Creep, fatigue, and fracture behavior of high-entropy alloys
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Creep, fatigue, and fracture behavior of high-entropy alloys Weidong Lia) Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA
Gang Wang and Shiwei Wu Laboratory for Microstructures, Institute of Materials, Shanghai University, Shanghai 200444, China
Peter K. Liawb),c) Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA (Received 13 April 2018; accepted 25 May 2018)
As high-entropy alloys (HEAs) are being actively explored for next-generation structural materials, gaining a comprehensive understanding of their creep, fatigue, and fracture behaviors is indispensable. These three aspects of mechanical properties are particularly important because (i) creep resistance dictates an alloy’s high-temperature applications; (ii) fatigue failure is the most frequently encountered failure mode in the service life of a material; (iii) fracture is the very last step that a material loses its load-carrying capability. In consideration of their importance in designing HEAs toward applicable structural materials, this article offers a comprehensive review on what has been accomplished so far in these three topics. The sub-topics covered include a comparison of different creep testing methods, creep-parameter extraction, creep mechanism, high-cycle fatigue S–N relation, fatigue-crack-growth behavior, fracture toughness, fracture under different loading conditions, and fractography. Directions for future efforts are suggested in the end.
I. INTRODUCTION
As materials with superior properties are continuously searched, high-entropy alloys (HEAs), formed by the physical metallurgy of five or more metallic elements with equal or nearly equal quantities, emerge as a class of revolutionary materials.1–5 HEAs break down the traditional wisdom of alloy design in which a primary element serves as the foundation of properties, and small amounts of additional elements are added for fine tuning, therefore, open innumerable possibilities in developing advanced alloys.6 One decade of dedicated research has revealed that many HEAs possess unparalleled properties in comparison with traditional alloys, for instance, great thermal and microstructural stability,7–9 high hardness,10,11 high strength at a wide range of temperatures,12–15 and excellent resistance to wear,16,17 corrosion,18,19 fatigue,20–22 fracture,13,23 and high-temperature softening.5,24,25 Given these merits, applications of HEAs in various fields, particularly in the structural engineering (e.g., used for Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] c) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs. org/editor-manuscripts/. DOI: 10.1557/jmr.2018.191 J. M
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