INVESTIGATION OF DISTINCTIVE SOLUTIONIZING PROCESS PARAMETERS ON SIGNIFICANTLY INCREASING IN STRENGTH AND DUCTILITY OF As-CAST AZ80 Mg ALLOY

A distinctive solutionizing process parameter was developed and performed to significantly enhance strength and ductility of aged AZ80 Mg alloy.  The microstructure-processing-properties relationship was studied to help elucidate the mechanism.  Microstructure and mechanical properties were studied by using optical microscopy, Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray diffraction, hardness and tensile testing.  The results show that the solutionization at 380°C/10h followed by 420°C/10h promoted significant dissolution of eutectic Mg17Al12 and intermetallic phases.  After standard aging at 200°C/10h, the formation of high-density precipitates Mg17Al12 with more spheroidization precipitates and lesser discontinuous precipitates morphology, which was not observed in conventional heat treatment for aged AZ80 Mg alloy.  Fine precipitates Mg17Al12 resulted in a significant increase in ultimate tensile strength (50.3%), yield strength (35%), elongation (106%) and hardness (40%) compared to conventional heat treated cast AZ80 Mg alloy.  These properties are comparable to the commonly used aerospace grade cast aluminium alloy A356.