Critical stress for twinning nucleation in CrCoNi-based medium and high entropy alloys

• Published in: Acta materialia Vol. 149; pp. 388 - 396
• Main Authors: Huang, He, Li, Xiaoqing, Dong, Zhihua, Li, Wei, Huang, Shuo, Meng, Daqiao, Lai, Xinchun, Liu, Tianwei, Zhu, Shengfa, Vitos, Levente
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2018
• Subjects: Critical resolved shear stress (CRSS); Density functional theory; Medium and high entropy alloys (MHEAs); Twinning nucleation; Critical resolved shear stress (CRSS); Medium and high entropy alloys (MHEAs); Density functional theory; Twinning nucleation
• ISSN: 1359-6454; 1873-2453; 1873-2453
• DOI: 10.1016/j.actamat.2018.02.037

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. [Display omitted]