Tsuru Tomohito, Han Shu, Matsuura Shutaro, Chen Zhenghao, Kishida Kyosuke, Iobzenko Ivan, Rao Satish I, Woodward Christopher, George Easo P, Inui Haruyuki
Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki, 319-1195, Japan.
Center for Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan.
Nat Commun. 2024 Feb 24;15(1):1706. doi: 10.1038/s41467-024-45639-8.
Refractory high-entropy alloys (RHEAs) are of interest for ultrahigh-temperature applications. To overcome their drawbacks - low-temperature brittleness and poor creep strength at high temperatures - improved fundamental understanding is needed. Using experiments, theory, and modeling, we investigated prototypical body-centered cubic (BCC) RHEAs, TiZrHfNbTa and VNbMoTaW. The former is compressible to 77 K, whereas the latter is not below 298 K. Hexagonal close-packed (HCP) elements in TiZrHfNbTa lower its dislocation core energy, increase lattice distortion, and lower its shear modulus relative to VNbMoTaW whose elements are all BCC. Screw dislocations dominate TiZrHfNbTa plasticity, but equal numbers of edges and screws exist in VNbTaMoW. Dislocation cores are compact in VNbTaMoW and extended in TiZrHfNbTa, and different macroscopic slip planes are activated in the two RHEAs, which we attribute to the concentration of HCP elements. Our findings demonstrate how ductility and strength can be controlled through the ratio of HCP to BCC elements in RHEAs.
难熔高熵合金（RHEAs）在超高温应用中具有吸引力。为了克服它们的缺点——低温脆性和高温下较差的蠕变强度——需要更好地从根本上理解它们。通过实验、理论和建模，我们研究了典型的体心立方（BCC）RHEAs，TiZrHfNbTa和VNbMoTaW。前者在77 K时可压缩，而后者在298 K以下不可压缩。相对于元素均为BCC的VNbMoTaW，TiZrHfNbTa中的六方密排（HCP）元素降低了其位错核心能量，增加了晶格畸变，并降低了其剪切模量。螺型位错主导TiZrHfNbTa的塑性，但在VNbTaMoW中刃型位错和螺型位错数量相等。VNbTaMoW中的位错核心紧凑，而TiZrHfNbTa中的位错核心扩展，并且在这两种RHEAs中激活了不同的宏观滑移面，我们将其归因于HCP元素的浓度。我们的研究结果表明了如何通过RHEAs中HCP与BCC元素的比例来控制延展性和强度。
