on microstructure and properties of the alloy. The addition
of cerium simultaneously modified both primary and eutectic silicon, leading to an increase in ultimate
tensile strength, as well as the wear resistance of the alloy. It was found that the coefficient of thermal expansion
of the alloy decreased on modification of the microstructure.
determination of solidification characteristics of metals or alloys. The results of CACCA can be
used to accurately determine latent heat and solid fraction needed for modeling of the solidification
process. Newtonian and Fourier analysis techniques adopt a data base line fitting technique to the
first derivative curve for calculation of the solid fraction and latent heat of solidification. This paper
describes the theoretical and experimental procedures involved Newtonian and Fourier analysis
techniques with reference to an Al-22% Si alloy. The correlations between the solid fraction and
temperature/time for the alloy were determined.
a crucible and against chills. The effect of melt treatment and chilling on microstructure and
cooling curve parameters of the alloy was assessed. Ce treated alloys solidified in clay graphite
crucible at a slow cooling rate showed refinement of primary silicon and the formation of Al–Si–Ce
ternary intermetallic compound. The addition of Ce to the alloy solidified against chills resulted in
simultaneous refinement and modification of primary and eutectic silicon. Nucleation temperatures
of both primary and eutectic silicon decreased on addition of cerium. The formation of the
intermetallic compound decreased with increase in cooling rate, leading to the modification of the
eutectic silicon. The increase in the degree of modification of the eutectic Si was associated with
the decrease in the volume fraction of the intermetallic compound formed.
LM29 alloys was carried out. The effect of cerium addition
on solidification parameters and microstructural features of
hypereutectic Al-Si (LM29) alloy was studied using
Newtonian analysis technique. Thermal analysis parameters
such as primary and eutectic phase nucleation and
solidus temperatures were determined. The addition of Ce
to LM29 alloy decreased the nucleation temperature of
primary silicon and eutectic silicon. The microstructural
examination of Ce added LM29 alloys revealed the presence
of a polyhedral shaped Al–Si–Ce compound that
might have caused the refinement of primary and eutectic
silicon. The dendrite coherency point temperature of LM29
alloy was found to be suppressed on addition of Ce.
13 % are termed as hypereutectic alloys. In recent years,
these alloys have drawn the attention of researchers due to
their ability to replace cast iron parts in the transportation
industry. The properties of the hypereutectic alloy are
greatly dependent on the morphology, size and distribution
of primary silicon crystals in the alloy. Mechanical properties
of the hypereutectic Al–Si alloy can be improved by
the simultaneous refinement and modification of the primary
and eutectic silicon and by controlling the solidification
parameters. In this paper, the effect of solidification
rate and melt treatment on the evolution of microstructure
in hypereutectic Al–Si alloys are reviewed. Different types
of primary silicon morphology and the conditions for its
nucleation and growth are explained. The paper discusses
the effect of refinement/modification treatments on the
microstructure and properties of the hypereutectic Al-Si
alloy. The importance and effect of processing variables
and phosphorus refinement on the silicon morphology and
wear properties of the alloy is highlighted
cerium and strontium and the assessment of its effect on microstructure and properties of the alloy. The addition
of cerium simultaneously modified both primary and eutectic silicon, leading to an increase in ultimate
tensile strength, as well as the wear resistance of the alloy. It was found that the coefficient of thermal expansion
of the alloy decreased on modification of the microstructure.