Plastic flow localization is a fundamental and ubiquitous non-equilibrium phenomenon in metallic materials. Despite decades of extensive study, what derives its emergence remains elusive. Here, we tackle this problem in face-centered cubic (fcc) Cantor alloy by the newly developed ramp wave compression technique, which provides a unique quasi-isentropic loading path. By detailed microstructure characterizations, analytical estimation of temperature increment and large-scale atomistic simulations, we conclude that thermal softening is not a dominant driving force for shear band nucleation. Instead, nanotwinning triggers the initial transformation softening which is then accompanied with severe chemical fluctuations and the creation of low-angle dislocation boundaries (LADBs) associated with enhanced local dislocation slips in the adjacent regions. Such LADBs in turn lead to directional softening, acting as the catalytic mediating distortion between neighboring nanotwins. The interconnection between nanotwins and LADBs is thus regarded as structural origin of shear bands, whereas dynamic recrystallization only occurs later during shear band evolution, accelerating strain localization and thickening shear band. These findings shed new lights into fundamental understanding of shear banding and dynamic failure mechanisms in metallic materials.

中文翻译：

---

结构软化介导的高熵合金中的剪切带


塑性流动局域化是金属材料中一种基本且普遍存在的非平衡现象。尽管进行了数十年的广泛研究，但它的出现仍然难以捉摸。在这里，我们通过新开发的斜坡波压缩技术解决了面心立方 （fcc） 康托合金中的这个问题，该技术提供了独特的准等熵加载路径。通过详细的微观结构表征、温度增量的分析估计和大规模原子模拟，我们得出结论，热软化不是剪切带成核的主要驱动力。相反，nanotwinning 触发了初始转化软化，然后伴随着严重的化学波动和低角度位错边界 （LADB） 的产生，这与相邻区域中增强的局部位错滑移相关。这种 LADB 反过来又导致定向软化，充当相邻纳米孪生之间的催化介导失真。因此，纳米孪生和 LADB 之间的互连被认为是剪切带的结构起源，而动态再结晶仅在剪切带演变过程中发生，加速应变局部化和加厚剪切带。这些发现为对金属材料剪切带和动态失效机制的基本理解提供了新的思路。