Interfacial Evolution and Bonding Mechanisms in γ-TiAl/Al Explosive Welding: A Molecular Dynamics Study.

The explosive welding (EXW) of γ-TiAl to Al offers a promising route to fabricate lightweight, high-strength hybrid structures, yet the atomic-scale bonding mechanisms remain unclear. In this work, large-scale molecular dynamics simulations were performed to investigate the effects of flyer velocity (1.5-2.9 km s⁻¹) and collision angle (10-40°) on the thermal response, diffusion behavior, phase evolution, and mechanical performance of γ-TiAl/Al EXW. Increasing flyer velocity drives a transition from solid-solid contact to solid-liquid and ultimately liquid-liquid mixing, accompanied by elevated interfacial temperature, thicker diffusion layers, and extensive amorphization. During cooling, the Al base exhibits strong FCC recrystallization but retains vacancy defects, whereas the γ-TiAl flyer preserves stable HCP bands and quenched disorder. Mechanical tests reveal that a flyer velocity of 2.5 km s⁻¹ achieves the best strength-ductility balance (~5.1 GPa peak stress, ~0.08 fracture strain) through the formation of a well-mixed interface. At this velocity, increasing the collision angle from 10° to 30° gradually improves joint strength and ductility by promoting more uniform defect evolution and plastic deformation, whereas an excessive angle (40°) induces shear-driven separation that weakens bonding. These findings elucidate the fundamental atomic processes governing γ-TiAl/Al EXW and provide quantitative guidance for optimizing processing parameters in advanced lightweight structural applications.