Effects of rheo-die casting process on the microstructure and mechanical properties of AM50 magnesium alloy

摘要

AM50 Mg alloy is usually processed by high-pressure die casting (HPDC) for applications demanding high ductility. However, this alloy has a high tendency of hot tearing, and is difficult to cast because of its large freezing range and low final solidification temperature. In this investigation, the rheo-die casting (RDC) process, a new semi-solid processing technology developed by BCAST at Brunei University, was used to overcome such casting difficulties and to improve mechanical properties. It was found that the RDC AM50 alloy exhibited much improved mechanical properties, especially for the elongation, over those of the same alloy produced by HPDC and other semi-solid processing technologies. The improved mechanical properties can be attributed to the elimination of large gas pores as a result of gas entrapment, substantial reduction of hot tearing, and fine, uniform microstructure, as a consequence of solidification under high shear rate and high intensity of turbulence in the RDC process.