A super high-strength Mg-Gd-Y-Zn-Mn alloy fabricated by hot extrusion and strain aging

A super high-strength wrought Mg-12.6Gd-1.3Y-0.9Zn-0.5Mn (GWZ1311M, wt%) alloy fabricated by hot extrusion and strain aging is developed. The strain before aging including cold rolling or cold rolling plus stretching results in strong work hardening and promotes the precipitation of gamma' phase and chain-like structures during subsequent aging. While the grain sizes and texture components in different aged samples do not show essential difference, the number densities of both gamma' phase and chain-like structures are much higher in strain-aged samples than those in the aged sample without pre-deformation. The enhanced formation of gamma' phase and chain-like structures are associated with the higher dislocation density imparted by the cold deformation before aging. As a result, the GWZ1311M alloy after strain aging at 200 degrees C achieves super high tensile yield strength of 475 +/- 8 MPa (only applying cold rolling before aging) and 543 +/- 1 MPa (applying cold rolling plus stretching before aging), respectively. In contrast, the yield strength of peak-aged GWZ1311M alloy is only 410 +/- 6 MPa after conventional aging at 200 degrees C. It is proposed herein that hot extrusion and strain aging, especially applying cold rolling plus stretching before aging, is an effective approach for developing high-strength Mg alloys. (C) 2019 Published by Elsevier Ltd.