M. K. Khraisheh, Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates; F. K. Abu-Farha, University of Kentucky, Lexington, KY

Summary:

As the lightest constructional metal on earth, magnesium (and its alloys) offers a great potential for weight reduction in the transportation industry. Many automotive components have been already produced from different magnesium alloys, but they are mainly cast components. Production of magnesium outer body components is still hindered by the material’s inferior ductility at room temperature. Magnesium alloys are usually warm-formed to overcome this problem; however, it was found that magnesium exhibits superior ductility and superplastic-like behaviour at higher temperatures. More comprehensive database of magnesium’s high temperature behaviour is needed for broader utilization of the metal and its alloys. In this work, the deformation behaviour of Magnesium Alloy AZ31 is investigated under a wide range of forming temperatures (23 to 500°C) and true strain rates (2x10^-5 to 3x10^-2 s^-1). A discussion on the gripping and testing approach is presented to shed some light on the important and controversial issue of high temperature tensile testing. The results of the mechanical and microstructural tests are used to develop a microstructure-based constitutive model that can capture the behaviour of the material under the various forming conditions. The model is based on the viscoplasticity theory and includes a microstructure-based overstress function.