Effect of pre-stretching on the precipitation evolution and mechanical properties of GW63K magnesium alloy

Abstract

The regulation of precipitates remains a critical issue in the advancement of high-strength magnesium-rare earth (Mg-RE) alloys. An effective method to manipulate the precipitates in Mg-RE alloy is through cold deformation before ageing. In this work, we investigated the impact of pre-deformation before artificial ageing on the microstructures and mechanical properties of GW63K alloy. The results reveal that, pre-stretching introduces <a> type dislocations which facilitate uniform nucleation in the matrix of 200 °C-aged alloys and non-uniform nucleation on the dislocations of 225 °C-aged alloys. Compared with the undeformed alloy after peak ageing treatment, pre-deformation increases the number density of β' precipitates with reduced average size. Semi-quantitative estimations show that precipitation strengthening and solid solution strengthening are the dominant contributors to strengthening in peak-aged alloys at temperatures of 200 and 225 °C respectively. Furthermore, pre-deformation not only introduces the dislocation strengthening of approximately 25 and 26 MPa, but also enhances the precipitation strengthening by 23 and 17 MPa at 200 and 225 °C peak-aged conditions, respectively.