Effects of processing parameters on microstructure and mechanical properties of powder-thixoforged 6061 aluminum alloy

A new processing technology, powder thixoforming, for preparation of particle reinforced metal matrix composites was proposed and 6061 aluminum alloy was prepared by powder thixoforging. 6061 ingots were first prepared by cold-pressing the atomized 6061 alloy powders, and then the ingots were partially remelted followed by thixoforging. The effects of reheating time, mould temperature and reheating temperature on microstructure and mechanical properties of the thixoforged alloys were investigated. The results indicate that all of the three parameters have large effects on the microstructure and mechanical properties. Owing to the microstructure changes, the fracture regime varies with the processing parameters. Furthermore, cracks always initiate from shrinkage porosities and inclusions, and then propagate either along the secondarily solidified structures or primary particles. The ultimate tensile strength, elongation and hardness of the resulting alloy are up to 196 MPa, 11.0% and HV 55.7 respectively.