Lattice distortion in a strong and ductile refractory high-entropy alloy
Lattice distortion in a strong and ductile refractory high-entropy alloy
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高强度、延展性难熔高熵合金中的晶格畸变
DOI：
10.1016/j.actamat.2018.08.053
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发表时间：
2018-11-01
期刊：
影响因子：
9.4
通讯作者：
Liaw, Peter K.
中科院分区：
文献类型：
--
作者：
Lee, Chanho;Song, Gian;Liaw, Peter K.
在高熵合金（HEAs）中，具有最佳焓范围的混合熵的最大化可以促进在没有竞争金属间化合物的情况下形成稳定的单一固溶体相。由此产生的效应，如晶格畸变，可以有助于优异的机械性能，这促使人们做出了许多努力来开发和设计单相HEM。然而，挑战仍然存在，特别是在量化晶格畸变并将其与材料性质相关联方面。在这项研究中，我们已经开发了一个NbTaTiV耐火HEA与一个单一的体心立方（BCC）结构，使用综合的实验和理论方法。理论上的努力包括热力学建模，即，相图计算（CALPHAD）。通过系统的热处理工艺研究了组织演变。观察到典型的枝晶组织，这是由于铸态凝固过程中元素偏析造成的。通过在1200 ℃下进行3天的适当均匀化处理，完全消除了结构不均匀性和化学偏析。均匀的元素分布的原子探针层析成像（APT）技术进行了定量验证。重要的是，结果表明，这种HEA在室温和高温（高达900摄氏度）下都表现出高屈服强度和延展性。此外，高混合熵对力学性能的影响进行了讨论和量化的晶格畸变和原子间相互作用的NbTaTiV HEA通过第一性原理计算。研究发现，由于NbTaTiV耐火材料中原子间的相互作用和原子尺寸失配，导致了高能量区的晶格畸变。(C)2018 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The maximization of the mixing entropy with the optimal range of enthalpy in high-entropy alloys (HEAs) can promote the formation of a stable single solid-solution phase with the absence of competing intermetallic compounds. The resultant effects, such as lattice distortion, can contribute to excellent mechanical properties, which has motivated numerous efforts to develop and design single-phase HEM. However, challenges still remain, particularly on quantifying the lattice distortion and relating it to materials properties. In this study, we have developed a NbTaTiV refractory HEA with a single body-pcentered-cubic (BCC) structure using an integrated experimental and theoretical approach. The theoretical efforts include thermodynamic modeling, i.e., CALculation of PHAse Diagram (CALPHAD). The microstructural evolutions have been investigated by systematic heat-treatment processes. The typical dendrite microstructure was observed, which is caused by the elemental segregation during the solidification in the as-cast condition. The structural inhomogeneity and chemical segregation were completely eliminated by the proper homogenization treatment at 1200 degrees C for 3 days. The homogeneous elemental distribution was quantitatively verified by the Atom Probe Tomography (APT) technique. Importantly, results indicate that this HEA exhibits the high yield strength and ductility at both room and high temperatures (up to 900 degrees C). Furthermore, the effects of the high mixing entropy on the mechanical properties are discussed and quantified in terms of lattice distortions and interatomic interactions of the NbTaTiV HEA via first-principles calculations. It is found that the local severe lattice distortions are induced, due to the atomic interactions and atomic-size mismatch in the homogenization-treated NbTaTiV refractory HEA. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.