Abstract The present study aimed at characterizing the flow characteristics and workability of an as-extruded magnesium alloy ZK61 by isothermal compression tests performed at temperatures of 523–673 K and strain rates of 0.001–1s−1. The flow stress curves were analysed via considering the mechanism of microstructure evolution. Using the obtained flow stress data, both of the conventional and improved Arrhenius constitutive equations were developed to predict the flow characteristics, and the 3D activation energy maps were constructed to propose the optimal deformation conditions and reveal the effects of deformation parameters on microstructure evolution. It can be found that the strain factor plays an important role in determining the shapes of the flow stress curves, which exhibit three types of variation tendencies due to the flow softening and hardening behaviour as the strain increases. The improved constitutive equations resulted in excellent predictability of the peak flow stress within all the deformation conditions. Combining with the activation energy maps, the dominant deformation mechanisms, i.e., dynamic recrystallization and flow localization in different deformation regions were identified, and the optimal processing window of the alloy can be obtained at strain rate and temperature range of 0.001–0.01s−1 and 623 ~ 673 K under a strain of 0.9.

中文翻译：

---

镁合金 ZK61 在热变形过程中的流动表征，使用改进的本构方程和使用活化能图

摘要 本研究旨在通过在 523-673 K 的温度和 0.001-1s-1 的应变速率下进行的等温压缩试验来表征挤压态镁合金 ZK61 的流动特性和可加工性。通过考虑微观结构演化的机制来分析流动应力曲线。使用获得的流动应力数据，开发了传统的和改进的 Arrhenius 本构方程来预测流动特性，并构建 3D 活化能图以提出最佳变形条件并揭示变形参数对微观结构演变的影响。可以发现，应变因子在确定流变应力曲线的形状方面起着重要作用，由于应变增加时的流动软化和硬化行为，它们表现出三种类型的变化趋势。改进的本构方程导致在所有变形条件下峰值流动应力的良好可预测性。结合活化能图，确定了主要变形机制，即不同变形区域的动态再结晶和流动局部化，并在应变速率和温度范围为 0.001–0.01s-1 时获得合金的最佳加工窗口在 0.9 的应变下为 623 ~ 673 K。