The microstructure and formation mechanism of face-centered cubic Ti in commercial pure Ti foils during tensile deformation at room temperature

Abstract

Two variants of face-centered cubic (fcc) Ti phase appear in ultra-thin commercial pure Ti foils with hexagonal closed packed (hcp) structure during tensile deformation at room temperature. The orientation relationship between fcc-Ti phase and hcp-Ti matrix is determined as 〈0001〉HCP//〈001〉FCC, 〈112¯0〉HCP//〈11¯0〉FCC and 〈011¯0〉HCP//〈110〉FCC. The fcc-Ti phase with a habit plane of {011¯0}HCP usually nucleates at grain boundary and grows along the direction of 〈112¯0〉HCP. The thickness of fcc-Ti phase with a shape of thin plate ranges from 10nm to 200nm. Dislocations, steps and stacking faults with a space of 0.58nm can be seen in fcc-Ti. The formation of a five-layer fcc-Ti can be accomplished by the formation of stacking faults and gliding of 1/6[112¯0] Shockley partial dislocations on the prismatic plane of hcp-Ti. The 1/3[112¯0] dislocations in hcp-matrix can cross the fcc-Ti phase because the Burgers vector of these dislocations is coincidence with 1/2[110] dislocations in the fcc-Ti.