Effect of high ratio of reinforcement particle size to matrix powder size and volume fraction on microstructure, densification and tribological properties of SiCp reinforced metal matrix composites manufactured via hot pressing method

Abstract

The effects of reinforcement particle to matrix powder size ratio (Rs/Ms) and volume fraction of reinforcement particle on the microstructure, densification and tribological properties of SiCp reinforced aluminium (Al–SiCp) metal matrix composites manufactured via hot-pressing method were investigated for high ratios of Rs/Ms (1≤Rs/Ms≤4). Central composite design (CCD) method was used for experimental design. Based on the results obtained in this study, density of 99% could be reached and a uniformly distribution of reinforcement particles in microstructure could be observed for the composite with the volume fraction of 15% and Rs/Ms ratio of 3.5. Also, the relative density increased as Rs/Ms ratio increased up to the reinforcement volume fraction of 17.5%. However, an increase in Rs/Ms ratio had an unfavourable effect on the density at the high volume fractions (≥17.5). Results also showed that there was no direct correlation between hardness and wear resistance as a function of volume fraction and Rs/Ms ratio. The wear tests were performed under adhesive wear condition using pin-on-ring test machine. The results showed that Rs/Ms ratio had a strong influence on the microstructure and wear behaviour of Al–SiCp composites. Up to the volume fraction of 15%, as the reinforcement particle size or reinforcement particle to matrix powder size ratio increased, the wear loss decreased; however, at the volume fractions higher than 17.5%, wear loss increased with increasing the reinforcement particle to matrix powder size ratio. Both adhesive and abrasive wear mechanisms were the dominant failure mechanisms at the low volume fractions (≤15%) while delamination wear was the most dominant failure mechanism for the composites with higher volume fractions (≥20%).