Microstructure, Crystallographic Orientation and Mechanical Property in AlCoCrFeNi 2.1 Eutectic High-Entropy Alloy Under
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-ENTROPY alloys (HEAs), consisting of five or more elements in equiatomic or near-equiatomic proportion in the range 5 to 35 at. pct as a new alloy development strategy, have generated significant research interest due to their extraordinary and intriguing characteristics, such as high entropy, severe lattice distortion, sluggish diffusion, as well as cocktail effects.[1–4] This novel alloying concept represents a radical departure from the traditional metallurgical design philosophy based on one or two principal elements to satisfy a specific property requirement with various alloying elements added to further optimize properties and performance.[5–7] In HEAs, high configurational entropy leads to lower Gibbs-free energy
JIANTAO WANG, ZHIPENG LONG, and PINFANG JIANG, are with the State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200444, P. R. China. YVES FAUTRELLE is with the SIMAP-EPM-Madylam/G-INP/CNRS, PHELMA, BP 75, 38402 St Martin d’ Heres Cedex, France. XI LI is with the State Key Laboratory of Advanced Special Steels, Shanghai University, and also with the SIMAP-EPM-Madylam/G-INP/CNRS, PHELMA. Contact e-mail: [email protected] Manuscript submitted Jun 01, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
presumed to facilitate the fabrication of simple structured solid solution phases, such as FCC,[8–12] BCC,[13,14] HCP[15,16] and FCC + HCP,[17,18] relative to the precipitation of intermetallic phases. This can confer several valuable characteristics, such as high strength,[13] excellent ductility,[19,20] outstanding wear resistance[21] and thermal stability.[22,23] Nevertheless, it is relatively difficult to achieve an enhanced strength-ductility combination in single-phase HEAs. Commonly, FCC-structure phases exhibit superior ductility but depleted strength,[8–12] while BCC-structure phases can possess enhanced strength but at the expense of ductility.[13,14] In order to realize an enhanced strength-ductility combination for structural application, AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was first proposed by Lu[24] on the basis of the conventional eutectic alloy concept, which combines the characteristics of HEAs and eutectic alloys and consists of a fine lamellar FCC and BCC composite microstructure without visible cast defects. Moreover, the directcast AlCoCrFeNi2.1 EHEA exhibit an attractive strength-ductility combination in a wide temperature range from room temperature down to 196 C and are superior to the HEAs previously reported.[25] To further optimize the properties of AlCoCrFeNi2.1 EHEA, Wani et al.[26,27] and Bhattacharjee et al.[28] performed thermo-mechanical processing consisting of
heavy cold/cryo-rolling and annealing at 800 C for 1 hours, which significantly modified the microstructural morphology and showed an improved strength-ductility combination. Subsequently, Shi et al.[29] developed AlCoCrFeNi2.1 EHEAs with a dual-phase heterogeneous lamellae structure by severe cold-rolling, followed by intermediate temperature non-isothermal annealing in which lamel
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