Mechanisms of material removal during low stress and high stress abrasion of aluminum alloy-zircon particle composites

Abstract

(Al11.8Si4.0Mg alloy)-zircon particle composites containing zircon particle (size, 100 μm) volume fractions of 0.15 and 0.35 have been prepared by liquid metallurgy techniques. The low stress abrasion resistance of these composites was tested using a rubber wheel abrasion test apparatus with American Foundrymen's Society 50–70 mesh rounded quartz abrasive. Scratch tests were performed on metallographic surfaces of composites using a fixed-depth scratch test apparatus in order to simulate the high stress pin-on-drum abrasion test. The results show that the low stress abrasive wear rate of the aluminum alloy was decreased by a factor of 5 as a result of the dispersion of the 0.35 volume fraction of zircon particles. The wear rate of the composite containing a zircon particle volume fraction of zircon 0.35 (a Vickers hardness of 144 HV) under the low stress condition was found to be equal to that of normalized AISI 1045 steel (197 HV). Scanning electron microscopy micrographs of the composite surfaces abraded under low stress conditions show that the zircon particles stand proud of the matrix without any particle pull-out or interfacial debonding. Material removal mechanisms during low stress abrasion of the composites appear to be governed by microfracture of zircon particles, leading to subsequent pit formation. There is a direct correlation between material removal mechanisms during fixed-depth scratch testing and high stress pin-on-drum abrasion. In both cases there was catastrophic fragmentation of the zircon particles.