Evaluation of Thixomolded, Magnesium Alloy Components for Structural Automotive Applications

Automotive manufacturers are continually pushing for reduced cost, increased fuel economy, lower emissions and improved performance. Magnesium is the lightest structural metal and has therefore enjoyed a double-digit annual growth in automotive applications since 1990, aimed at reducing vehicle platform weights to increase fuel economy. Nevertheless the progress of magnesium as an alternative lightweight structural material (compared to aluminum, engineered plastics and high alloy steels) is being impeded by the lack of published alloy properties and general knowledge of the material. Thixomat, Inc. is conducting independent fundamental studies to measure the influence of Thixomolding® process parameters on a variety of physical and mechanical properties for injection molded magnesium alloys. Determination of conventional mechanical properties are being complemented with fatigue behavior studies using new ultrasonic fatigue instrumentation at the University of Michigan. Additional studies on high temperature properties (bolt load retention studies as well as conventional creep elongation measurements) are also being performed on both conventional alloys and the new high temperature alloys being developed by primary magnesium producers. The results of current studies confirm that the Thixomolding® process is a viable alternative manufacturing process for producing structural automotive components. Recommendations for future focused development activities and improvements in process economics are also presented.