High elongation heterostructure rare earth magnesium alloy based on rotating backward extrusion process

In this paper, Mg-9.5Gd-4Y-2Zn-0.5Zr cylindrical parts were prepared by the conventional backward extrusion ( CBE ) process and rotating backward extrusion ( RBE ) process. The effects of the two processes on the microstructure and mechanical properties of different orientation regions of rare earth magnesium alloy were analyzed and compared. The RBE process introduces a torsional shear quantity based on the CBE process. By changing the direction of plastic flow, has a positive effect on the elongation ( EL ) of the alloy. It was found that dynamic recrystallization ( DRX ) occurred in both CBE and RBE processes. With the transition of deformation, the strain continues to accumulate, and the DRX mechanism changes from discontinuous dynamic recrystallization ( DDRX ) to continuous dynamic recrystallization ( CDRX ). Compared with the CBE process, the grain refinement of the RBE process is more significant. After deformation, a more significant heterostructure is obtained in the RBE-45 ° region, and the average grain size reaches 24.7 μm. The ultimate tensile strength ( UTS ), yield strength ( YS ), and EL of the alloy in this region are 292.5 ± 7.7 MPa, 226.6 ± 7.4 MPa, and 21.5 ± 1.3 %, respectively. Although the strength is slightly lower than that of CBE alloy, better plasticity is obtained. The excellent strength-toughness synergy is attributed to the synergistic effect between heterogeneous regions of non-uniform microstructure. This study provides some theoretical guidance for the industrial production of large-size magnesium alloy cylindrical parts and subsequent applications.