[SY-E9] Atomistic simulation of the deformation and crack nucleation mechanisms in titanium alloys
Titanium alloys are widely used in aero-space and chemical industries, but due to the complicated hierarchical microstructure formed in these systems, the deformation and fatigue life control is not easy. Multi-scale simulations were carried out on the deformation and microstructure evolution of titanium alloys in order to understand deformation and fatigue behavior under different conditions. The dislocation nucleation, interaction, debris accumulation and their effects on the deformation and fatigue crack nucleation were investigated. It was shown that, upon cyclic deformation, point defects and small dislocation loops can be formed in slip band by dipolar reaction. This will consume mobile dislocations, and make the operating slip system hardened; at the same time, they can provide deformation mechanism upon further increase of the stress. Comparing with perfect lattice, the lattice with point defects under tension perpendicular to the slip plane can be weakened by these point defects, therefore they may serve as fatigue crack nucleation sites and propagating paths. These understanding gained by simulations may provide important clue to the fatigue resistance design for titanium alloys.