EFFECT OF HEAT TREATMENT ON FRICTION AND WEAR BEHAVIOR OF A1-6061 COMPOSITE REINFORCED WITH 10% SUBMICRON A1_2O_3 PARTICLES

摘要

The present research aims at investigating experimentally the effect of heat treatment on the hardness, wear behavior, and friction properties of 6061 Al composite reinforced with sub-micron A1_2O_3 (10% vol.) produced by powder metallurgy. Heat treatment of the as-received composite starts by the solution treatment at a temperature of 550℃ for a period of two hours followed by quenching in chilled water and then age hardening at 175℃ for different periods. It is illustrated that heat treatment has relatively small effect on the hardness of the composite. This can be attributed to the large interface areas between the matrix and the sub-micron alumina in the composite, which reduces the whole concentration of vacancies in the matrix. The result is reduced efficiency of age hardening. For this reason, wear and friction tests were limited to the heat treated composite with four hours aging only. A pin-on-disc tribometer was used to conduct wear and friction tests against AISI 4140 at room temperature for both as-received composite and heat treated composite (with four hours of aging) for comparison. Wear tests indicate that heat treatment has the advantage of increasing transition load to severe wear by 30% compared to as-received composite. On the other hand, at high loads heat treatment results in larger delaminated flakes on the worn surface, indicating reduced fracture toughness. This, in turn, resulted in higher wear rates compared to the as-received composite. Dry friction coefficient is practically unaffected by the heat treatment.