Effect of squeezing on porosity and wear behaviour of partially remelted A319/20 vol% SiC p metal matrix composites

This article describes the effect of the squeezing process on the porosity of partially remelted A319/20 vol% SiC particulate (SiC_p) reinforced metal matrix composites (MMCs). The composite alloy was originally fabricated by a stir casting technique. The effect of squeezing process parameters such as the squeezing time, compressive stress, and the liquid weight fraction inside the melt on the overall porosity was extensively studied. Moreover, pin-on-disc wear tests were conducted to evaluate the effect of porosity on the wear resistance of the composites. It was found that the squeezed composites have lower overall porosity when compared with the as-cast composites. The lowest overall porosity content was observed when the squeezing process variables were at their peak values. After squeezing, the gas-bubble voids were practically eliminated, whereas the inter-particle voids were significantly reduced but not completely eliminated due to fracture of SiC_p and generation of new inter-particle microvoids. Wear test results showed that the wear resistance of the squeezed composites was significantly higher than the as-cast composites due to the lower porosity content of the squeezed composites. The wear resistance of the squeezed composites depends significantly on the overall porosity. It has been found that the wear rate of the squeezed composites increase with increasing overall porosity.