Identification for the stable hot-working parameters of AZ80 magnesium alloy

Several series of billet samples are compressed on physical simulation machine under deformation temperatures 523～673 K and strain rates 0.01～10 s-1, and the true stress-strain data collected result in the performance of calculations for strain rate sensitivity (m-value), power dissipation efficiency (η-value) and instability parameter (ξ-value). A series of 3D surfaces reveal the severe response of m-value to the evolution and coexisting of several deformation mechanisms induced by the enhanced effect of stress, temperature, strain rate and strain, from which the unstable deformation parameter regions are identified preliminarily. Furthermore, the maps of power dissipation efficiency are plotted, from which the unstable (η≤0) deformation parameter regions are indentified. Finally, based on the map of instability criterion, stable region (ξ＞0), unstable region (ξ≤-1) and metastable region (-1＜ξ≤0) are clarified clearly. According to the comprehensive identification, the stable deformation parameter regions with higher m-value level and higher η-value level and higher ξ-value level are recommended, while the unstable deformation parameter regions with negative m-value level and negative η-value level and negative ξ-value level should be avoided.

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