Guidelines in predicting phase formation of high-entropy alloys
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Guidelines in predicting phase formation of high-entropy alloys Y. Zhang and Z.P. Lu, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China S.G. Ma, Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024, China P.K. Liaw and Z. Tang, Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996 Y.Q. Cheng, Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 M.C. Gao, National Energy Technology Laboratory, Albany, Oregon 97321; URS Corporation, P.O. Box 1959, Albany, Oregon 97321 Address all correspondence to Y. Zhang at [email protected] (Received 9 October 2013; accepted 4 April 2014)
Abstract With multiple elements mixed at equal or near-equal molar ratios, the emerging, high-entropy alloys (HEAs), also named multi-principal elements alloys (MEAs), have posed tremendous challenges to materials scientists and physicists, e.g., how to predict high-entropy phase formation and design alloys. In this paper, we propose some guidelines in predicting phase formation, using thermodynamic and topological parameters of the constituent elements. This guideline together with the existing ones will pave the way toward the composition design of MEAs and HEAs, as well as property optimization based on the composition–structure–property relationship.
The emerging high-entropy alloys (HEAs) have received increasing attention in recent years. Unlike the traditional alloys, which are typically based on one or two principal elements, HEAs contain multiple elements at equal or nearequal molar ratios.[1–8] The unusual composition can lead to the formation of an extensive solid solution in a face-centered-cubic (FCC) or a body-centered-cubic (BCC) structure as the only or matrix phase and accordingly unique properties.[9,10] For example, Senkov et al.[11] found that the heat-softening resistance of the VNbMoTaW HEA with a BCC structure can remain significant up to 1500 K, whereas for Inconel 718, a superalloy, it starts to diminish at about 873 K and plummets with further heating. Kuznetsov et al.[12] reported that the AlCoCrFeNiCu HEA after forging showed a tensile elongation as high as 864% at 1273 K. Chuang et al.[13] demonstrated that the wear resistance of Co1.5CrFeNi1.5Ti and Al0.2Co1.5CrFeNi1.5Ti HEAs (in molar fraction) is at least twice that of commercial wear-resistant steels with similar hardness. The enhancement is believed to stem from the HEAs’ excellent anti-oxidation ability and resistance to thermal softening. Zhang et al.[14] reported HEAs with high saturation magnetization, electrical resistivity, and malleability. Hemphill et al.[15] found great fatigue resistance of HEAs. The fatigue-endurance limit can compare favorably with conventional materials, such as steels, and nickel, aluminum, titanium alloys, and advanced bulk metallic glasses (BMGs). These interesting properties of HEAs se
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