| It was known that the wear characteristics of hypereutectic Al-Si alloys are mainly affected by the size and the volume fraction of primary Si phases. However, the effects of the size and the volume fraction of primary Si phases on the wear characteristics was not yet clear. Thus these were investigated in this study, and the effect of Fe addition on the wear characteristics was also studied. The wear test was carried out with variations of load (30∼2OON) and sliding speed (0.2, 1, 2m/s) at a constant sliding distance(2000m) on a pin-on-disk type wear testing machine. As a result, the Al-20Si-5Fe alloy, which had the primary phases of medium size(20∼30㎛), had the highest wear-transition-load(200N at sliding speed of 1m/s). The reason was related to MML (Mechanically Mixed Layer). MML, which was formed on alloy`s worn surface, had the higher hardness than the matrix and played a role as solid-lubricants. Therefore it seemed that the MML protected the matrix from contacting with counterface and held back the thermal softening of matrix by inhibiting the temperature rising of the surface. The MML of Al-20Si-5Fe, which had primary phases of 20∼30㎛, had the highest hardness and inhibited most effectively the temperature rising of the surface. |
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