Effects of Al addition on the microstructure and mechanical property of Al_xCoCrFeNi high-entropy alloys

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• 作者：Woei-Ren Wang^a ; ^b ; Wei-Lin Wang^b ; Shang-Chih Wang^b ; Yi-Chia Tsai^b ; Chun-Hui Lai^b ; Jien-Wei Yeh^a ; ^{jwyeh@mx.nthu.edu.tw}
• 关键词：B. Alloy design ; B. Mechanical properties at ambient temperature ; C. Casting ; D. Microstructure
• 刊名：Intermetallics
• 出版年：2012
• 期刊代码：36_09669795
• 类别：ms
• 出版时间：July, 2012
• 卷：26
• 期：Complete
• 页码：44-51
• 文件大小：1932 K

摘要

A five-component Al_xCoCrFeNi high-entropy alloy (HEA) system with finely-divided Al contents (x in molar ratio, x聽=聽0-2.0) was prepared by vacuum arc melting and casting method. The effects of Al addition on the crystal structure, microstructure and mechanical property were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers hardness tester. The as-cast Al_xCoCrFeNi alloys can possess face-centered cubic (FCC), body-centered cubic (BCC) or mixed crystal structure, depending on the aluminum content. The increase of aluminum content results in the formation of BCC structure which is a dominant factor of hardening. All the BCC phases in the as-cast alloys have a nano-scale two-phase structure formed by spinodal decomposition mechanism. The Al_0.9CoCrFeNi alloy exhibits a finest spinodal structure consisting of alternating interconnected two-phase microstructure which explains its maximum hardness of Hv 527 among the alloys. The chemical composition analysis of FCC and BCC crystal structures, their lattice constants, overall hardness demonstrate that the formation of a single FCC solid solution should have Al addition <11聽at.%and the formation of a single BCC solid solution requires Al addition at least 18.4聽at.%in the Al_xCoCrFeNi system.