Corrosion mechanism of an equimolar AlCoCrFeNi high-entropy alloy additively manufactured by electron beam melting
Corrosion mechanism of an equimolar AlCoCrFeNi high-entropy alloy additively manufactured by electron beam melting
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DOI：
10.1038/s41529-020-00127-4
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发表时间：
2020-08-11
影响因子：
5.1
通讯作者：
Chiba, Akihiko
中科院分区：
文献类型：
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作者：
Yamanaka, Kenta;Shiratori, Hiroshi;Chiba, Akihiko
高熵合金（HEAs）已经成为一类具有各种吸引人的特性的结构合金，并且它们在增材制造中的应用使得前所未有的热历史和几何复杂性成为可能，从而有望实现先进材料。本研究调查的腐蚀行为和钝化膜特性的等摩尔AlCoCrFeNi HEA增材制造的电子束熔化（EBM）。动电位极化在3.5重量%的NaCl溶液中显示，底部部分的EBM试样显示出更好的腐蚀性能比常规制备的铸造试样在腐蚀和钝化电流密度方面，而在没有任何明显的钝化电流密度的连续增加，观察到在阳极极化的顶部。电化学阻抗谱研究表明，试样之间的钝化膜特性的显着差异，并揭示了增强的电荷转移电阻和形成的底部部分的一个更具保护性的钝化膜。元素的再分配，特别是，在EBM过程中的合金的熔化后的高温暴露过程中，在B2相的Cr的富集，是负责的钝化膜的稳定性的改善，延缓底部的B2相的选择性溶解。这些研究结果表明，在EBM过程中的“原位退火”所造成的微观结构的演变显着影响的HEA的腐蚀行为。
High-entropy alloys (HEAs) have emerged as a class of structural alloys with various attractive properties, and their application in additive manufacturing, which enables unprecedented thermal history and geometrical complexity, is promising for realising advanced materials. This study investigates the corrosion behaviour and passive film characteristics of an equimolar AlCoCrFeNi HEA additively manufactured by electron beam melting (EBM). Potentiodynamic polarisation in a 3.5 wt% NaCl solution revealed that the bottom part of the EBM specimen shows better corrosion performance than a conventionally prepared cast specimen in terms of both corrosion and passivation current density, while a continuous increase in the current density without any apparent passivity was observed during the anodic polarisation of the top part. The electrochemical impedance spectroscopic study indicated significant differences in the passive film characteristics between the specimens, and revealed an enhanced charge-transfer resistance and the formation of a more protective passive film of the bottom part. The elemental redistribution, in particular, the enrichment of Cr in the B2 phase during the post-melt high-temperature exposure of the alloy during EBM, was responsible for the improved stability of the passive film, retarding the selective dissolution of the B2 phase in the bottom part. These findings indicate that the microstructural evolution caused by 'in situ annealing' during the EBM process significantly influences the corrosion behaviour of the HEA.