Achieving strength–ductility synergy in a non-equiatomic Cr₁₀Co₃₀Fe₃₀Ni₃₀ high-entropy alloy with heterogeneous grain structures

Abstract

Cold rolling and post-deformation annealing (PDA) heat treatments were used to produce heterogeneous grain structures (HGS) in a single-phase face-centered cubic (fcc) Cr₁₀Co₃₀Fe₃₀Ni₃₀ high-entropy alloy (HEA). The microstructural evolution and microstructure–property relationship of the HEA were systematically studied under different states. HGS could be achieved in PDA-treated samples at 875 °C for 20 s and at 900 °C for 20 s (PDA-900-20 s). PDA-900-20 s sample exhibits the most excellent combination of strength and ductility, showing a tensile yield strength of ~ 590 MPa, an ultimate strength of ~ 706 MPa and a total elongation of ~ 23.9%. Additionally, compared with the homogenized counterpart exhibiting homogenous grains, PDA-900-20 s sample displays a notable increment of ~ 413% in yield strength and simultaneously maintains a good ductility. The dominated strengthening mechanisms in PDA-900-20 s sample are grain-boundary strengthening and heterogeneous deformation-induced (HDI) strengthening, whereas the good ductility is mainly resulted from the HDI ductility. Accordingly, the present study provides an effective and simple pathway to overcome the strength–ductility trade-off of typical fcc HEAs through heterogeneous microstructure.

Graphical abstract

摘要

本文采用冷轧和变形后退火热处理(PDA)在单相面心立方(fcc) Cr₁₀Co₃₀Fe₃₀Ni₃₀高熵合金(HEA)中成功获得了异质晶粒结构(HGS)。系统研究了该HEA在不同状态下的组织演化和性能关系。该合金在875 °C, 20 s和900 °C,20 s (PDA-900-20 s) PDA处理后均获得了异质晶粒组织。PDA-900-20 s样品的强度和塑性匹配最佳, 其屈服强度约为590 MPa, 抗拉强度约为706 MPa, 伸长率约为23.9%。与均匀晶粒结构的均质态样品相比, PDA-900-20 s样品的屈服强度显著提高了约413%, 同时保持了良好的塑性。PDA-900-20 s的强化机制主要为晶界强化和非均匀变形诱导(HDI)强化, 良好的塑性主要来源于HDI诱导塑性。本文通过引入异质晶粒组织, 为fcc高熵合金克服强度-塑性倒置提供了一种有效且简单的方法。