Phase equilibria, microstructure, and high temperature oxidation resistance of novel refractory high-entropy alloys
Phase equilibria, microstructure, and high temperature oxidation resistance of novel refractory high-entropy alloys
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DOI：
10.1016/j.jallcom.2014.11.012
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发表时间：
2015-03-05
影响因子：
6.2
通讯作者：
Heilmaier, M.
中科院分区：
文献类型：
--
作者：
Gorr, B.;Azim, M.;Heilmaier, M.
提出了一种新的耐火高熵合金系Mo-W-Al-Cr-x作为高温结构应用的候选材料。使用热力学评估将第一合金的化学成分设定为20 Mo-20 W-20 Al-20 Cr-20 Ti（at.%）计算的熔化温度约为1700 ℃。单一无序的BCC相在1077 ℃和1700 ℃之间的高温下应该是稳定的。显微组织检查和XRD结果清楚地表明，在铸态条件下的合金表现出明显的枝晶和枝晶间区域的非均匀的显微组织。然而，热处理工艺揭示了20 Mo-20 W-20 Al-20 Cr-20 Ti合金的强烈的均匀化趋势。虽然具有约800 HV的高硬度，但无裂纹压痕允许假设所研究的合金在室温下可能具有固有的延展性。尽管该合金具有40 at.%高温氧化试验显示出令人惊讶的良好抗氧化性。策略，以提高长期稳定性的无序BCC相，旨在实现所需的机械性能，以及优化合金的化学组成方面的高温抗氧化性进行了讨论。(C)2014爱思唯尔有限公司版权所有。
A new refractory high-entropy alloy system Mo-W-Al-Cr-x is proposed as a family of candidate materials for structural applications at high temperatures. Thermodynamic assessment was used to set the chemical composition of the first alloy as 20Mo-20W-20Al-20Cr-20Ti (at.%) with a calculated melting temperature of about 1700 degrees C. A single disordered BCC phase should be stable at high temperatures between 1077 C and 1700 degrees C. Microstructural examination and XRD results clearly show that the alloy in the as-cast condition exhibits a non-homogeneous microstructure with pronounced dendritic and interdendritic regions. Heat treatment processes, however, reveal a strong tendency of the alloy 20Mo-20W-20Al-20Cr-20Ti to homogenize. While possessing a high hardness of around 800HV, the crack-free indents allow the assumption that the alloy studied may be intrinsically ductile at room temperature. Despite the fact that the alloy possesses 40 at.% of refractory elements, high temperature oxidation tests show a surprisingly good oxidation resistance. Strategies to enhance the long-term stability of the disordered BCC phase aiming at achieving the required mechanical properties as well as optimizing the alloy's chemical composition in terms of high temperature oxidation resistance are discussed. (C) 2014 Elsevier B.V. All rights reserved.