Microstructure and Mechanical Properties of Mg-Zn-Gd Alloys After Rolling or Extrusion Processes

摘要

A series of Mg-Zn-Gd alloys were developed for large strain hot rolling, cold rolling and high-speed extrusion. The hot rolled Mg-2.0Zn-0.3Gd (wt%) alloys can be successfully rolled at 300°C for a single pass reduction of 80% without any edge cracks, and the rolled sheet exhibited high yield strength of ～210 MPa and moderate elongation of ～22% due to fine grains and weak basal texture with broad angle distribution. The hot rolled Mg-2.0Zn-0.8Gd sheet showed excellent cold rollability due to the activation of {1012} extension twins and dislocation slips. Cold rolling could further modify the texture and enhance the strength. Besides, Mg-1.58Zn-0.52Gd alloy can be successfully extruded at high die-exit speed of 60 m/min without any surface defects in a wide temperature range due to the absence of thermally unstable eutectic phase and high solidus temperature. The high-speed extruded alloy showed high ductility of ～30%, which was twice than AZ31 alloy, because of the formation of rare earth texture.