Evaluation of castability of high pressure die cast magnesium based alloys

Alloy characteristics that impact on castability, such as hot tearing and fluidity, are as significant to the success of an alloy development program as the mechanical properties requirements of the final component. However, castability is often overlooked in the alloy development process and this could lead to substantial problems in fabrication. A new die has been developed to test multiple indicators of the high pressure die castability of an alloy. A rating system has been introduced to evaluate several exterior quality factors for high pressure die castings. This is coupled with selected metallographic inspection of the interior defects and the results are combined to compare the relative performance of different alloys. It was found that ZA124 alloy was the most castable of the alloys tested followed by AZ91 with the castability decreasing with decreasing Al content for Mg–Al based alloys.