Stability of α Phase in Ti Alloys Containing Al or Zr from First-Principles Calculations

The energetic and electronic structure of alpha-type Ti1-xXx (X=Al and Zr, x=0.0625, 0.125, 0.185, 0.250, 0.3125and 0.375) binary alloys were calculated by the method of supercell and augmented plane waves plus local orbitals within generalized gradient approximation. The results show that the formation energy decreases with the composition of Al, while increases with composition of Zr, which indicate that alpha phase can be enhanced by increasing the Al contents while weaken by increasing Zr contents. The DOS results shows that the Fermi levels of Ti1-xAlx and Ti1-xZrx fall on a dip of a DOS curve, which means the alpha structure of these alloys is stable. When the Al content is increased, the charge transfer between the Al and its neighbors becomes more evident, and enhance the stability of the alpha phase. With an increase of Zr content, repulsive interaction between two Ti atoms strengthen, which result in the alpha phase stability decrease.