Improvement of strength of Mg-12Gd-3Y-0.5Zr alloys processed by combination of ECAP and Extrusion

摘要

Equal channel angular pressing (ECAP) has been used to refine the grain size of Mg-12Gd-3Y-0.5Zr billet at about 400°C because it lacks sufficient ductility at low temperatures. However, <0001> peak intensity is oriented about 50° from the extrusion direction, which facilitates the basal slip, and decreases the yield strength. We have employed conventional extrusion at 300°C following ECAP to modify the texture in hard orientation. This two-step process makes use of two strengthening mechanisms a) grain boundary strengthening due to small grain size, and (b) texture strengthening due to grains in hard orientation. The samples processed by the two-step show the yield and ultimate strength to 283 and 308 MPa, respectively. Moreover, the activation of slip and fine grains resulted from the ECAP helped to maintain a good ductility even after significant straining from conventional extrusion.