Processing-microstructure-mechanical properties of an Al-Cu/SiC metal matrix composite synthesized using disintegrated melt deposition technique

In the present study, an aluminum based metallic matrix (Al-2wt. % Cu) was reinforced with SiC particulates using a new disintegrated melt deposition technique. Microstructural characterization studies conducted on the samples taken from disintegrated melt deposition technique revealed a columnar-equiaxed matrix microstructure, finite amount of porosity and uniform distribution of SiC particulates. Results of ambient temperature mechanical tests demonstrate an increase in 0.2% Y.S and UTS and decrease in ductility of samples taken from disintegrated melt deposition technique when compared to the unreinforced samples. The results of microstructural characterization and mechanical testing were finally rationalized in terms of the processing steps involved in the disintegrated melt deposition technique.     

Effect of Matrix Constitution on Microstructure and Mechanical Properties of Rheocast Metal Matrix Composites

In this study, aluminum-based metallic matrices with varying amounts of copper (I wt.% Cu, 3 wt.% Cu and 4.5 wt.% Cu) were reinforced with SiC particulates using a partial liquid phase casting technique. Microstructural characterization studies conducted on the composite samples revealed an increase in uniformity of distribution of SiC particulates and SiC/Al interfacial integrity and a decrease: in porosity in the metallic matrix with decreasing weight percent of copper. The results of the ageing studies revealed an accelerated ageing kinetics for the Al-1% Cu/SiC composite when compared to Al-3% Cu/SiC and Al-4.5% Cu/SiC samples. Results of ambient temperature mechanical tests demonstrate an increase in 0.2% yield strength and ultimate tensile strength of the composites and a decrease in ductility and strain hardening rate with an increasing weight percent of copper in the metallic matrix. Fracture studies revealed the presence of interfacial debonding, particulate breakage and cracks in the matrix of tensile specimens. The results of microstructural characterization, mechanical testing and fractography were finally rationalized in terms of the effect of variation in weight percent of copper in the metallic matrix.     

Effect of variation in physical properties of the metallic matrix on the microstructural characteristics and the ageing behaviour of Al-Cu/SiC metal matrix composites

In this study, aluminium-based metallic matrices with varying amount of copper (1 wt% Cu and 4.5 wt% Cu) were reinforced with SiC particulates using a partial liquid phase casting technique. The results of the present investigation showed smaller sized and higher weight percent of SiC particulates being successfully incorporated with a decrease in the weight percent of copper in the matrix. Microstructural characterisation studies conducted on the composite samples revealed an increase in uniformity of distribution of SiC particulates, improved SiC/Al interfacial integrity and smaller grain size of the metallic matrices with decreasing weight percent of copper. Results of the microstructural characterisation studies also exhibited the presence of solute rich zone in the near vicinity of SiC particulates and the nucleation of secondary phases both at and in near vicinity of SiC particulates. The result of the ageing studies revealed an accelerated ageing kinetics for the Al-1%Cu/SiC composite when compared to the Al-4.5%Cu/SiC composite samples. The results of accelerated ageing kinetics were rationalised in terms of the effect of variation in the physical properties of the metallic matrix and the ensuing microstructural characteristics due to variation in the amount of copper in the matrix.     

Effect of microstructural features on the ageing behaviour of Al–Cu/SiC metal matrix composites processed using casting and rheocasting routes

In the present study, microstructural variation in Al–2 wt% Cu/SiC composites was accomplished by synthesizing them using conventional casting and partial liquid phase casting (rheocasting) routes. Microstructural characterization studies conducted on the rheocast composite samples revealed a finer grain size, minimal porosity, uniform distribution of SiC particulates, and a superior matrix – particulate interfacial integrity when compared to the conventionally cast composite samples. Furthermore, the results of interfacial characterization studies revealed that the presence of porosity associated with either individual SiC particulate or SiC clusters significantly influence the constitutional characteristics of the interfacial region. Results of ageing studies revealed an accelerated ageing kinetics in case of rheocast samples when compared to the conventionally cast composite samples. The results of ageing studies were finally rationalized in terms of the difference in microstructural characteristics of the rheocast and conventionally cast composite samples. This revised version was published online in November 2006 with corrections to the Cover Date.     

Development of high strength magnesium based composites using elemental nickel particulates as reinforcement

Magnesium based materials due to their inherently low density and ensuing potential to exhibit high specific mechanical properties are actively sought for weight-critical structural application. In the present study, elemental and nickel reinforced magnesium materials were synthesized using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the composite samples showed uniform distribution of nickel particulates in the matrix material, good interfacial integrity of magnesium matrix with nickel particulates and Mg-Ni based intermetallics, and the presence of minimal porosity. Physical properties characterization revealed that addition of nickel as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterization revealed that the presence of nickel reinforcement lead to significant improvement in hardness, elastic modulus, 0.2% yield strength and UTS while the ductility was adversely affected. The results further revealed that the combination of 0.2% yield strength, UTS, and ductility exhibited by nickel reinforced magnesium remained much superior even when compared to high strength magnesium alloy AZ91 reinforced with much higher volume percentage of SiC. An attempt is made in the present study to correlate the effect of nickel as reinforcement and its increasing amount with the microstructural, physical and mechanical properties of magnesium.     

Synthesis, microstructure and properties characterization of disintegrated melt deposited Mg/SiC composites

In the present study, elemental and silicon carbide reinforced magnesium materials were synthesized using an innovative disintegrated melt deposition method followed by hot extrusion. Microstructural characterization studies revealed the presence of minimal porosity and completely recrystallized matrix in all the unreinforced and reinforced samples. In the case of reinforced magnesium samples, a fairly uniform distribution of SiC particulates and good SiC-Mg interfacial integrity was realized. The results of microhardness measurements revealed an increase in the brittleness of the SiC-Mg interfacial region with an increase in the amount of SiC particulates. Results of physical and mechanical properties characterization revealed that the increasing presence of SiC particulates led to an increase in hardness and elastic modulus, does not affect 0.2% yield strength and reduces the ultimate tensile strength, ductility, work for fracture and coefficient of thermal expansion. An attempt is made to correlate the results of physical and mechanical properties testing with that of the microstructural characterization.     

Improving mechanical performance of Al by using Ti as reinforcement

In the present study, Al based composite reinforced with Ti particulates was fabricated by using the disintegrated melt deposition (DMD) processing technique followed by hot extrusion. Microstructural characterization of the as-extruded composite samples revealed a near uniform distribution of the Ti particulates in the Al matrix, good interfacial integrity between the Ti particulates and the Al matrix and minimal presence of porosity. Mechanical properties characterization revealed that the addition of Ti particulates resulted in an increase in macrohardness, 0.2% YS, UTS and elastic modulus. However, the ductility of the composite was found to be decreased by the addition of Ti particulates in the Al matrix. The fractured samples of the composite showed the ductile mode of fracture in the case of Al matrix whilst particle fracture and debonding were observed as the failure mode of the Ti reinforcement.     

Synthesis, characterization and mechanical properties of nano alumina particulate reinforced magnesium based bulk metallic glass composites

Mg₆₇Zn₂₈Ca₅ bulk metallic glass reinforced with 0.66-1.5 vol% of nano alumina particulates were successfully synthesized using disintegrated melt deposition technique. Microstructural characterization revealed reasonably uniform distribution of alumina particulates in a metallic glass matrix. The reinforced particles have no significant effect on the glass forming ability of the monolithic glass matrix. Mechanical characterization under compressive loading showed improved micro hardness, fracture strength and failure strain with increase in nano alumina particulate reinforcement. The best combination of strength, hardness and ductility was observed in Mg/1.5 vol% alumina composite with fracture strength of 780 MPa and 2.6% failure strain.     

Development of high strength magnesium copper based hybrid composites with enhanced tensile properties

Abstract

The requirements for reduced fuel consumption and limited emission have triggered high consumption of magnesium in recent years due to its inherently low density and ensuing potential to exhibit advantageous specific mechanical properties. In the present study, monolithic and copper particulate reinforced magnesium composites were synthesised using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the composite samples showed uniform distribution of Cu and Mg- Cu based intermetallic particulates in the matrix material, good interfacial integrity of the magnesium matrix with reinforcement particulates, and the presence of minimal porosity. Physical properties characterisation revealed that the addition of copper as reinforcement marginally reduced the coefficient of thermal expansion (CTE) of pure magnesium. Mechanical properties characterisation revealed that the addition of copper in magnesium led to significant improvement in hardness, elastic modulus, 0.2% yield strength and UTS, while the ductility was adversely affected. The results further revealed that the combination of 0.2% yield strength, UTS, and ductility exhibited by Mg-Cu formulations was superior to that of high strength magnesium alloy AZ91 reinforced with a much higher volume percentage of SiC. An attempt was made in the present study to correlate the effect of the presence of copper and its increasing amount with the microstructural, physical and mechanical properties of the magnesium.     

Using hybrid reinforcement methodology to enhance overall mechanical performance of pure magnesium

In the present study, magnesium based composites containing galvanised iron wire mesh and carbon fibres as continuous reinforcement were fabricated using the disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the extruded composite samples showed minimal porosity and good interfacial integrity between iron wire mesh and the matrix. The penetration of magnesium in between carbon fibres remains limited. Mechanical characterization revealed that the addition of reinforcements lead to an increase in hardness, dynamic modulus and 0.2%YS, did not affect the UTS and reduced the ductility. The overall mechanical performance of the composite with hybrid reinforcement synthesized in this study remained superior when compared to conventional composite formulations with comparatively higher volume fraction of reinforcement.     

Enhancing modulus and ductility of Mg/SiC composite through judicious selection of extrusion temperature and heat treatment

Abstract

In the present study, a magnesium based composite with about 11.5 wt-%SiC particulates was synthesised using an innovative disintegrated melt deposition technique followed by extrusion at different temperatures of 350°C, 250°C, 150°C and 100°C. Microstructural characterisation of the extruded samples showed an increase in alignment of SiC particulates in the direction of extrusion, reduction in number of SiC particulate clusters and improved distribution of the SiC particulates as the extrusion temperature decreased. Good interfacial integrity and minimal porosity was also observed for all the samples. Mechanical properties characterisation revealed that a decrease in extrusion temperature from 350°C to 100°C led to a significant increase in hardness, elastic modulus, 0.2% yield strength while the average UTS and ductility remain unaffected. Subsequently, isothermal heat treatment at 100°C with holding times of 5 and 10 h were also carried out for samples that were extruded at 100°C. The results of tensile testing revealed that the heat treatment led to an approximately 3.6 times increase in ductility, did not affect the modulus. Considering the standard deviation, the 0.2% yield strength and UTS remained similar. An attempt is made in the present study to correlate the effect of decreasing the extrusion temperature as well as subsequent heat treatment with the microstructural and mechanical behaviour of the composite.     

Synthesis and recyclability of a magnesium based composite using an innovative disintegrated melt deposition technique

Abstract

This study has addressed the feasibility of synthesising and recycling a silicon carbide reinforced magnesium composite using an innovative disintegrated melt deposition technique with the aim of improving the mechanical properties. Microstructural characterisation studies revealed a marginal decrease in porosity and reinforcement content, and no change in grain morphology, reinforcement distribution pattern, and interfacial integrity between matrix and reinforcement following recycling. Results of physical and mechanical property characterisation revealed increases in 0.2% yield strength, ultimate tensile strength, ductility, and coefficient of thermal expansion of the recycled specimens when compared with the parent composite. These properties have been rationalised in terms of the microstructural characteristics associated with the disintegrated melt deposited composite specimens. Particular emphasis was placed on studying the effect of recycling on the microstructure and properties of the composite.     

常规铸造工艺条件下SiCp/Al-Si复合材料中的界面反应

采用搅拌复合法制备了10%SiC／Al—5Si—Mg，10%SiC／Al—7Si—Mg(体积分数)复合材料，研究了在常规铸造工艺条件下重熔后复合材料中的界面反应。通过透射电镜和能谱分析可知，SiC界面基本上都是单一的SiC／Al及SiC／Si界面，部分界面上有MgAl2O4颗粒相形成，由于基体合金中Si的存在，生成Al2C3的有害界面化学反应得到了抑制。对不同文献中抑制Al4C3产生所需临界Si含量实验测定结果的差异进行了分析。     

High-temperature tensile properties of Mg/Al2O3 nanocomposite

Mg/1.1Al₂O₃ nanocomposite was synthesized using solidification process called disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization showed that reasonably uniform distribution of reinforcement leads to significant grain refinement of commercially pure magnesium matrix and effectively restricted the grain growth during high-temperature tensile test. Physical properties characterization revealed that addition of nano-Al₂O₃ particulates as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterization revealed that the presence of thermally stable nano-Al₂O₃ particulates as reinforcement leads to a significant increase in room temperature microhardness, dynamic elastic modulus, 0.2% yield strength, UTS and ductility of pure magnesium and efficiently maintained the strengthening effect up to 150 °C. Fractography revealed that fracture behavior of magnesium matrix change from brittle to mixed ductile mode with activation of non-basal slip system in room temperature to complete ductile mode at high temperature due to the presence of nano-Al₂O₃ particulates.     

In Situ Al_2O_3-TiB_2/Al-Cu Composite Fabricated by Reaction Pressing of TiO_2-Al-B-CuO System

The in situ formed Al2O3 and TiB2 particulates reinforced Al-3.3 wt pct Cu alloy composite hasbeen successfully fabricated by reaction pressing of TiO2, Al, B and CuO powders. The in situformed Al2O3 and TiB2 particulates with a size from 10 nm to 2 μm are unifOrmly distributedin the matrix. The composite has a tensiIe Strength of 482 MPa and an elastic modulus of103.3 GPa.     

Effect of temperature in single phase regime on aging response of (Al-2Cu)/SiC metal matrix composite synthesised using disintegrated melt deposition technique

Abstract

In the present study, an aluminium based metal matrix composite ((Al-2 wt-%Cu)/SiC) was synthesised using an innovative disintegrated melt deposition technique and investigated to determine its microstructural characteristics and the effect of temperature in the single phase regime on the peak aging characteristics. Microstructural characterisation carried out on the as processed composite revealed the presence of a dendritic–equiaxed microstructure, non-interconnected porosity, uniform distribution of SiC particles, and good interfacial integrity. The results of solutionising studies indicated that the peak hardness during solutionising can only be realised if the composite is soaked at a critical solutionising temperature. Further, the results also indicated that the time required to attain peak solutionising hardness at various temperatures in the single phase regime is independent of the solutionising temperatures investigated in this study. The results of the aging studies revealed that the maximum hardness following aging is achieved for the composite solutionised at a critical solutionising temperature and time. The results of heat treatment characterisation were finally rationalised in terms of the changes in the constitutional and microstructural features during the various stages of the heat treatment procedure used in the present study.     

Development of Al356/SiCp cast composites by injection of SiCp containing composite powders

One of the great challenges of producing cast metal matrix composites is the agglomeration tendency of the reinforcements. This would normally result in poor distribution of the particles, high porosity content, and low mechanical properties. In the present work, a new method for uniform distribution of very fine SiC particles with average size of less than 3 μm was employed. The key idea was to allow for gradual in situ release of properly wetted SiC particles in the liquid metal. For this purpose, SiC particles were injected into the melt in three different forms, i.e., untreated SiC_p, milled particulate Al–SiC_p composite powder, and milled particulate Al–SiC_p–Mg composite powder. The resultant composite slurries were then cast from either fully liquid (stir casting) or semisolid (compocasting) state. Consequently, the effects of the casting method and the type of the injected powder on the microstructural characteristics as well as the mechanical properties of the cast composites were investigated. The results showed that the distribution of SiC particles in the matrix and the porosity content of the composites were greatly improved by injecting milled composite powders instead of untreated-SiC particles into the melt. Casting from semisolid state instead of fully liquid state had similar effects. The average size of SiC particles incorporated into the matrix was also significantly reduced from about 8 to 3 μm by injecting milled composite powders. The ultimate tensile strength, yield strength and elongation of Al356/5 vol.%SiC_p composite manufactured by compocasting of the (Al–SiC_p–Mg)_cp injected melt were increased by 90%, 103% and 135%, respectively, compared to those of the composite manufactured by stir casting of the untreated-SiC_p injected melt.     

Improvement of microstructure and mechanical properties of AZ91/SiC composite by mechanical alloying

AZ91 magnesium alloy reinforced with SiC particulates was fabricated via powder metallurgy technique as well as mechanical alloying process where a planetary ball mill was employed. Microstructure and mechanical properties of the fabricated AZ91 composites had been evaluated. Microstructural study showed that grain size of the material was refined and SiC particulates were well distributed after mechanical alloying. Mechanical tests of the composite showed an enhanced yield and ultimate tensile strengths for the mechanically alloyed samples compared with those prepared via the powder metallurgical route.     

Effect of nanoscale boron carbide particle addition on the microstructural evolution and mechanical response of pure magnesium

In this study, the effect of nano-B₄C addition on the microstructural and the mechanical behavior of pure Mg are investigated. Pure Mg-metal reinforced with different amounts of nano-size B₄C particulates were synthesized using the disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the developed Mg/x-B₄C composites revealed uniform distribution of nano-B₄C particulates and significant grain refinement. Electron back scattered diffraction (EBSD) analyses showed presence of relatively more recrystallized grains and absence of fiber texture in Mg/B₄C nanocomposites when compared to pure Mg. The evaluation of mechanical properties indicated a significant improvement in tensile properties of the composites. The significant improvement in tensile ductility (∼180% increase with respect to pure Mg) is among the highest observed when compared to the pure Mg based nanocomposites existing in the current literature. The superior mechanical properties of the Mg/B₄C nanocomposites are attributed to the uniform distribution of the nanoparticles and the tendency for texture randomization (absence of fiber texture) achieved due to the nano-B₄C addition.     

Recycling of aluminium based metal matrix composite using disintegrated melt deposition technique

Abstract

In the present study, the feasibility of recycling a silicon carbide particulate reinforced aluminium composite was investigated. The composite was synthesised and recycled using an innovative disintegrated melt deposition tech nique. Microstructural characterisation studies revealed a marginal decrease in porosity, reinforcement content and size, no change in reinforcement distribution pattern, and improved interfacial integrity between matrix and reinforcement following recycling. Microhardness measurements revealed an increase in the hardness of the interfacial region in the recycled specimens. Results of physical and mechanical property characterisation revealed an increase in elastic modulus, 0·2% yield strength, ultimate tensile strength, and ductility, and a reduction in the coefficient of thermal expansion of the recycled specimens when compared with the parent composite. These properties were rationalised in terms of the microstructural characteristics associated with the disintegrated melt deposited composite specimens. Particular emphasis is placed on the study of the effect of recycling on the microstructure and properties of the composite.