Tribology of aluminum-based metal matrix composites: Fundamental study of wear behavior as influenced by microstructure

Rolling and sliding wear experiments were conducted on selected aluminum-based metal-matrix composites against hard iron base counterfaces. Wear morphology and surface chemistry in these composites after tribo-contact have been characterized using a variety of analytical techniques to increase understanding of wear mechanisms. Different wear behavior for rolling and sliding wear, which have different temporal contact stress state, has been investigated considering the phases, their interface and microstructure, and the role of heat treatment.; Results for sliding wear of 2124-SiC whisker MMC indicate a much higher wear rate when dry than when lubricated. SEM/EDX and TEM analyses show direct evidence of adhesive wear through plastic deformation for dry sliding and abrasive wear through plowing and polishing for lubricated sliding. A chemical wear mechanism was observed and characterized for lubricated sliding of 2014-Al{dollar}sb2{dollar}O{dollar}sb3{dollar} particle MMC. Chemical reaction between Al{dollar}sb2{dollar}O{dollar}sb3{dollar} particles and the steel mating surface gives a layer of oxides which results in no weight loss after the run-in period, however, a deeper wear scar on the mating material results. The rolling wear mechanisms in cast MMCs are particle pull-out and severe matrix pitting due to the interaction between microcracks and the ceramic-metal interfaces.; The influence of microstructural changes on the wear behavior of metal-matrix composites was investigated in powder metallurgy 2124-SiC particle MMCs with different sizes of SiC particles and matrix heat treatments. The wear results for lubricated rolling and sliding reveal a similar correlation with particle size in that wear resistance decreases with particle size. With respect to heat treatment, the specific wear rate for sliding increases with aging and overaging gives the best wear resistance. This is attributed to less pull-out of the SiC particles due to a change of the fracture path. The rolling wear resistance on the other hand is maximum for the underaged condition. Since wear of a steel mating material against a ceramic dispersoid MMC occurs primarily by third-body wear, decrease in pull-out of a ceramic phase by controlling the MMC microstructure significantly reduces the damage to the mating surface.