An aluminium Al-Si12Cu/TiB 2 metal matrix composite was fabricated using the liquid metallurgy route, and its dry sliding wear characteristics were investigated under various sliding parameters. The titanium diboride (TiB 2 ) particles (10 wt%, average size 50-60 lm) were incorporated into the matrix and its microstructural characteristic was examined. A five-level central composite design experiment was developed using response surface methodology; parameters such as load, velocity and sliding distance were varied in the range of 10-50 N, 1-5 m/s and 500-2500 m, respectively. Dry sliding wear tests were performed as per the experimental design using a pin-ondisc tribometer at room temperature. Significance tests, analyses of variance and confirmatory tests were performed to validate the developed model. Study of the microstructural characteristics revealed uniform dispersion of the reinforcement particles throughout the composite. The regression result showed that the developed model performed well in relating the wear process parameters with the response and predicting the wear behaviour of the composite. The surface plot showed that wear rate increased with increasing load at all velocities and distances, and decreased with increasing sliding distance. In the case of velocity, the wear rate decreased initially, increasing after the transition velocity had been reached. Scanning electron microscopy analysis revealed severe wear at a high load due to a higher level of deformation of the composite surface.

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Functionally graded MMCs and homogenous composites (Al/AlN and Al/SiO2-10 wt %) have been fabricated through centrifugal casting and liquid metallurgy route respectively. The properties of these composites were compared with aluminium alloy. Microstructural characteristics and hardness were studied on surfaces of functionally graded materials (FGMs), homogenous composites and unreinforced aluminium alloy using optical microscope and Vickers micro hardness tester respectively. Tensile test was carried out on outer and inner sections of FGMs and specimens from homogenous composites and alloy utilizing universal testing machine. Three body abrasive wear test was conducted for different loads and speeds to study their effect on Downloaded by [University of California Santa Barbara] at 05:25 25 June 20162 surfaces of composites and alloy using dry abrasion tester. Microstructural and hardness results reveal that outer surface of aluminium nitride (AlN) reinforced FGM has particle enriched region with highest hardness. Tensile strength was found higher in both homogenous composites compared to zones of their FGMs. Abrasion wear rate was found increased with increase in load and decreased with increase in speed. The outer surface of AlN reinforced FGM has higher wear resistance followed by outer surface of SiO2 reinforced FGM. Scanning Electron Microscopy analysis was performed on worn out surfaces and observed particle enriched outer surface of Al/AlN FGM with less abrasion.

Functionally graded Al–Si12Cu/10 wt.% B4Cp metal matrix composite (MMC) has been fabricated under stir casting process followed by horizontal centrifugal casting method. The casting of length 170 mm, outer diameter 160 mm, and thickness 16 mm was obtained under the centrifugal speed of 1000 rev min−1. The microstructural evaluation was carried out on the surfaces at distance of 3, 6, 9, and 11 mm from the outer periphery of the casting to ensure the distribution of reinforcement particles, and the surfaces at same distance were tested for its hardness using microhardness tester. The microstructural results revealed that surface at a distance of 3 mm from the outer periphery has reinforcement concentration of 32% and surface at a distance of 11 mm has reinforcement concentration of 3%. The hardness of the surface was improved considerably according to the reinforcement concentration. The three-body abrasive wear test was conducted on the composite specimens as per L16 orthogonal array for parameters such as the load, speed, time, and reinforcement concentration. Each parameter was varied for four levels and the optimum level of each parameter was found out through signal-to-noise ratio analysis using “smaller-the-better” characteristics. The signal-to-noise ratio analysis revealed that load was the dominant parameter on the abrasive wear behavior followed by reinforcement concentration, speed, and time. The analysis of variance (ANOVA) result indicates the parameter that affects the response significantly and results were agreed with signal-to-noise ratio analysis. The regression equation was developed and results were validated using confirmation experiments. The worn-out surfaces were examined using scanning electron microscope (SEM) for observing the wear mechanism.