Effect of Si Content on Turning Machinability of Al-Si Binary Alloy Castings

Abstract

The effect of eutectic Si or primary Si on the machinability of Al-Si alloy castings, where eutectic Si or primary Si was served to improve the chip breakability were investigated. To enhance chip breakability, eutectic Si made the chips thin, and cracks that formed in primary Si during machining acted as nuclei for chip breaking. Eutectic Si had a stronger effect on surface roughness than primary Si, and eutectic Si reduced the adhesion on the cutting edge. The decrease in adhesion on the cutting edge led to a corresponding decrease in surface roughness. The cracking of primary Si was responsible for the increase in surface roughness in hypereutectic alloys. Tool wear increased with increasing amount of eutectic Si. In hypereutectic alloys, tool wear was accelerated by the contact between the tool and cracked primary Si.