Enabling Wider Use of Magnesium Alloys for Lightweight Applications by Improving the Formability by Groove Pressing

In the last decade or so, severe plastic deformation (SPD) has been shown to be an effective means for the production of fine grained microstructure in magnesium alloys at relatively low temperatures while altering the material texture to improve its formability. SPD of sheet geometry is particularly attractive in order to encourage wider use of magnesium alloys for lightweight applications. In this study, the microstructure evolution of magnesium alloy AZ31 sheet in the groove pressing process was examined at different processing conditions. The average grain size of the material was reduced from 13.3 μm to 1.9 μm after 4 cycles of deformation under the condition of progressive decreasing temperature and specimen rotation between cycles. The final microstructure was observed to be homogenous in both the transverse and rolling directions consisting of fine grains of 0.6-1 μm and a small fraction of coarser grains of 3-5 μm. The average hardness of the material was increased from 62 to 91 Hv with a uniform distribution along the thickness direction. This study has demonstrated that groove pressing is a highly effective method for production of fine grained microstructures in magnesium sheet using the technique of progressive decreasing temperature while alternate specimen rotation is necessary to prevent premature failure of the material.