Severe plastic deformation can effectively refine alloy microstructure and improve the mechanical properties of alloys surprisingly. In this work, a new approach of severe plastic deformation was proposed based on split Hopkinson pressure bar, i.e., cyclically multi-directional impact. Using this newly developed technique for microstructural refinement at different temperatures (77 K, 293 K, and 1073 K), bulk equiatomic CoCrNi medium entropy alloys with refined microstructures were obtained, and the stress vs. strain relation of the equiatomic CoCrNi medium entropy alloy during the cyclically multi-directional impact can be in situ measured. The strain rate of the cyclically multi-directional impact was controlled at about 1500 /s. The hardnesses of the CoCrNi medium entropy alloy increase dramatically from 216 Hv to 460 Hv after the cyclically multi-directional impact at 77 K, 484 Hv after the cyclically multi-directional impact at 293 K, and 434 Hv after the cyclically multi-directional impact at 1073 K. The microstructural evolutions of the CoCrNi MEA after cyclically multi-directional impact at three temperatures were characterized and analyzed. This study aims to provide a new approach to microstructural refinement for bulk alloys.

中文翻译：

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循环多向冲击温度对等原子CoCrNi中熵合金显微组织细化的影响


剧烈的塑性变形可以有效地细化合金的显微组织，并令人惊讶地提高合金的力学性能。在这项工作中，提出了一种基于分裂霍普金森压力杆的严重塑性变形的新方法，即循环多向冲击。利用这种新开发的技术在不同温度（77K、293K和1073K）下进行微观结构细化，获得了具有细化微观结构的大块等原子CoCrNi中熵合金，并得到了等原子CoCrNi中熵合金在高温过程中的应力应变关系。可以就地测量周期性多向影响。循环多向冲击的应变速率控制在1500/s左右。 CoCrNi中熵合金经77K循环多向冲击后硬度由216 Hv急剧增加至460 Hv，经293K循环多向冲击后硬度为484 Hv，经循环多向冲击后硬度为434 Hv在 1073K 下，对 CoCrNi MEA 在三个温度下循环多向冲击后的微观结构演变进行了表征和分析。本研究旨在提供一种细化大块合金微观结构的新方法。