Deformation behavior and dynamic recrystallization of Mg-Y-Nd-Gd-Zr alloy

The characteristics of dynamic recrystallization (DRX) in Mg-Y-Nd-Gd-Zr-RE magnesium alloy were investigated by compression tests at temperatures between 523 and 723 K and at strain rates ranging from 0.002 to 1 s−1 with maximum strain of 0.693. The strain- hardening rate can be obtained from true stress-true strain curves, plots of θ-σ, —(∂̸θ/∂̸σ)-σ and lnθ-σ in different compression conditions were obtained by further study. The critical condition of the onset of DRX process was determined as ((∂̸/∂̸σ)(-∂̸θ/∂̸σ))=0. In the range of the above deformation temperature and strain rate, the ratio of critical stress (σc) to peak stress (σm) and critical strain (ɛc) to the peak strain (ɛm) stood at σc/σm=0.62–0.89 and ɛc/ɛm=0.11–0.37, respectively. DRX could be observed during hot deformation process, microstructure evolution of the magnesium alloy at different temperatures and strain rates were studied with the aid of optical microscope(OM), and the average recrystallized grain size was measured by means of intercepts on photomicrographs. It was shown that the average dynamically recrystallized grain size (drec) changed with different deformation parameters, the natural logarithm of the average recrystallized grain size varied linearly with the natural logarithm of Zener-Hollomon parameter; the peak stress changed with the average recrystallized grain size, and the natural logarithm of the average recrystallized grain size varied linearly with the natural logarithm of the peak stress.