Dynamic Recrystallization Mechanism of High-Strength Mg-Gd-Y-Zn-Mn Alloy by Hot Compression Deformation

Abstract

The Mg-8Gd-3.5Y-1.5Zn-0.8Mn (wt%) alloy was designed and prepared to. investigate the synergistic dynamic recrystallization (DRX) mechanism at high temperature and low strain rate. We studied DRX process at different strain rates and temperatures, and revealed the corresponding mechanisms. The results show that at a low strain rate of 0.01 s-1 and 723 K, the grain size significantly decreases compared to 623 K, the grain boundaries protrude outward, and new small grains are generated. Quantitative calculations indicate that the thermal deformation mechanism can be reflected by the dissipation efficiency factor η. As the value of η increases, the dynamic softening mechanism shifts from dynamic recovery (DRV) to DRX. When the value of η is greater than 0.36, under these conditions, continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occur. This is because a large number of dislocations accumulate and entangle near the grain boundaries to low angle grain boundaries (LAGBs), which develop into high angle grain boundaries (HAGBs) during deformation. The continuous movement of (HAGBs) leads to the formation of CDRX processes. CDRX provides nucleation sites for DDRX, and the outward protruding grain boundaries promote dynamic recrystallization nucleation. The distortion energy difference between the new grains and the surrounding matrix promotes the continuous movement of LAGBs, ultimately leading to the growth of crystal nuclei and the formation of recrystallized grains. The results indicate that controlling the hot working conditions can improve the microstructure of the alloy through recrystallization, thereby developing high-strength magnesium alloys.

Keywords: Mg alloy, DRX mechanism, hot deformation, Microstructure evolution