Amorphous shear bands that can form in crystalline materials during high-strain-rate deformation are typically precursors to fracture. Since shear bands in crystalline material typically do not persist over a wide range of strain rates, the effect of strain rate on solid-solid phase transformation within shear bands has rarely been discussed. Recent findings reveal that in some materials, shear bands can instead enable plasticity at low strain rates. However, it remains unknown how the mechanics of such shear bands and the resulting mechanical properties depend on the strain rate. Here, the strain-rate dependence of shear bands is investigated in two different compositions of Al-Sm system, where shear bands lead to fracture in one of the compositions and plasticity in the other. We discovered that strain rate directly affects the shear-band density and shear-band behavior, which in turn alters the mechanical properties. In contrast to low strain rates, high strain rates lead to the formation of immature partially amorphous shear bands which then transition into fully amorphous shear bands. The underlying reasons and the mechanisms underlying shear-band formation have been elucidated using a combination of experiments and molecular dynamics simulations across a large range of strain rates.

中文翻译：

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应变速率对 Al-Sm 系统中剪切带行为的影响


在高应变率变形过程中，晶体材料中可能形成的无定形剪切带通常是断裂的前兆。由于晶体材料中的剪切带通常不会在很宽的应变速率范围内持续存在，因此很少讨论应变速率对剪切带内固-固相转变的影响。最近的研究结果表明，在某些材料中，剪切带可以在低应变率下实现塑性。然而，这种剪切带的力学原理和由此产生的机械性能如何取决于应变率仍然未知。在这里，研究了剪切带的应变速率依赖性在 Al-Sm 系统的两种不同组成中，其中剪切带导致其中一种成分的断裂和另一种成分的塑性。我们发现应变率直接影响剪切带密度和剪切带行为，进而改变机械性能。与低应变速率相反，高应变速率导致形成未成熟的部分非晶剪切带，然后转变为完全非晶剪切带。通过在大应变速率范围内结合实验和分子动力学模拟，阐明了剪切带形成的根本原因和机制。