Eshed Eyal, Larianovsky Natalya, Kovalevsky Alexey, Popov Vladimir, Gorbachev Igor, Popov Vladimir, Katz-Demyanetz Alexander
Israel Institute of Metals, Haifa 3200003, Israel.
Institute of Metals Physics Ural Branch of RAS, 620041 Ekaterinburg, Russia.
Materials (Basel). 2018 Jan 23;11(2):175. doi: 10.3390/ma11020175.
Refractory-based high entropy alloys (HEAs) of the 2nd-generation type are new intensively-studied materials with a high potential for structural high-temperature applications. This paper presents investigation results on microstructural evolution and phase formation in as-cast and subsequently heat-treated HEAs at various temperature-time regimes. Microstructural examination was performed by means of scanning electron microscopy (SEM) combined with the energy dispersive spectroscopy (EDS) mode of electron probe microanalysis (EPMA) and qualitative X-ray diffraction (XRD). The primary evolutionary trend observed was the tendency of Zr to gradually segregate as the temperature rises, while all the other elements eventually dissolve in the BCC solid solution phase once the onset of Laves phase complex decomposition is reached. The performed thermodynamic modelling was based on the Calculation of Phase Diagrams method (CALPHAD). The BCC A2 solid solution phase is predicted by the model to contain increasing amounts of Cr as the temperature rises, which is in perfect agreement with the actual results obtained by SEM. However, the model was not able to predict the existence of the Zr-rich phase or the tendency of Zr to segregate and form its own solid solution-most likely as a result of the Zr segregation trend not being an equilibrium phenomenon.
第二代难熔基高熵合金（HEAs）是新的受到广泛研究的材料，在高温结构应用方面具有很大潜力。本文展示了在不同温度 - 时间条件下，铸态及后续热处理的高熵合金微观结构演变和相形成的研究结果。微观结构检查通过扫描电子显微镜（SEM）结合电子探针微分析（EPMA）的能量色散光谱（EDS）模式和定性X射线衍射（XRD）进行。观察到的主要演变趋势是，随着温度升高，Zr逐渐偏析，而一旦达到Laves相复杂分解的起始点，所有其他元素最终都会溶解在体心立方（BCC）固溶体相中。所进行的热力学建模基于相图计算方法（CALPHAD）。该模型预测，随着温度升高，BCC A2固溶体相中Cr的含量会增加，这与通过SEM获得的实际结果完全一致。然而，该模型无法预测富Zr相的存在或Zr偏析并形成其自身固溶体的趋势，这很可能是由于Zr的偏析趋势不是一种平衡现象。
