Effect of oxygen on the formability and properties of laser-directed energy deposited Ti6Al4V/316 stainless steel with V deposited layers

This study successfully fabricated Ti6Al4V/316 stainless steel dissimilar joints using laser-directed energy deposition (L-DED) with a V interlayer. The work systematically investigated the effects of process parameters and shielding atmosphere on interface formation, microstructure, and mechanical properties. It was found that argon shielding is essential to prevent oxidation and achieve defect-free deposition. Under optimized parameters (laser power 500-600 W, scanning speed 10-15 mm/s), the V interlayer effectively blocked direct interdiffusion of Ti and Fe, suppressing the formation of brittle Fe-Ti intermetallic compounds. The interface was primarily composed of a β-Ti(V) solid solution, resulting in a smooth microhardness gradient and reduced residual stress. The optimized joint achieved a maximum tensile strength of 174 MPa, with fracture occurring at the SS316/V interface. Molecular dynamics simulations further revealed that O dissolution in the FeCrNi system significantly alters its nanoindentation response: as O content increases to 1–2 at.%, the stress–indentation depth relationship shifts from an initial increase–decrease trend to a monotonic increase, providing atomistic insights into O-induced embrittlement.