Microstructure evolution and mechanical behaviors of Ti6Al4V/NbZr1 bimetallic additively manufactured structure: A molecular dynamics simulation

Understanding atomic-scale evolution is critical to tailoring the mechanical behavior of bimetallic materials in additive manufacturing. In this study, we apply molecular dynamics (MD) simulation to investigate the microstructural and mechanical evolution of Ti6Al4V/NbZr1 bimetallic structures fabricated using wire arc additive manufacturing (WAAM) under low, medium, and high heat input conditions: 180 Ampere (LHI), 200 A (MHI), and 220 A (HHI), respectively. An eight-layer deposition model was simulated to analyze phase transformation, grain growth, dislocation behavior, and interface diffusion. Results indicate that higher heat inputs promote greater atomic mobility and interfacial mixing, leading to increased cluster formation and amorphization, while lower heat inputs yield finer grains and higher tensile strength. Transverse tensile specimens consistently showed higher strength than longitudinal ones, attributed to directional microstructural effects. This work provides atomic-level insights into the relationship between thermal input and microstructure-property correlations in WAAM-fabricated bimetallic systems.