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How useful is entropy maximization in structural materials design?

Date: 02.05.2016
Time: 1:00 p.m.
Place: ICAMS Advanced Discussions 2016, Bochum, Germany

Easo George, Ruhr-Universität Bochum, Bochum, Germany

High-entropy alloys comprise a novel class of materials that contain multiple principal elements in near-equiatomic concentrations. This is currently a hot topic in materials science, both because of the fundamental issues raised by the chemical complexity of these alloys and because of their potential to be developed as new structural metals. Here, I will evaluate two principal tenets that are frequently invoked in relationship to phase stability and mechanical properties: (1) high configurational entropy favors the formation of solid solutions by suppressing the formation of intermetallic phases, and (2) the higher the configurational entropy the higher the solid solution strengthening. Our results show that both these beliefs are unfounded. Specific counter examples related to the phase stability and mechanical properties of high- and medium-entropy alloys will be presented. In short, it is the nature of the alloying elements, rather than their sheer number, that is important. Even though it has become clear that entropy maximization is not a useful design principle, high-entropy alloys are nevertheless valuable from a basic scientific standpoint to improve understanding of how compositional complexity affects materials properties and phenomena.

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