Effect of stir-casting on the microstructure and adhesive wear characteristics of cast Al—Si—Cu alloy

Abstract

This paper describes the microstructure, hardness, and wear characteristics of cast aluminium—silicon alloy produced by a stir-casting technique. A hypoeutectic (Al—7% Si—0.8% Cu) alloy was cast under different stirring speeds. The stirring of semi-solid metal (SSM) slurries was performed under continuous cooling conditions from liquidus temperature. Wear characteristics of the alloys under investigation were studied using a pin-on-flat wear system over a range of normal loads (10—40 N) at constant average sliding speed (0.2 m/s) against cast iron and stainless steel counter surfaces. Stir-casting resulted in a material with higher microhardness and lower wear rates than conventional cast alloy. Both the stir-cast and conventional cast alloy showed higher weight loss against the stainless steel compared with that against the cast iron counter surface. Optical microscopy of the conventional cast and stir-cast alloys showed that the stir-casting results in spheroidization and refinement of primary alpha aluminium and modification of eutectic silicon. The scanning electron microscopy of wear surfaces was carried out to investigate the mode of wear. Attempts were made to establish the structure property relationship.