Hot deformation behavior and microstructure evolutions of as-forged Mg-Gd-Y-Zn-Zr alloy

Abstract

The hot deformation behavior of Mg-9.16Gd-3.03Y-1.44Zn-0.61Zr alloy was examined by hot compression experiments at 623–753 K with strain rates 0.1–20 s−1. Flow stress-strain curves developed an Arrhenius-type equation with adjustment for strain. The influence of strain on microstructure evolution was studied by optical microscope. The results showed that with the increase of deformation, LPSO phase broken and kinked and interacted with dislocations to promote nucleation of dynamic recrystallization (DRX) grains. In addition, the effects of temperature and strain rate on DRX during hot compression were examined using electron back-scatter diffraction. The results demonstrated that the volume fraction of DRX grains improved as temperature and strain rate increased. The alloys could adapt to plastic deformation caused mostly by continuous and discontinuous dynamic recrystallization. Transmission electron microscopy was then utilized to observe the phase structure. The dynamic precipitates occurred after hot compression, and the LPSO phase was broken and kinked, which coordinated the plastic deformation. Using the Avrami equation, the DRX dynamic model of the alloy at 0.1 s−1 was established for the first time.

Keywords

• Mg-Gd-Y-Zn-Zr alloy
• Hot compression
• Constitutive equation
• Microstructure
• Dynamic recrystallization
• Recrystallization kinetics