Hierarchical phase evolution in a lamellar Al0.7CoCrFeNi high entropy alloy involving competing metastable and stable phases

SCRIPTA MATERIALIA

卷:204

Article

Srimark, K.¹  Dasari, S.²  Sharma, A.²  Wangyao, P.³  Gwalani, B.⁴  Rojhirunsakool, T.¹  Gorsse, S.⁵  Banerjee, R.² 

[1] King Mongkuts Univ Technol, High Temp Corros Res Ctr, Dept Mat & Prod Technol, Bangkok 10800, Thailand

[2] Univ North Texas, Dept Mat Sci & Engn, Denton, TX 76207 USA

[3] Chulalongkorn Univ, Fac Engn, Dept Met Engn, Bangkok 10330, Thailand

[4] Pacific Northwest Natl Lab, Phys & Computat Sci Directorate, 902 Battelle Blvd, Richland, WA 99352 USA

[5] Univ Bordeaux, CNRS, Bordeaux INP, ICMCB,UMR 5026, F-33600 Pessac, France

关键词: High entropy alloys;    Complex concentrated alloys;    Eutectic microstructure;    Widmanstatten;    Intermetallic precipitates;   

DOI  :  10.1016/j.scriptamat.2021.114137

来源: Elsevier

【 摘 要 】

Guided by solution thermodynamic modeling coupled with detailed experimental characterization, the present study establishes that the alternating FCC and BCC lamellar microstructure in the Al0.7CoCrFeNi high entropy alloy, is a result of non-equilibrium partitionless solidification from the liquid to single B2 phase, followed by solid-state decomposition. Widmanstatten FCC lamellae form from the allotriomorphic FCC precipitates at the B2 grain boundaries, leading to a lamellar microstructure, divided into two distinct sub-systems. Isothermal annealing further drives these individual sub-systems towards equilibrium via precipitation of ordered intermetallic phases. The transformation in FCC lamellae initiates by the formation of metastable L1(2) precipitates at shorter annealing times, which are eventually replaced by the equilibrium BCC and B2 phases, forming composite B2+BCC laths, on long term annealing. These results further exemplify that interesting transformation pathways lead to hierarchical microstructures within HEAs, and the fact that as processed conditions in these alloys are often far-from equilibrium. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

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