Huang Shuo, Li Wei, Holmström Erik, Vitos Levente
Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, SE-100 44, Sweden.
Sandvik Coromant R&D, 126 80, Stockholm, Sweden.
Sci Rep. 2018 Aug 22;8(1):12576. doi: 10.1038/s41598-018-30892-x.
Recent developments of high-entropy alloys with high strength and high ductility draw attention to the metastability-engineering strategy. Using first-principle theory, here we demonstrate that reducing the Ta level in the refractory TiZrHfTa system destabilizes the body-centered cubic (bcc) phase and leads to the appearance of the hexagonal close-packed (hcp) phase embedded in the bcc matrix. The alloying-induced features of the elastic parameters for the cubic and hexagonal structures are mapped out in details, and strong sensitivity to the crystal lattice and chemistry is revealed. Results show softening of the bcc matrix with decreasing Ta concentration which ensures ductile behavior. However, the elastically nearly isotropic hcp precipitates possess enhanced resistance against shear which promotes strengthening of the TiZrHfTa dual-phase system. The present atomic-level insight provides strong evidence to the experimental observation, and emphasizes the significance of quantum-design for advanced multi-phase high-entropy alloys with excellent strength-ductility combinations.
具有高强度和高延展性的高熵合金的最新进展引发了对亚稳性工程策略的关注。利用第一性原理理论，我们在此证明，降低难熔TiZrHfTa体系中的Ta含量会使体心立方（bcc）相不稳定，并导致在bcc基体中出现六方密排（hcp）相。详细绘制了立方和六方结构的弹性参数的合金化诱导特征，并揭示了对晶格和化学的强烈敏感性。结果表明，随着Ta浓度的降低，bcc基体软化，这确保了韧性行为。然而，弹性近各向同性的hcp析出相具有增强的抗剪切能力，这促进了TiZrHfTa双相体系的强化。目前的原子水平见解为实验观察提供了有力证据，并强调了量子设计对于具有优异强度-延展性组合的先进多相高熵合金的重要性。
