Study on the Plasticity Improvement Mechanism of Cryogenic Multi-Directional Forging of Az80 Magnesium Alloy

Abstract

Multi-directional forging (MDF) can effectively improve the mechanical properties of AZ80 magnesium alloy, but it is prone to failure and cracking. Therefore, we try to use cryogenic multi-directional forging to improve the safety limit and mechanical properties. The results showed that compared with the traditional room temperature MDF, the cryogenic MDF increases the deformation tolerance to 1.08. The fine twin effectively divides and refines the grains, obtaining a tensile strength of 512 MPa, a yield strength of 420 MPa and an elongation of 8.2%. With the increase of the number of passes, cryogenic MDF produces rich twin variants and twin interaction structures, which hinder dislocation movement and improve the hardening level of the alloy. On the one hand, abundant twins change the matrix orientation, which is conducive to the activation of basal slip and better coordination of plastic deformation; on the other hand, twin interaction is beneficial to the activation of pyramidal slip and further improves the deformation plasticity.

Keywords: AZ80 Mg Alloy, Multi-directional Forging, Cryogenic, Twin, Plasticity