Preparation of Ultrafine-Grained Mg-Mn-Ce Alloy with High Ductility and Energy Absorption by Coupling Extrusion and Forging

An ultrafine-grained (UFGed) Mg–0.9Mn–0.5Ce (wt.%) alloy with high compressive ductility and energy absorption was developed using a low-temperature deformation method of coupling extrusion and forging. Specifically, the alloy was extruded at 150 °C with an extrusion ratio of 12:1, followed by forging at 200 °C to a true strain of 1.2 along the extrusion direction. The microstructure and plastic mechanism were uncovered using optical microscopy, scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. The microstructure was found to consist of ultrafine dynamically recrystallized (DRXed) grains and fragmented unDRXed grains, exhibiting an average grain size of 1.9 μm after low-temperature extrusion. After forging, new UFGs were gradually generated, a uniform UFGed microstructure with an average grain size of 2.7 μm was obtained, and the texture intensity was decreased as well. The homogenous UFGs and basal slip collaboratively contributed to better comprehensive performance of the UFGed alloy, such as a high compressive ductility of 45.0% and a high energy absorption of 122.72 MJ/m3.