Electronic Origin of Hardening and Softening Via Screw Dislocation Formation in Bcc Tantalum Alloys

Abstract

Improving the high- and low-temperature performance of tantalum (Ta) alloys is challenging. Using first-principles calculations, we studied the interaction between screw dislocations and solute atoms in the BCC structure of Ta, focusing on solid solution softening and hardening. We assessed various solute elements' effects on generalized stacking fault energy (GSFE), energy barriers, and dislocation interactions. Hf and Zr notably soften BCC Ta by reducing GSFE, energy barriers, and interaction energies, while Nb has minimal impact, and Mo, W, and Ir cause hardening. The interaction energy between dislocations and solute atoms predicts these effects. We also extend our findings to ternary alloys, explaining strengthening and softening through the electronic work function.

Keywords: tantalum (Ta) alloys, First-principles calculations, Screw dislocations