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

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), <11<(2)over bar>0>(HCP) // <1<(1)over bar>0>(FCC) and <01<(1)over bar>0>(HCP) // <110> (FCC). The fcc-Ti phase with a habit plane of {01 (1) over bar0}(HCP) usually nucleates at grain boundary and grows along the direction of <11<(2)over bar>0>(HCP). The thickness of fcc-Ti phase with a shape of thin plate ranges from 10 nm to 200 nm. Dislocations, steps and stacking faults with a space of 0.58 nm 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[11 (2) over bar0] Shockley partial dislocations on the prismatic plane of hcp-Ti. The 1/3[11 (2) over bar0] 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.