Non-Schmid effects in a model refractory multi-principal element alloy: phase-field dislocation dynamics informed by atomistic simulations

Abstract

Non-Schmid effects in a representative refractory multi-principal element alloy (MPEA), MoNbTi, are investigated using molecular statics (MS) and phase field dislocation dynamics (PFDD). In addition to imposing a statistical distribution for the energetic barrier to slip, incorporating properties of the screw dislocation core is critical in capturing the wide range of MS-predicted non-Schmid effects. PFDD energy terms are enhanced to better capture the varying screw dislocation core-widths under loading as informed by MS. These enhancements demonstrate that incorporating the details of screw dislocation cores, in different chemical environments, has the strongest effect on representing the MS-predicted range of non-Schmid effects.Impact StatementVarying degrees of non-Schmid effects, unique to refractory MPEAs, are studied for the first time using atomistic and mesoscale models and are shown to result from environment-dependent properties of screw dislocation cores.

Keywords

• Multi-principal element alloy
• phase field modeling
• non-Schmid effect
• molecular statics
• dislocations