Effect of pre/post T6 heat treatment on the mechanical properties of laser welded SSM cast A356 aluminium alloy

Aluminium alloy A356 was treated by the Rheo semi solid metal (SSM) process, developed recently by CSIR-Pretoria, and cast in plates using a high pressure die casting (HPDC) machine. Plates in as cast condition (F) and heat treated T6 condition (pre HT) were butt welded, using an Nd:YAG laser. In another experiment, as cast welded samples were heat treated to T6 condition (post HT). The base metal and weld microstructures were presented. The effect of heat treatments on microstructure and mechanical properties of the welds was investigated. It was found that the fine dendrite structure of the weld metal contributed to the mechanical properties of the joint. The mechanical properties of the post HT samples were found to be higher than the pre HT and as cast materials.