Dry wear and friction properties of δ-Al2O3 short fiber reinforced Al-Si (LM 13) alloy metal matrix composites

Planar-randomly oriented alumina shea fiber (Saffil) reinforced Al-Si (LM 13) alloy metal matrix composites (MMCs) were produced by a modified liquid infiltration technique. The wear and friction behavior of LM 13 alloys containing up to 30 vol % Al2O3 fiber were investigated in sliding against a hard steel counterface (63 HRC) by continuous loading experiments carried out in a pin-on-disk machine under dry conditions at room temperature in the transverse section of the composites. Sliding tests were conducted at five loads (5 N, 10 N, 20 N, 40 N and 60 N) and under a constant sliding speed of 1 m/s. The wear and coefficient of friction against sliding distance initially showed a short transient period and then reached a steady state behavior. The wear behavior of the composites was dependent on fiber volume and applied load. The wear rate decreased with increased volume fraction of fiber and increased with increasing load. The wear resistance of the composites over the range of loads and volume fraction of fibers studied was found to range from almost 1.2 to about 4.0 times that of unreinforced alloy. Coefficient of friction decreased with increased fiber volume percent and applied normal load. To analyze wear mechanisms, wear surfaces were examined by scanning electron microscopy and it was found that the wear of the unreinforced alloy and composites occurred by groove formation and its subsequent growth, the magnitude of which increased with increasing fiber volume and applied normal load. (C) 1998 Elsevier Science S.A.