Fig 1. Optical microstructure of homogenized Mg alloy GW83.

Fig. 2. Experimental procedure for the double-pass hot compression.

Fig. 3. Stress-strain curve (a) and hardening rate-stress curve (b) under double-pass hot compression at temperature T = 350 °C and strain rate$\dot{\varepsilon}$ = 0.1 s-1.

Fig. 4. Stress-strain curves under double pass hot compression tests at different deformation conditions. (a) ε1 = 0.6, $\dot{\varepsilon}$= 0.1 s-1, (b) ε1 = 0.6, $\dot{\varepsilon}$= 0.01 s-1, (c) ε1 = 0.3, $\dot{\varepsilon}$= 0.1 s-1, (d) ε1 = 0.3, $\dot{\varepsilon}$= 0.01 s-1.

Fig. 5. Stress-strain curves under double-pass hot compression at different holding time. (a) $\dot{\varepsilon}$ = 0.1 s-1, (b) $\dot{\varepsilon}$ = 0.01 s-1.

Fig. 6. Optical microstructure after first pass deformation under different holding time at 350 °C and strain rate of 0.1 s-1. (a)Δt = 0 s, (b)Δt = 60 s, (c) Δt = 120 s, (d)Δt = 180 s. The strain of first pass deformation is set as 0.6.

Fig. 7. Variation of the second pass peak stress under different Z parameter (a) and the linear relationship between ln[sinh(ασp)] and lnZ (b).

Fig. 8. Optical microstructure under different first pass strains and strain rates with temperature T = 350 °C and holding time Δt = 120 s. (a) ε1 = 0.6, $\dot{\varepsilon}$ = 0.1 s-1, (b) ε1 = 0.6, $\dot{\varepsilon}$ = 0.01 s-1, (c) ε1 = 0.3, $\dot{\varepsilon}$ = 0.1 s-1, (d) ε1 = 0.3, $\dot{\varepsilon}$ = 0.01 s-1.

Fig. 9. Hardening fraction (a) and MDRX fraction (b) under different holding time at temperature of 350 °C and strain rate of 0.1 s-1. Strain of first pass deformation is set as 0.6.

Fig. 10. Hardening fraction under different Z parameter (a) and MDRX fraction at 350 °C during non-deformation stage (b).