An Investigation on Si Refinement Mechanism of Hypereutectic Al-Si via Applying Ultrasonic Vibrations

Abstract

Hypereutectic Al-Si alloys possess high abrasion resistance and low thermal coefficient which make them attractive for certain applications like as automotive industry. However, their ductility is affected by large Si particles size and therefore poor mechanical properties. The effect of ultrasonic treatment time on a hypereutectic Al-17% Si was evaluated. The results suggest vibration shock waves would refine the Si primary particles effectively. The refinement mechanism is initiated by creating holes inside the primary Si particle where the complete refinement is acquired within 30 s of ultrasonic vibrations. Another mechanism could be the collision of hard particles like as intermetallic particles to primary Si due to suitable agitation along with strong convection force that could lead to further Si particles fragmentation and refinement. The mechanical properties of the treated samples improved significantly in comparison with the non-treated ones. Better distribution of the primary silicon particles and their refinement could overcome the poor deformation of the Alloy.