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 ofrnalloys because of their excellent wear resistance and low thermalrnexpansion. The current work aimed at studying the effect ofrnsoaking treatment on the microstructure and wear behavior of thernultrasonic melt-treated B-390 hypereutectic Al-Si alloy. Thernresults showed that the ultrasonic treatment resulted in uniformrndistribution and refinement of the primary silicon particles. Thernsoaking treatment resulted in coarsening of the primary siliconrnparticles, with larger particles obtained at longer soaking times. Itrnwas also observed that particle coalescence is the primaryrnripening mechanism for the primary Si, especially in thernultrasonic-treated samples. The wear weight loss changed with thernsoaking time, with the ultrasonic-treated samples exhibiting morernconsistent trend with little variations of weight loss at differentrnsoaking times. The optimum particle size and distribution isrnobtained after 5 min. soaking of the conventionally cast samples,rnand 10 min. for the ultrasonic-treated samples. The worn surfacernof these conditions is characterized by fine and shallow wearrnscratches with little particle detachments. Soaking at highrntemperature leads to reducing the volume fraction of the primaryrnsilicon, which consequently, caused high weight losses duringrnwear test.