Abstract The steady state is expected when applying severe plastic deformation (SPD) techniques to process metals. In this study, we propose a method to study the steady state regarding the microstructural features and the mechanical properties, which are verified by the experimental results. More importantly, the initial state of as-prepared metal depending mainly on the processing conditions is critical for the subsequent constitutive relations. Within the framework of dislocation-based crystal plasticity, it is revealed that the dislocation density and flow stress will not change during further deformation when the initial dislocation density is equal to the steady-state value under the loading conditions. In addition, if the initial dislocation density is larger or smaller than the steady-state value, then the dislocation density and flow stress will decrease or increase with increasing strain, and tend to approach the steady-state value. These mechanisms provide not only a physical interpretation for various experimental observations such as near-perfect elastoplasticity, strain hardening and strain softening, but also insightful guidance for investigating the strengthening mechanisms in gradient nano-grained metal produced by SPD.

中文翻译：

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对剧烈塑性变形加工的金属力学性能的新见解

摘要 当应用严重塑性变形 (SPD) 技术来加工金属时，预期会达到稳态。在这项研究中，我们提出了一种研究微观结构特征和机械性能的稳态的方法，并通过实验结果进行了验证。更重要的是，主要取决于加工条件的制备金属的初始状态对于随后的本构关系至关重要。在基于位错的晶体塑性框架内，表明当初始位错密度等于加载条件下的稳态值时，位错密度和流变应力在进一步变形过程中不会发生变化。此外，如果初始位错密度大于或小于稳态值，那么位错密度和流动应力会随着应变的增加而减少或增加，并趋于接近稳态值。这些机制不仅为近乎完美的弹塑性、应变硬化和应变软化等各种实验观察提供了物理解释，而且为研究 SPD 产生的梯度纳米晶粒金属的强化机制提供了深刻的指导。