Phase transition in medium entropy alloy CoCrNi under quasi-isentropic compression. (October 2022)

• Record Type: Journal Article
• Authors: Xie, Zhuocheng; Jian, Wu-Rong; Xu, Shuozhi; Beyerlein, Irene J.; Zhang, Xiaoqing; Yao, Xiaohu; Zhang, Run
• Is Part Of: International journal of plasticity. Volume 157(2022)
• Publication Date: 2022-10
• Subjects: Plastic deformation -- Phase transition -- Chemical short-range order -- Quasi-isentropic compression -- Medium entropy alloy; Plasticity -- Periodicals; Plasticité -- Périodiques; Plasticity; Periodicals; 620.11233
• DOI: 10.1016/j.ijplas.2022.103389
• Languages: English
• ISSNs: 0749-6419

Abstract

Abstract: Under high strain-rate loading, prominent increases in pressure usually triggers phase transition (PT), but the concomitant temperature rise may also cause melting. Quasi-isentropic (QI) compression provides a strategy to explore solid-state phase transition by reducing the temperature rise while retaining high pressure. Using large-scale molecular dynamics simulations, we investigate PTs in single crystal CoCrNi medium entropy alloys (MEAs) under QI compression. With the applied strain rates ranging from 1 0 8 s −1 to 1 0 11 s −1, the strain-rate dependence and anisotropy of yield stress and solid-state PT path are revealed by comparing the mechanical responses along three compressed crystallographic orientations ([100], [1 1 ¯ 0], and [111]). Positive strain-rate sensitiveness is found in the yield stress along the [1 1 ¯ 0] and [111] directions, while insensitiveness along the [100] direction. Various PTs occur alongside massive plastic deformation in the post-yield regime. As the strain rate rises, face-centered-cubic (FCC) to body-centered-cubic (BCC) PT overrides the stacking fault-induced hexagonal-close-packed (HCP) phase formation and dominates the plasticity for the [100] loading. By contrast, crystalline PTs give way to amorphization for [1 1 ¯ 0] and [111] loading at high strain rates. Chemical short-range order hinders dislocation slip and promotes dislocation interactions, which further facilitate early formation of the BCC phase, suggesting a potential strategy to tailor polymorphism in MEAs. Highlights: Phase transition (PT) in CoCrNi medium entropy alloy is studied by MD simulations. medium entropy alloy under quasi-isentropic compression. The effects of loading orientation and strain rate on PT path are investigated. The role of CSRO in incipient plasticity and BCC phase expansion is revealed. The competition between crystalline PTs and amorphization is discussed.