Atomistic modeling of nanoscale plasticity in high-entropy alloys
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Atomisticmodelingofnanoscaleplasticityinhigh-entropy alloys Zachary H. Aitken1, Viacheslav Sorkin1, Yong-Wei Zhang1,a) 1
Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore Address all correspondence to this author. e-mail: [email protected]
a)
Received: 23 October 2018; accepted: 28 January 2019
Lattice structures, defect structures, and deformation mechanisms of high-entropy alloys (HEAs) have been studied using atomistic simulations to explain their remarkable mechanical properties. These atomistic simulation techniques, such as first-principles calculations and molecular dynamics allow atomistic-level resolution of structure, defect configuration, and energetics. Following the structure–property paradigm, such understandings can be useful for guiding the design of high-performance HEAs. Although there have been a number of atomistic studies on HEAs, there is no comprehensive review on the state-of-the-art techniques and results of atomistic simulations of HEAs. This article is intended to fill the gap, providing an overview of the state-of-the-art atomistic simulations on HEAs. In particular, we discuss how atomistic simulations can elucidate the nanoscale mechanisms of plasticity underlying the outstanding properties of HEAs, and further present a list of interesting problems for forthcoming atomistic simulations of HEAs.
Introduction Traditional metal alloying involves adding small amounts of secondary elements to a principal parent metal. Understanding of the resulting material properties is based on the obtained solid solution or presence of secondary phases. Inclusion of further elements typically results in brittle intermetallic compounds, but a novel alloying technique allows the introduction of multiple principal elements in equiatomic or nearequiatomic composition to form a solid solution referred to as high-entropy alloy (HEA). This new class of alloys has shown many superior mechanical properties that can outperform traditional binary, ternary, and even superalloys. Since some of the earlier successful reports on fabrication of HEAs [1, 2, 3], several reviews have been written on their microstructure and material properties [4, 5, 6, 7], including focused reviews on mechanical [8] and corrosion properties [9]. The original application of the name “high-entropy alloy” was intended to imply the proposed stabilizing force of the high mixing entropy over the enthalpy in forming a solid solution. Attempts have been made to apply a set of compositional guidelines to define a HEA, although a strict definition remains elusive and the term used in the literature today refers to a broad class of alloys. Originally a HEA was defined as an alloy
ª Materials Research Society 2019
with five or more principal elements, with each element having a concentration between 5 and 35 at.% [4], although it has been shown that some of the alloying effects of HEAs are present in alloys with fewer principal components [10, 11]. It is also important to point out that for a given set of alloying
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