Stabilization of the metastable βʹ phase by forming Cu4(Ti,Sc) crystal structure in Cu–Ti alloys

The βʹ-Cu4Ti phase is the major strengthening precipitate in Cu–Ti alloys. Previous research indicates that destabilization of the βʹ-Cu4Ti phase leads to dissolution of Ti atom from precipitates into the Cu matrix. In the present work, Sc was chosen to be alloying elements in Cu–Ti alloys, since stabilization of the βʹ-Cu4Ti phase could be enhanced by formation of βʹ-Cu4(Ti,Sc) phase. Experimental characterization combined with first-principles calculations were used to evaluate the effect of Sc addition. It was found that the bonding between Ti and Sc atoms in the same sublattice of βʹ-Cu4Ti phase increases the diffusion barrier of Ti atoms, and thus dissolution of the βʹ-Cu4Ti phase and further nucleation of the β-Cu4Ti phase were hindered.