Microstructure and surface characterization of copper and zinc added heat treated stir cast A356 alloy

The aim of this work is to investigate the variations in microstructure, hardness, wear and surface roughness between as-cast and heat treated trace elements added A356 alloy. Alloy A was prepared by adding 1 wt.% magnesium to A356 alloy which was used as the base material for the preparation of alloys with zinc (Zn) and copper (Cu) particles as alloying elements. Other set of samples was fabricated where Cu-coated Zn and Cu were added as reinforcements to base matrix A. The microstructural analysis indicated that the addition of Zn to A356 as an alloying element had a limited effect on controlling the grain size during solidification compared to Cu. The addition of Cu as reinforcement resulted in a higher proportion of pro eutectic α-Al phase, leading to finer grain boundaries. Micro-polishing test was conducted on the alloys and composites by determining the surface roughness (Ra) value using profilometer to study the changes in surface roughness under individual load conditions of 20 and 40 N. In the as-cast condition, the addition of Cu increased the hardness by 39% and 58% over the base alloy, respectively. Age-hardening treatment significantly enhanced the wear resistance properties of unreinforced alloys and composites at both aging temperatures, especially at 100 °C. Composite samples exhibited excellent surface finish (lower surface roughness) compared to alloy samples, attributed to the presence of hard reinforcement particles.