Effect of backward extrusion on microstructure and mechanical properties of Mg–Gd based alloy

Backward extrusion technology has been performed to improve the mechanical properties of Mg–Gd based alloy. Microstructure, mechanical properties and strengthening mechanism of backward extruded Mg–Gd based alloy were investigated. The average grain size of backward extruded alloy was about 5 μm. The coarse eutectic compounds formed during the solidification were dispersed into polygon-shaped precipitates and were distributed along the extruded direction. The alloy exhibited obviously age hardening response at 225 °C. Both backward extruded state and aged state samples show high thermal stability in the range from room temperature to 200 °C. The ductility of backward extruded alloy at low temperatures was improved greatly compared with the as-cast state sample. The enhanced mechanical properties and thermal stability were mainly attributed to the grain refinement, the dispersed precipitates and fine meta-stable precipitates. It was established that backward extrusion technology was an effective method to manufacture high performance Mg–RE based alloys containing high RE content.