Fundamental understanding of mechanical behavior of high-entropy alloys at low temperatures: A review
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Fundamental understanding of mechanical behavior of high-entropy alloys at low temperatures: A review Zongyang Lyu, Xuesong Fan, Chanho Lee, Shao-Yu Wang, Rui Feng, and Peter K. Liawa),b) Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA (Received 1 May 2018; accepted 11 July 2018)
The basic principle of high-entropy alloys (HEAs) is that high mixing entropies of solid-solution phases enhance the phase stability, which renders us a new strategy on alloy design. The current research of HEAs mostly emphasizes mechanical behavior at room and higher temperatures. Relatively fewer papers are focused on low-temperature behaviors, below room temperature. However, based on the published papers, we can find that the low-temperature properties of HEAs are generally excellent. The great potential for cryogenic applications could be expected on HEAs. In this article, we summarized and discussed the mechanical behaviors and deformation mechanisms, as well as stacking-fault energies, of HEAs at low temperatures. The comparison of low-temperature properties of HEAs and conventional alloys will be provided. Future research directions will be suggested at the end.
I. INTRODUCTION
Traditional alloys are designed, usually, based on one element as the principal component with several minor elements, e.g., steels are based on iron with C, Ni, Co, Mo, Ti, etc. as the minor elements. Nowadays, there is a new alloying-design strategy called high-entropy alloys (HEAs), which is also known as multiprincipal element alloys, complex concentrated alloys, compositionally complex alloys, baseless alloys, and metal buffets.1–6 As proposed by Yeh,1,7 HEAs could be defined from two different viewpoints. From the perspective of the compositions of alloys, HEAs are stated as the alloys, which have at least five principal elements, and the at.% of each element should be within 5–35%. Minor elements, if the HEAs have, usually possess atomic percentages less than 5%. The other definition, which is based on the configurational entropy, shows that HEAs are alloys whose configurational entropies are larger than 1.5R, where R is the ideal gas constant, in the random condition. In both of the two definitions, HEAs have single or multiple solidsolution structures as major phases, such as face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) phases. Some HEAs possess intermetallics as strengthening phases, such as L128 and B29–11 a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manu
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