Abstract The CrCoNi-based medium and high entropy alloys (MHEAs) have drawn much attention due to their exceptional mechanical properties at cryogenic temperatures. The twinning critical resolved shear stress (CRSS) is a fundamental parameter for evaluating the strength-ductility properties of MHEAs. Here we construct and apply an extended twinning nucleation Peierls-Nabarro (P-N) model to predict the twinning CRSSes of face-centered cubic (FCC) CrCoNi-based MHEAs. The order of the twinning CRSSes of the selected alloys is CrCoNi > CrCoNiMn > CrCoNiFe > CrCoNiFeMn and the values are 291, 277, 274 and 236 MPa, respectively. These theoretical predictions agree very well with the experimental twinning CRSSes of CrCoNi and CrCoNiFeMn accounting for 260 ± 30 and 235 ± 10 MPa, respectively and are perfectly consistent with the strength-ductility properties including yield stress, ultimate tensile stress and uniform elongation for fracture of the FCC CrCoNi-based MHEAs obtained at cryogenic temperatures. The present method offers a first-principle quantum-mechanical tool for optimizing and designing new MHEAs with exceptional mechanical properties.

中文翻译：

---

CrCoNi基中高熵合金孪晶形核的临界应力

摘要 CrCoNi基中高熵合金（MHEAs）因其在低温下的优异机械性能而备受关注。孪生临界分辨剪切应力 (CRSS) 是评估 MHEA 强度-延展性的基本参数。在这里，我们构建并应用扩展孪晶成核 Peierls-Nabarro (PN) 模型来预测面心立方 (FCC) CrCoNi 基 MHEA 的孪晶 CRSSes。所选合金的孪晶 CRSSes 顺序为 CrCoNi > CrCoNiMn > CrCoNiFe > CrCoNiFeMn，其值分别为 291、277、274 和 236 MPa。这些理论预测与 CrCoNi 和 CrCoNiFeMn 的实验孪生 CRSSes 非常吻合，分别为 260 ± 30 和 235 ± 10 MPa，分别与在低温下获得的 FCC CrCoNi 基 MHEA 的强度-延展性特性完全一致，包括屈服应力、极限拉伸应力和均匀断裂伸长率。本方法为优化和设计具有优异机械性能的新型 MHEAs 提供了第一性原理量子力学工具。