AZ80镁合金热塑性稳定变形工艺参数识别

Identification for the stable hot-working parameters of AZ80magnesium alloy

通过AZ80镁合金多组试样的热物理模拟压缩试验获得在温度523～673K、应变速率0.01～10s-1下的真实应力应变数据,以此作为计算应变速率敏感指数(m值)、能量耗散率(η值)、失稳判据(ξ值)三重指标的底层材料模型。以一组3D曲面形式揭示了应力、温度、应变速率、应变量的共同作用诱导的多种变形机制转化及同时存在所引起的应变速率敏感系数m值的剧烈响应,并通过m值的正负初步识别变形稳定区与失稳区。进一步绘制能量耗散图并识别出η值为负的不稳定变形区,以及η值为正的稳态变形区。在此基础上最后通过失稳判据分布图识别出ξ>0的稳定变形区、ξ≤-1的失稳变形区、-1<ξ≤0的亚稳定变形区。综合识别后,具有较高m值水平、较高η值水平、较高ξ值水平的稳定变形参数区间为优先推荐,具有负m值水平、负η值水平、负ξ值水平的失稳变形参数区间为避免推荐。

Several series of billet samples are compressed on physical simulation machine under deformation temperatures 523～673Kand strain rates 0.01～10s-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 3Dsurfaces 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 mvalue 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.