The mechanical coupling effect of α and β phases in Ti6Al4V alloy undergoing laser shock peening: A molecular dynamics study

In the dual- or multi-phase metallic materials, the influence of different microstructural constituents on the plastic strain/stress distribution is still an area of great controversy. Herein, the heterogeneous deformation behavior of alpha and beta phases in Ti6Al4V duplex titanium alloy undergoing laser shock peening (LSP) has been investigated by molecular dynamics simulations, and the corresponding typical microstructural features are characterized at varied strains. Also, the relationship between the theoretical microstructural morphologies and the micro stress is revealed. It evidently indicates that, the grain refinement process can be summarized as: (i) dislocation motions1 interacting with deformation twins in alpha phases, (ii) a combination of dislocation propagations and the deformation-induced phase transition from beta phase to alpha phase. In addition, unlike the alpha singlephase titanium alloy, the representative stress - strain curve of alpha + beta titanium alloy presents a gentle fluctuation trend with smaller amplitude value, suggesting an occurrence of the coupling deformation behavior between alpha and beta phases. The initial interfacial dislocation nucleation prefers to site in the alpha/alpha interface rather than the alpha/beta interface, then emitting to the interior of alpha grains. Features of dislocation slip, twin growth, stacking fault, and phase transformation dominate the release of LSP-generated micro stress, while grain and interphase boundaries, as well as dislocation locks, contribute to the increment of the LSP-generated micro stress.