Evolution of primary Si phase, surface roughness and mechanical properties of hypereutectic Al–Si alloys with different Si contents and cooling rates

Abstract

ABSTRACT The solidification behaviour of hypereutectic Al–Si alloy melts at 70°C above the liquidus with different Si contents between 27 and 50 wt% and cooling rates from 50 to 300°C/min were studied using a confocal laser scanning microscope (CLSM). It was found that the primary Si size and surface roughness decreased while the wear resistance improved with higher cooling rates and lower Si contents. An interesting result showed that the hardness and wear resistance changed in an opposite direction with increase of Si content. The causes of the improvement of wear resistance are mainly attributed to a decreasing primary Si size and the corresponding surface roughness.