Simultaneously improving the deformation tolerance and mechanical properties of AZ80 magnesium alloy through the combination of pre-cryogenic and Multi-directional forging

This study reports an approach to improve the mechanical properties of AZ80 magnesium alloy by combining rapid Multi-directional forging (MDF) and pre-cryogenic process. Compared to the tolerable strain of 0.96 with yield strength of 319 MPa, tensile strength of 469 MPa and elongation of 6.4 % obtained under direct room temperature MDF, the alloy achieved a higher cumulative strain of 1.44 and an increased yield stress of 380 MPa, tensile strength of 502 MPa, with moderate elongation of 6.0 % through the pre-cryogenic step. More interactions among twinning variants and the activation of new {1 0 -1 2}-{1 0 -1 2} or tertiary twinning sequences in cryogenic MDF sufficiently coordinated plastic deformation, thus greatly improving the deformation limit. Furthermore, the pronounced twinning interactions enormously facilitated grain size reduction, texture dispersion, and the accumulation of dense dislocations, all of which served to the superior mechanical properties.