EFFECT OF SOAKING TREATMENT ON THE MICROSTRUCTURE AND WEAR BEHAVIOR OF THE ULTRASONIC MELT-TREATED B390 HYPEREUTECTIC Al-Si ALLOY

摘要

The hypereutectic Al-Si alloys constitute an important family of alloys because of their excellent wear resistance and low thermal expansion. The current work aimed at studying the effect of soaking treatment on the microstructure and wear behavior of the ultrasonic melt-treated B-390 hypereutectic Al-Si alloy. The results showed that the ultrasonic treatment resulted in uniform distribution and refinement of the primary silicon particles. The soaking treatment resulted in coarsening of the primary silicon particles, with larger particles obtained at longer soaking times. It was also observed that particle coalescence is the primary ripening mechanism for the primary Si, especially in the ultrasonic-treated samples. The wear weight loss changed with the soaking time, with the ultrasonic-treated samples exhibiting more consistent trend with little variations of weight loss at different soaking times. The optimum particle size and distribution is obtained after 5 min. soaking of the conventionally cast samples, and 10 min. for the ultrasonic-treated samples. The worn surface of these conditions is characterized by fine and shallow wear scratches with little particle detachments. Soaking at high temperature leads to reducing the volume fraction of the primary silicon, which consequently, caused high weight losses during wear test.