Molecular dynamics simulations of TC4 titanium alloy with mechanical property calculations after various heat treatments

This work explores the relationship between the microstructure and mechanical properties of TC4 titanium alloy using molecular dynamics simulations. The stress-strain curves are calculated from tensile and shear tests. For the TC4 model with initial HCP structure, tensile strength along the [0001] crystal direction is larger than along the [01-10] and [2-1-10] directions. The tensile strength also increases with larger strain rate. During tensile deformation, phase transformation from HCP to BCC structure is observed, which is caused by dislocations along the close-packed direction [-1-120]. A band of amorphous structure is formed in the middle of shearing, which causes the abrupt drop in shear stress. By setting a temperature control, the heating, holding and cooling stages of heat treatment are simulated to mimic the impact of annealing, solid solution and aging. The results confirm a general trend of improved tensile and shear strength with annealing and additional solid solution and aging. With higher solid solution temperature, the amount of α phase also increases, giving rise to higher tensile and shear strength simultaneously. At the same 811 K for aging, shear strength also increases with solid solution temperature. But at the same 1227 K for the solid solution, shear strength decreases with aging temperature, in agreement with experimental results.