The effects of solute and deformation on the mobility of screw dislocation cores in bcc molybdenum

In body-centered cubic metals such as molybdenum, screw dislocations critically govern the plastic deformation behavior of alloys. The presence of solute atoms in alloys can effectively alter the formation and movement of screw dislocations. In this study, we employed first-principles calculations to delve into the electronic origins of these influences. Initially, we constructed single atomic column and triple atomic column models to simulate the formation of screw dislocations with solute atoms. Our investigation revealed that tantalum (Ta) and tungsten (W) increase the formation energy of solute-dislocation interactions, while osmium (Os), iridium (Ir), and platinum (Pt) have the opposite effect. Subsequently, utilizing a screw dislocation dipole model under shear deformation, we explored the combined effects of solute atoms and deformation on dislocation core movement. We found that Os, Ir, and Pt, located as the first nearest neighbors of the dislocation core, exhibit an attractive effect on the dislocation core. Solute atoms at specific positions can alter the direction of dislocation slip, inducing cross-slip and enhancing material ductility. In contrast, under the same stress, Ta and W exhibit repulsion towards the dislocation core and cannot change the direction of dislocation slip, only altering the energy barrier for dislocation core movement. This work provides atomic-scale insights into solute-induced dislocation dynamics, offering guidelines for advanced Mo alloy design.