Abstract
The generalized stacking fault energy is a key ingredient to mesoscale models of dislocations. Here we develop an approach to quantify the dependence of generalized stacking fault energies on the degree of chemical disorder in multicomponent alloys. We introduce the notion of a “configurationally-resolved planar fault” (CRPF) energy and extend the cluster expansion method from alloy theory to express the CRPF as a function of chemical occupation variables of sites surrounding the fault. We apply the approach to explore the composition and temperature dependence of the unstable stacking fault energy (USF) in binary Mo–Nb alloys. First-principles calculations are used to parameterize a formation energy and CRPF cluster expansion. Monte Carlo simulations show that the distribution of USF energies is significantly affected by chemical composition and temperature. The formalism is broadly applicable to arbitrary crystal structures and alloy chemistries and will enable the development of rigorous models for deformation mechanisms in high-entropy alloys.
Highlights
The effect of compositional fluctuations and configurational ordering on the properties of a dislocation is a long-standing problem in materials science[1,2,3]
We have developed a rigorous approach to describe the dependence of generalized stacking fault energies on the degree of ordering in multicomponent alloys
The approach relies on the decomposition of the bicrystal energy into a long-range configurational contribution and a local planar fault energy, referred to as a configurationally-resolved planar fault” (CRPF)
Summary
The effect of compositional fluctuations and configurational ordering on the properties of a dislocation is a long-standing problem in materials science[1,2,3]. Models that are able to link the properties of a dislocation to the degree of long-range and short-range chemical ordering in multicomponent alloys are necessary to provide fundamental insights about the role of chemistry on mechanical properties. The GSF energy is equal to the work required to displace two halves of a perfect crystal relative to each other along a particular crystallographic plane It is an essential ingredient in Peirls–Nabarro[16,17,18] and phase-field models[19,20,21,22] of dislocations, where it is used to assess the energy penalty due to a disregistry between the adjacent crystallographic planes across the slip plane of a dislocation. The GSF energy can provide qualitative insights about dislocation core structures and preferred partial dislocation structures[23]
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