On the comparative manufacturing of full-size magnesium alloy automotive wheels by thixomolding and low-pressure die casting

For more than two decades, researchers have worked to manufacture magnesium alloy automotive wheels by low-pressure die casting (LPDC). However, large-scale application has been limited by insufficient mechanical strength and by defects that are difficult to control in safety-critical wheel components. Thixomolding can improve mechanical properties and suppress forming defects, but previous studies have mainly focused on specimens or small-to-medium-sized components. Here, thixomolding was applied to full-size magnesium alloy wheel manufacturing, and the world’s first batch of 16-inch thixomolded magnesium alloy automotive wheels was fabricated using a 3600-ton thixomolding machine. Four magnesium alloys were successfully formed into wheels in this study; but three of them cannot be disclosed at this stage for commercial reasons, this paper reports the detailed comparison between thixomolded and LPDC AE81M wheels. The results show that, compared with LPDC, thixomolding improved strength, ductility and tensile-property stability, which was associated with refined near-equiaxed α-Mg grains, a more continuous second-phase network, and reduced pores and oxide defects. This study demonstrates the feasibility of manufacturing full-size magnesium alloy automotive wheels by thixomolding and provides experimental support for developing lightweight magnesium alloy wheels with improved performance and reliability.