[SY-C10] Symposium C-10

[SY-C10] First-principles Calculations of Deformation Twins in Hexagonal Titanium Alloys

^○Daisuke Matsunaka, Ryosuke Amano (Dept. of Mechanical Engineering, Shinshu Univ., Japan)

Because of the excellent strength-to-density ratio and the high corrosion resistance, titanium (Ti) and Ti alloys have attracted much attention as aerospace and biomedical materials. One of the methods to improve mechanical properties of Ti is addition of solid solution atoms. For example, the tensile and fatigue strengths of Ti increase with oxygen content, although compromising ductility and toughness. For further development of titanium alloys, detailed understanding of effects of alloying elements on individual deformation modes, various slip and deformation twinning, in hexagonal alpha-titanium alloys is important.
In this study, we investigate twin boundaries and interaction of solute atoms such as Al in alpha-titanium alloys by first-principles calculations. For {11-22} twin, the mirror glide structure is stable, compared with the mirror reflection one and the {10-12} twin boundary. While the {10-12} twin boundary can migrate easily, the energy barrier for migration of the {11-22} twin boundary is relatively high. The interaction of solute atoms with the {10-12} twin boundary depends on the distance and the corresponding boundary sites, i.e., expansion and compression sites. On the other hand, the interaction of solute atoms with the {11-22} twin boundary is complex due to the mirror glide boundary structure.