Abstract
In this work, we have developed a methodology to obtain an ab initio cluster expansion of a system containing a dislocation and studied the effect of configurational disorder on the 1/2〈111〉 screw dislocation core structure in disordered Mo1−xWx alloys. Dislocation cores control the selection of glide planes, cross slip, and dislocation nucleation. Configurational disorders in alloys can impact the dislocation core structure and affect dislocation mobility. For our calculations, we have used a quadrupolar periodic array of screw dislocation dipoles and obtained the relaxed structures and energies using density functional theory. We have obtained the dislocation core structure as a function of composition and the interaction energies of solutes with the dislocation as a function of position with respect to the core. With these energies, we performed mean-field calculations to assess segregation toward the core. Finally, with the calculated energies of 1848 alloy configurations with different compositions, we performed a first principle cluster expansion of the configurational energetics of Mo1−xWx solid solutions containing dislocations.
Highlights
Alloying has played a key role in producing useful materials from pure metals, enabling the tuning of their strength by the introduction of solutes
The first case, the symmetric or non-degenerate core, the spreading is evenly distributed, whereas in the asymmetric or degenerate core, the spread is not centered on the dislocation core, and it exists in two energetically equivalent symmetric variants
The dislocation core structure can be visualized with the differential displacement maps
Summary
Alloying has played a key role in producing useful materials from pure metals, enabling the tuning of their strength by the introduction of solutes. One of such cases is refractory materials, which are of technological interest due to their high melting point, but they exhibit room temperature brittleness, limiting their resistance to mechanical load. In other materials systems, alloying is a typical method to achieve hardening. This underlines the importance of developing simulation tools to treat dislocations with the accuracy needed for alloy problems
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