Mechanical and tribological behaviour of tungsten carbide reinforced aluminum LM4 matrix composites

Aluminum-based metal matrix composites (AMCs) play a vital role for potential applications in aerospace and automotive industries. This paper explores the experimental analysis of a composite with aluminum LM4 alloy as the matrix and tungsten carbide (WC) as the reinforcement material. The composite specimens were fabricated by the stir casting process. The reinforced ratios of 5, 10 and 15?wt.% of WC particulates were stirred in molten aluminum LM4 alloy (AALM4). Once the composite is solidified, the specimens are prepared to the required ASTM dimensions and tested for various mechanical properties such as tensile strength, impact strength and hardness. Moreover, the tribological behavior of the composite was studied using the pin-on-disc wear test apparatus. X-ray diffraction (XRD) analysis was conducted to analyze the various elements present in the composites. Finally, the scanning electron microscope (SEM) analysis reveals the uniform distribution of WC particles in Aluminum LM4 alloy matrix. The improvement in mechanical properties – hardness, impact strength and tensile strength – was achieved for the increase in the addition of wt.% of WC particles in the LM4 matrix. The decrease in mass loss was observed for the composite containing 15?wt.% of WC during the wear test among the various composites tested.     

Investigation of microstructure and wear behaviors of al matrix composites reinforced by carbon nanotube

In this study, the effect of CNT amount in Al-CNT composites produced by adding carbon nanotube (CNT) to 7075 Al alloy in various amounts on microstructure and wear behaviors of aluminum matrix composites was investigated. CNT was added to 7075 Al alloy powder at five different amounts. The powders were mechanically milled for 2 hours. Mechanical milled powders were cold pressed and then pre-shaped by hot pressing. Pre-shaped samples were sintered for 1 hour under 10^?6 millibar in 580°C. Microstructure examinations, hardness measurements, and wear tests were carried out. The results show that CNT's in the microstructure were agglomerated as nanotube amount increases and there was no uniform distribution. The highest hardness value was obtained in AMC reinforced with 1% CNT while it is seen that hardness of the composite decreases and weight loss increases as CNT amount increases.     

Microstructure and mechanical behaviour of aluminium matrix composites reinforced with graphene oxide and carbon nanotubes

Aluminium (Al) matrix composites reinforced with either 0.5 wt% graphene oxide (GO) or 0.5 wt% carbon nanotubes (CNTs) were hot extruded from ball-milled powders. A control, pure Al bar was also fabricated. Microstructural examination, including Raman mapping, showed a relatively poor dispersion of the carbon nanomaterials within the Al matrix, particularly in the case of the CNTs. Consequently, while the mean grain size of the Al matrix remains invariant with the addition of CNTs, the Al/GO composite exhibits reduced grain size compared to pure Al due to the pinning effect of the reinforcement. Moreover, the addition of both carbonaceous materials resulted in a slight decrease in the typical extrusion duplex <111> + <100> fibre texture intensity. This weakening of the texture was more pronounced in the Al/GO composite, partly due to the pinning effect of the reinforcement. In agreement with their relative mean grain sizes, the Al/GO composite shows an improved mechanical performance over pure Al. Despite the similarity of the mean grain sizes, the Al/CNT composite displays comparable hardness and a decreased compressive yield stress relative to the pure Al. In the absence of chemical reactions at the interfaces, this was attributed to a low efficiency of load transfer from the Al matrix to the reinforcement resulting from the large extent of agglomeration of CNTs.     

Production and properties of SiCp-reinforced aluminium alloy composites

A vacuum infiltration process was developed to produce aluminium alloy composites containing various volume fractions of ceramic particles. The matrix composites of aluminium with 9.42 wt%Si and 0.36 wt%Mg containing up to 55 vol% SiCp were successfully infiltrated and the effect of infiltration temperature and volume fraction of particle on infiltration behaviour was investigated. In addition to aluminium powder, magnesium was used to improve the wetting of SiC particles by the molten aluminium alloy. The infiltration rate increased with increasing infiltration time, temperature and volume fraction of particle, but full infiltration appeared at the optimum process parameters for the various volumes of fraction composite compacts. In addition, the microstructure, hardness, density, porosity and wear resistance of the composites were also examined. It is observed that the distribution of SiC particles was uniform. The hardness and density of the composite increased with increasing reinforcement volume fraction and porosity decreased with increasing particle content. Moreover, the wear rate of the composite increased with increasing load and decreased with increasing particle content.     

Fabrication of TiB2 particulate reinforced magnesium matrix composites by powder metallurgy

Magnesium metal matrix composites (MMCs) reinforced with 10, 20 and 30 vol.% TiB₂ particulates, respectively, were fabricated by powder metallurgy. The microstructure, porosity, hardness and abrasive wear behavior of the composites were evaluated. Microstructural characterization of Mg MMCs showed generally uniform reinforcement distribution. As compared with pure Mg, the hardness (HB) values of Mg MMCs reinforced with 10, 20 and 30 vol.% TiB₂ particulates were increased by 41%, 106% and 181%, respectively. The abrasive wear tests showed that the wear resistance of Mg MMCs is increased with the increasing of the reinforcement volume fraction. This was due to the strong particulate-matrix bonding and high hardness of the TiB₂ particulate.     

Wettability Enhancement of SiCp in Cast A356/SiCp Composite Using Semisolid Process

The effects of SiCp treatment and magnesium addition on microstructural and mechanical properties of Al356/20 wt% SiCp semisolid composites were investigated. The results showed that cleaning and oxidizing of SiCp and addition of 1 wt% Mg resulted in improving wettability, incorporation, and uniform distribution of SiCp in A356 matrix. Consequently, the ultimate tensile strength (UTS) value increased by 19% and 32% when the SiC was treated and also when Mg was added, respectively, compared to as-received SiCp. In addition, hardness value increased from 69.7 HV in as-received SiCp to 94.8 HV after SiCp treatment and addition of Mg.     

Effect of SiC content on the processing, compaction behavior, and properties of Al6061/SiC/Gr hybrid composites

Aluminum matrix composites reinforced with SiC and graphite (Gr) particles are a unique class of advanced engineered materials that have been developed to use in tribological applications. The conventional techniques for producing these composites have some drawbacks. In this study, a new method, namely In situ Powder Metallurgy (IPM), is applied for the preparation of Al6061/SiC/Gr hybrid composites. In this method, the stir casting and the powder metallurgy synthesizing processes are combined into an integrated net shape forming process. 0?C40 vol.% of SiC particles with an average size of 19 ??m, along with 9 vol.% of uncoated Gr particles, were introduced to the molten 6061 aluminum alloy. Then, the slurries were stirred in a specified time?Ctemperature regime resulting in mixtures of the SiC, Gr, and aluminum powder particles. The powder mixtures were cold pressed in six different pressures (between 250 and 750 MPa) and sintered. Finally, the produced composites were heat treated and their hardness and wear properties were investigated. Homogenous distribution of the SiC and Gr particles within the powder mixtures and the hybrid composites is clear from the SEM images. The results also show that the SiC particles decrease the compressibility of the hybrid powders and improve the hardness of composites. The best wear resistance is achieved in the hybrid composite containing 20 vol.% SiC particles.     

Heat treatment and wear characteristics of Al/SiCp composites fabricated by duplex process

This study was undertaken to investigate the effects of alloying elements and heat treatment on the microstructures, wear resistance, and heat resistance of Al–Si–Cu–Mg–(Ni)/SiC_p composites fabricated by a duplex process that consists of squeeze infiltration (1st step) followed by squeeze casting (2nd step). This duplex process produces a homogeneous distribution of SiC_p in Al alloy. The hardness of the composites increased with decrease in SiC_p size, and also with Ni addition in both the as-cast and the as-aged specimens. Compared with 5 and 10 μm SiC_p reinforced Al composites, the aging time to obtain the peak hardness was shortened for 3 μm SiC_p reinforced Al composite, because of higher density dislocations on the periphery of SiC_p in the matrix. However, the Al composite reinforced with 10 μm SiC_p was found to have the lowest wear amount as compared with 3 and 5 μm SiC_p composites. The amount of wear in Al/SiC_p composites decreased with increase of the sliding speed because abrasive wear occurred under low sliding speed and block-type wear debris occurred under high sliding speed.     

微波烧结原位合成TiC增强钛复合材料的性能

以纳米管(MWCNTs)和纯钛为原料,用微波烧结法原位合成TiC增强钛基复合材料,研究了这种材料的组织和性能并探讨了TiC增强相的生成机理.结果 表明,微波烧结时MWCNTs与Ti原位生成TiC增强相.MWCNTs的添加量(质量分数,下同)低于1％时TiC呈现颗粒状且分布均匀,Ti基体致密;MWCNTs的添加量高于1....     

Nano-sized aluminum oxide reinforced commercial casting A356 alloy matrix: Evaluation of hardness,wear resistance and compressive strength focusing on particle distribution in aluminum matrix

Achieving a uniform distribution of reinforcement within the matrix is a challenge which impacts directly on the properties and quality of the composite material. In the present study a fabrication and evaluation approach was used focusing on particle distribution in metal matrix. Al and Cu powders were separately milled with nano-Al₂O₃ particles and incorporated into A356 alloy via vortex method to produce cylindrical A356/nano-Al₂O₃ composites. The stirring was carried out in various durations. The variations of density, hardness, compressive strength, and wear resistance were measured throughout the cylindrical samples. The evaluation of mechanical properties and microstructural studies showed that an increase in stirring time led to a more uniform dispersion of particles in the matrix and also led to a decrease in mechanical properties due to an increase in porosity content of the composites compared with those of the samples stirred for shorter durations. Moreover, milling process affected particle distribution. Nanoparticles more uniformly dispersed in the Al₂O₃–Cu reinforced samples compared with that of the samples reinforced with Al₂O₃–Al or pure alumina powders.     

CHA/ UHMWPE复合关节材料的生物摩擦学研究

采用热压成型工艺制备了超高分子量聚乙烯 (U HMWPE) /珊瑚羟基磷灰石 (CHA) 复合关节材料 , 利用人工髋关节模拟磨损试验系统 , 研究了该类复合材料与 CoCrMo 合金组合关节在小牛关节液润滑条件下的摩擦磨损性能。实验结果表明 , 添加 CHA 能有效提高 U HMWPE关节材料的表面硬度 , 降低其磨损率。当CHA添加量为 20 wt %时 , 可获得表面硬度与抗磨损性能的良好匹配。小牛关节液润滑条件下 , U HMWPE及其复合材料的磨损机理主要表现为研磨磨损和疲劳磨损 , 磨损颗粒尺寸随 CHA粉体添加量的增加而增大。      

Mechanical properties of hot pressed SiCp and B4Cp/Alumix 123 composites alloyed with minor Zr

In the present study, effect of Zr addition on the microstructure and wear behavior of aluminum alloy composites (AMCs) reinforced with B4Cp and SiCp particles fabricated via hot pressing were investigated. The samples for the study composed of unreinforced aluminum alloy (Alumix 123) and the composites reinforced with 10% B4Cp and % SiCp were prepared by hot isostatic pressing (HIP) method. Similarly, all the samples alloyed with 0.2% Zr were also produced in order to make a comparison. The produced samples were evaluated for microstructural properties and mechanical tests for hardness, tensile and bending strength were performed. Wear test was carried out at 5 mm/s sliding speed under 3.0 N load for the all kind of hot pressed produced samples. The hot pressed composite microstructures have a more uniform distribution of the reinforcements. After HIP process, the composites were successfully produced with high density (>99%). The addition of Zr increased the yield and tensile strength of the samples. The highest strength value was found for the sample Al 123 matrix alloy with Zr. Evaluation of microstructures showed that copper and zirconium dispersed equally within the matrix microstructure without agglomeration. For the composite samples, Al3Zr, appeared as white precipitate, were inspected around B4C and SiC particles. The composite containing SiC particles and Zr had wear resistance value superior to those of the other counterparts.     

Microstructure and abrasive wear behaviour of B<Subscript>4</Subscript>C particle reinforced 2014 Al matrix composites

In this study, the microstructure and abrasive wear properties of varying volume fraction of particles up to 12% B₄C particle reinforced 2014 aluminium alloy metal matrix composites produced by stircasting method was investigated. The density, porosity and hardness of composites were also examined. Wear behaviour of B₄C particle reinforced aluminium alloy composites was investigated by a block-on-disc abrasion test apparatus where the samples slid against the abrasive suspension mixture (contained 10 vol.% SiC particles and 90 vol.% oil) at room conditions. Wear tests performed under 92 N against the abrasive suspension mixture with a novel three body abrasive. For wear behaviour, the volume loss and specific rate of the samples have been measured and the effects of sliding time and the content of B₄C particles on the abrasive wear properties of the composites have been evaluated. The dominant wear mechanisms were identified using SEM. Microscopic observation of the microstructures revealed that dispersion of B₄C particles was generally uniform while increasing volume fraction led to agglomeration of the particles and porosity. The density of the composite decreased with increasing reinforcement volume fraction but the porosity and hardness increased with increasing particle content. Moreover, the specific wear rate of composite decreased with increasing particle volume fraction. The wear resistance of the composite was found to be considerably higher than that of the matrix alloy and increased with increasing particle content.     

超声制备SiCp增强铝硅合金复合材料的磨损性能研究

研究使用功率超声制备SiCp颗粒增强铝基复合材料的新方法,并对所制得不同粒度SiCp的复合材料进行了组织分析和磨损性能的测试。实验结果表明,利用功率超声可以制备出颗粒在基体中均匀分布的复合材料,可增加SiCp的复合量,使SiCp与基体间润湿性良好。小粒度的SiCp颗粒增强复合材料较大尺寸的复合材料的耐磨性要好。     

Investigations on the effect of friction stir processing on Cu-BN surface composites

The main aim of this investigation focuses on fabrication of copper surface composites through friction stir processing (FSP) reinforced with boron nitride (BN) particles of varying volume fractions (5%, 10%, and 15%). Surface composites developed through single pass FSP were characterized for its microstructural, mechanical and tribological properties. Microstructural characterization indicated that developed surface composites were of good quality with reduced grain size and the SEM characterization confirmed good bonding between copper matrix and BN with uniform dispersion. Micro hardness survey of the developed surface composites showcased minimal deviation in the stir zone with increased trend in respect to the volume fraction of BN. The ultimate tensile strength, yield strength and percent elongation of FSPed composites was found to have reduced when compared with that of pure copper. BN dispersion in surface composite was effective in reducing the ductility and so maximum volume percent (15%) of BN dispersed composite prompt to have higher strength. The wear rate and friction coefficient of the developed surface composite was found decreasing with respect to increase in the dispersion of BN. Amongst the FSPed copper surface composite, specimen with 15?vol% of BN has shown the least wear rate with low coefficient of friction.     

Synergistic effects of TiC and graphene on the microstructure and tribological properties of Al2024 matrix composites

Al matrix composites have attracted significant attention of researchers in recent years due to their lightweight, excellent mechanical and tribological properties. In this study, an Al2024 matrix hybrid composite (AMHC) reinforced with both TiC nanoparticles and graphene nanoplatelets (GNPs) was produced via a route of powder metallurgy. And its microstructure, microhardness and tribological properties are compared with those of unreinforced Al2024 alloy matrix and Al2024 matrix composites reinforced with either only TiC or GNPs. It was found that the distribution of Al₂Cu, TiC nanoparticles and GNPs in the matrix and the wear resistance are significantly improved when introducing both TiC nanoparticles and the GNPs. The wear mechanisms change from the adhesion-dominant wear for Al2024 and the other singly reinforced composites into abrasive-dominant wear for the hybrid composite. The significantly improved wear resistance of the AMHC is attributed to the synergistic effects of reinforcing and self-lubricating of the TiC and GNPs.     

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.     

Machining characteristics,wear and corrosion behavior of AZ91 magnesium alloy - fly ash composites produced by friction stir processing

In the present work, fine grained AZ91 magnesium alloy – fly ash composite has been successfully fabricated by friction stir processing. Microhardness measurements show marginally higher hardness with uniform distribution compared with the base material. No significant difference in the mean cutting force was observed during drilling of the base metal and the composite. However, lower cutting forces were recorded in the sub-surface region of the composites. Interestingly, decreased corrosion resistance was noticed for the composite compared with the base material. Lower mass loss has been observed for the composite during reciprocating wear experiments. The results strongly suggest that the surface composite of AZ91 magnesium alloy – fly ash exhibits better mechanical and wear properties. However, decreased corrosion resistance is a significant observation that warns the applicability of these composites in corroding environment.     

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.     

Friction and wear behavior of carbon fiber reinforced brake materials

A new composite brake material was fabricated with metallic powders, barium sulphate and modified phenolic resin as the matrix and carbon fiber as the reinforced material. The friction, wear and fade characteristics of this composite were determined using a D-MS friction material testing machine. The surface structure of carbon fiber reinforced friction materials was analyzed by scanning electronic microscopy (SEM). Glass fiberreinforced and asbestos fiber-reinforced composites with the same matrix were also fabricated for comparison. The carbon fiber-reinforced friction materials (CFRFM) shows lower wear rate than those of glass fiber- and asbestos fiber-reinforced composites in the temperature range of 100°C-300°C. It is interesting that the frictional coefficient of the carbon fiber-reinforced friction materials increases as frictional temperature increases from 100°C to 300°C, while the frictional coefficients of the other two composites decrease during the increasing temperatures. Based on the SEM observation, the wear mechanism of CFRFM at low temperatures included fiber thinning and pull-out. At high temperature, the phenolic matrix was degraded and more pull-out enhanced fiber was demonstrated. The properties of carbon fiber may be the main reason that the CFRFM possess excellent tribological performances.