First‐Principles Study of the Intrinsic Properties of the fcc/hcp‐Ti Boundary in Carbon Nanotube/Ti Composites Prepared by High‐Pressure Torsion

Spherical aberration‐corrected high‐resolution transmission electron microscopy images reveal that Ti in the carbon‐nanotube‐reinforced‐Ti (CNT/Ti) composites synthesized via the high‐pressure torsion method has a face‐centered cubic (fcc) lattice structure. The intrinsic properties of the fcc/hexagonal close‐packed (hcp)‐Ti boundary with orientation relationships of [ 11 1 ¯] fcc //[0002] hcp and {011} fcc // { 2 1 ¯ 1 ¯ 0 } hcp between the fcc‐Ti and hcp‐Ti are revealed through a first‐principles investigation. Interface relaxation verifies that the nucleation of the fcc‐Ti structure requires a minimum stable thickness of three atomic layers. When the pressure increases, the interface adhesion work, W ad , of the fcc‐Ti ( 11 1 ¯ ) / hcp‐Ti(0002) interface decreases, the surface energy increases, and the interface bonding strength of the fcc/hcp‐Ti boundary decreases. Moreover, the hcp‐Ti(0002)/fcc‐Ti ( 11 1 − ) boundary becomes unstable under high pressure, enhancing the nucleation and growth of the fcc‐Ti phase at the boundary. The results of this study help in understanding the correlation between the inherent attributes of the fcc/hcp‐Ti boundary, and the properties of CNT titanium composites are improved.