Liquid Metal Embrittlement (LME) cracks at Cu/Austenitic Stainless Steel (ASS) interfaces during additive manufacturing compromise structural reliability. This study proposes a novel strategy to suppress LME cracks by controlling the solidification mode of austenitic stainless steel through interfacial alloying. Using Laser-Directed Energy Deposition (LDED), Ti1 (1wt% Ti6Al4V + 316L) and Ti3 (3wt% Ti6Al4V + 316L) interlayers were introduced between the 316L substrate and CuSn10 deposited layer. While control samples (no interlayer) show severe LME cracks, Ti1/Ti3 interfaces remain crack-free. Thermodynamic calculations and microstructure analysis reveal Ti6Al4V addition shifts 316L’s solidification mode from Austenitic (A) to Austenitic-Ferritic (AF) or Ferritic-Austenitic (FA). Molten pool convection further promotes FA/F modes in the fusion zone, blocking liquid Cu penetration along grain boundaries. Ti-rich precipitates segregate in Cu-rich regions, reducing liquid Cu mobility and stress concentration. Tensile tests confirm fractures occur solely in CuSn10 deposits, indicating robust interfacial bonding strength. This interfacial alloying strategy enables crack-free, high-reliability Cu/steel heterostructures in additive manufacturing.
Sun et al. (Sun,) studied this question.