Compressive deformation of as-extruded LPSO-containing Mg alloys at different temperatures

Abstract

This work investigates the compressive deformation behavior of as-extruded Mg-6Gd-1.6Y–1Zn-0.4Zr (VZ61) and Mg-6Gd-4.8Y–3Zn-0.4Zr (VZ63) alloys via uniaxial compressive tests at various deformation temperatures. At room temperature, compared with the VZ61 alloy, the compressive yield strength of the VZ63 alloy were obviously enhanced due to its increased amount of LPSO phase. Both alloys exhibited a three-stage strain hardening feature. The strain hardening rate first sharply decreases (stage I), then continues to increase at a slower rate (stage II) and finally decreases (stage III). At stage III, a larger number of dislocation accumulation around the kinked LPSO phase resulted in a higher strain hardening rate for VZ63 alloy than that for VZ61 alloy. During high temperature compression, the true stress–strain curves showed that the flow stress gradually reduced with increasing temperature and also the reducing of strain rate, and the VZ63 alloy displayed a higher peak stress than VZ61 alloy. Constitutive equations were constructed based on the true stress–strain to better understand the relation among flow tress (σ), strain rate (ε⋅) and deformation temperature (T) in VZ alloys during hot deformation. The results showed that the VZ63 alloy had a lower deformation activation energy (Q = 255.6 kJ/mol) than VZ61 alloy (Q = 395.5 kJ/mol). The DRX kinetic models of the VZ61 and VZ63 alloys were also established, indicating that the VZ63 alloy was more prone to DRX with a higher volume fraction of dynamically recrystallized grains (XDRX) at the same deformation conditions.

Keywords

• LPSO phase
• Strain hardening
• Dynamic recrystallization
• Hot deformation
• Constitutive equation
• DRX Kinetic model