Mass reduction for automotive components has become one of the key approaches for greenhouse gas emission reduction of the automotive industry [1] . Materials selection, tooling design, and processing parameters are the three crucial pillars for achieving mass reduction in automotive castings [2] . Gravity casting and low pressure die casting processes have a relatively longer cycle time, and hence higher manufacturing cost for high volume production. Traditional high pressure die casting (HPDC) process has a much shorter cycle time, which is suitable for scaled production in the automotive industry [3] . However, some casting defects, such as gas porosities and shrinkage porosities in HPDC components, cannot be