Rapid solidification and liquid-phase separation of undercooled CoCrCuFexNi high-entropy alloys
Rapid solidification and liquid-phase separation of undercooled CoCrCuFexNi high-entropy alloys
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过冷CoCrCuFexNi高熵合金的快速凝固与液相分离
DOI：
10.1016/j.intermet.2016.01.008
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发表时间：
2016-05-01
期刊：
影响因子：
4.4
通讯作者：
Lu, Y. P.
中科院分区：
文献类型：
--
作者：
Liu, N.;Wu, P. H.;Lu, Y. P.
采用助熔剂循环过热技术研究了CoCrCuFexNi（x = 1.0，1.5，2.0，摩尔浓度）高熵合金的快速凝固行为。研究了CoCrCuFexNi（x = 1.0，1.5，2.0）高熵合金在不同过冷度（Δ T）下的凝固组织。深过冷熔体凝固组织中出现液相分离，形成富铜区和贫铜区。当熔体过冷度超过CoCrCuFeNi合金的160 K、CoCrCuFe 1.5Ni合金的190 K和CoCrCu-Fe 2Ni合金的293 K的临界过冷度（Δ T-crit）时，会发生这种情况。而在过冷度较小（Δ T <Δ T-crit）的快速凝固CoCrCuFexNi合金中观察到典型的枝晶和枝晶间区域。当熔体过冷度Δ T超过临界值Δ T-crit时，合金中出现大量的富Cu球形甚至蛋形组织，基体中出现大量的富Cu纳米相，这可能是富Cu相从凝固过程中形成的过饱和固溶体中析出的结果。多元合金中Cu与其它元素混合的正极性导致在液-固转变开始之前发生液相分离。高熵合金的缓慢扩散效应和快速凝固是铜基合金在固态相变过程中析出纳米相的重要原因。与其他不混溶合金类似，当超过临界过冷度时发生液相分离。在多元CoCrCuFexNi（x = 1.0，1.5，2.0）合金的显微组织中发现了纳米相。(C)2016爱思唯尔有限公司版权所有
Fluxing and cyclic superheating technique was used to investigate the rapid solidification behavior of CoCrCuFexNi (x = 1.0, 1.5, 2.0, molar concentration) high-entropy alloys in this study. The microstructures of CoCrCuFexNi (x = 1.0, 1.5, 2.0) high-entropy alloys solidified at different undercoolings (Delta T) were investigated. Liquid-phase separation leading to Cu-rich and Cu-depleted regions, were obtained in the solidified microstructure from highly undercooled melt. This occurs when the melt undercooling exceeds a critical undercooling (Delta T-crit) of 160 K for CoCrCuFeNi, 190 K for CoCrCuFe1.5Ni and 293 K for CoCrCu-Fe2Ni alloy. However, typical dendrites and interdendritic regions were observed in rapid-solidified CoCrCuFexNi alloys prepared from melts with a small undercooling (Delta T < Delta T-crit). Conversely, a large amount of Cu-rich spheres and even egg-type structures were observed in alloys solidified from melts with large degree of undercooling, Delta T in excess of the critical value, Delta T-crit. A large amount of Cu-rich nano-phases were found in the matrix, possibly, due to the precipitation of Cu-rich phase from the supersaturated solid solution obtained during solidification. The positive enthalpies of mixing between Cu and the other elements in the multi-component alloys resulted in the occurrence of liquid-phase separation prior to the liquid-solid transformation starts. The sluggish diffusion effect of high-entropy alloys and rapid solidification play an important part in the precipitation of nanophase during the solid-state transformation in the Cu-based matrix. Similar to other immiscible alloys, liquid-phase separation occurred when a critical undercooling was exceeded. Differently, nanophases were found in the microstructures of multi-component CoCrCuFexNi (x = 1.0, 1.5, 2.0) alloys. (C) 2016 Elsevier Ltd. All rights reserved.