Modeling Dislocation Dynamics in Refractory Multi-Principal Element Alloys

Lauren Fey, University of California, Santa Barbara

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Refractory multi-principal element alloys (RMPEAs) are candidate materials for high-temperature structural applications. Composed of several different element types in a random solid solution, the degree of short-range order can be affected by annealing processes. Because mechanical response of RMPEAs can be dependent on short-range order, there is an opportunity to tune the properties of these materials by introducing short-range order. We use a multi-scale simulation model to study and compare the influence of short-range order on the mechanical properties of two RMPEAs, MoNbTi and TaNbTi. An interatomic potential for the Mo-Nb-Ta-Ti system is developed via machine learning and used to calculate the degree of short-range order at two annealing temperatures. These results are then inputted into a mesoscale phase-field dislocation dynamics model to predict the mechanical response of the two alloys. We find the MoNbTi has a higher propensity for short-range order, and this leads to an increase in the stress required to initiate dislocation glide. We also show how the dislocation glide mechanisms and morphologies are affected by short-range order through an increase in the dislocation critical glide stress.

Abstract Author(s): Lauren T. W. Fey, Hui Zheng, Shyue Ping Ong, Irene J. Beyerlein