Bain-type distortion and screw-dislocation plasticity in single-crystal MoNbTaTiW refractory high-entropy alloy under orientation- and temperature- controlled tensile loading
International Journal of Refractory Metals and Hard Materials, cilt.141, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 141
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.ijrmhm.2026.107998
- Dergi Adı: International Journal of Refractory Metals and Hard Materials
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Crystallographic anisotropy, Dislocation mechanisms, Molecular dynamics, MoNbTaTiW, Temperature effects
- Karadeniz Teknik Üniversitesi Adresli: Evet
Özet
Understanding the orientation- and temperature-dependent deformation behavior of refractory high-entropy alloys (RHEAs) is essential for designing materials for extreme-service environments. In this study, molecular dynamics simulations were employed to investigate the deformation mechanisms of single-crystal equiatomic MoNbTaTiW RHEA along the ⟨001⟩, ⟨110⟩, ⟨111⟩, and ⟨112⟩ directions over a temperature range of 300–1200 K. The results reveal significant elastic and plastic anisotropy due to the intrinsic characteristics of the BCC lattice. At 300 K, Young's modulus varies from 264 GPa for ⟨001⟩ to 322 GPa for ⟨111⟩. The highest ultimate tensile strength is observed along the ⟨111⟩ direction, measuring 24.59 GPa. In contrast, the ⟨001⟩ orientation demonstrates the greatest ductility and toughness, with a strain to failure of 0.245 and a toughness of 3.98 GJ m−3, nearly double that of ⟨111⟩ under the simulated conditions. As temperature increases, tensile strength and toughness decreases by approximately 16–22%, and 35–41%, respectively. This behavior contrasts with the conventional response of BCC alloys, where elevated temperature typically facilitates screw-dislocation motion and enhances ductility. In MoNbTaTiW, however, temperature-enhanced HCP-like local rearrangements interact with the dominant 1/2⟨111⟩ screw dislocations, hinder uniform plastic flow, and promote damage localization. The deformation mechanism is also orientation dependent: ⟨001⟩ tension promotes Bain-type lattice distortion, whereas the others mainly deform through dislocation glide associated with localized HCP-like configurations. In addition, ⟨100⟩ junction formation contributes to orientation-dependent strain hardening. These findings clarify the coupled effects of crystallographic orientation, temperature, and defect evolution on the deformation response of MoNbTaTiW RHEAs.