Deformation temperature impact on microstructure and mechanical properties uniformity of GWZ932K alloy under reciprocating upsetting-extrusion

At present, there are great technical difficulties in achieving microstructure and mechanical properties uniformity in large-size billets prepared by severe plastic deformation technology. How to improve the process route to realize the microstructure and mechanical properties uniformity of the billets has become an urgent problem to be solved at present. In this paper, GWZ932K alloy is used for two reciprocating upsetting-extrusion (RUE) deformation methods with a cumulative strain of 5.38. The influence of isothermal temperature reciprocating upsetting-extrusion (IT-RUE) and decreasing temperature reciprocating upsetting-extrusion (DT-RUE) on the microstructure and mechanical properties uniformity of GWZ932K alloy is discussed in detail. The results show both IT-RUE and DT-RUE deformation methods can effectively refine grains. IT-RUE can prepare Mg alloy billet with uniform microstructure and mechanical properties from center region (CR) to edge region (ER). The microstructure and mechanical properties of the billet prepared by DT-RUE show obvious gradient characteristics from CR to ER. After 4 passes IT-RUE deformation, double-peak textures appear on the (0001) basal texture of the ER, middle region (1/2R) and CR, which is mainly attributed to the occurrence of dynamic recrystallization (DRX) behavior. It should be noted that changes in the deformation temperature will not cause changes in the DRX mechanism. The deformation mechanisms of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) jointly promote grain refinement. (C) 2021 The Author(s). Published by Elsevier B.V.