ABRASION-INDUCED MICROSTRUCTURAL CHANGES AND MATERIAL REMOVAL MECHANISMS IN SQUEEZE-CAST ALUMINUM-ALLOY SILICON-CARBIDE COMPOSITES

An attempt has been made to understand wear-induced subsurface microstructural changes and material removal mechanisms in squeeze-cast BS LM11 alloy dispersed with 10 vol % SiC. Particles as well as fibres of SiC were separately dispersed in the alloy matrix to determine the influence of shape of the dispersoid on the abrasion behaviour of the latter. Abrasion tests were conducted on a standard rubber wheel abrasion test apparatus. Silica sand was used as the abrasive medium. Abrasive wear rates of the specimens were found to decrease gradually with the number of test intervals until a steady state value was attained. This was attributed to the protrusion of the reinforcement phase and abrasion-induced work hardening of the matrix in regions close to the abraded surface. The dispersoid/matrix interface as well as the shape of the dispersoid was found to influence the abrasion rate of the composites. A poor dispersoid/matrix interface led to higher rate of abrasion due to pull-out of the dispersoid. On the other hand, good bonding between the dispersoid and the matrix helped the dispersoid phase to be retained by the matrix, offering reduced rate of abrasion.