Multiscale investigation of precipitate-dislocation interactions in additive manufacturing: a coupled phase-field and thermal stress dynamics approach

Non-equilibrium solidification during NiTi alloys manufacturing via Laser Beam Powder Bed Fusion (PBF-LB), induces dendritic morphologies and heterogeneous precipitate distribution. However, the underlying mechanisms governing dislocation interactions remain poorly understood. An improved phase-field model coupled with melt pool temperature field is proposed to simulate the impact of dendritic growth behavior on precipitate distribution under spatiotemporal variations of temperature gradient (G) and solidification rate (R). Additionally, this study proposes a volume-conserved deformation scheme that couples the phase-field crystal (PFC) method with a thermal-stress dynamics model to simulate the influence of precipitates on dislocation motion. The results reveal that reduced volumetric energy density enhances cooling rates, decreasing primary dendrite arm spacing (PDAS), mitigating elemental segregation, and refining Ti2Ni precipitates with homogeneous grain boundary dispersion. Uniformly dispersed precipitates shorten dislocation recovery time and increase pinning probability at phase interfaces, resulting in effectively hindering dislocation glide while promoting multiplication and entanglement. This leads to high-density disordered dislocation networks, contrasting with well-defined dislocation cells formed under high energy density.