Solute-induced solid-solution softening and hardening in bcc tungsten

The solute-induced softening and hardening effects in bcc W for twenty-one substitutional alloying elements (Al, Co, Cr, Fe, Hf, Ir, Mn, Mo, Nb, Ni, Os, Pd, Pt, Re, Rh, Ru, Ta, Tc, Ti, V and Zr) are examined to search for a similar softening effect as that observed with Re. The changes in energy barriers of dislocation motion caused by solute-dislocation interactions are directly computed via a first-principles approach with flexible boundary conditions. The effect of solutes on the critical resolved shear stress of the ½ <111> screw dislocation in bcc W at room temperature is quantitatively predicted, as a function of alloy concentration, via a mesoscopic solid-solution model using the first-principles results as input. Al and Mn are proposed to be promising substitutes for Re as these two elements introduce similar softening effects as Re in bcc W. In addition, the trends of the solute-dislocation interactions, and their correlations to the dislocation core structure geometries are discussed.