Hetero-deformation-induced strengthening, slip activity and damage initiation of high-power laser additively manufactured Cu-Ni alloy via heterogeneous interface regulation

The main combustion chamber fabricated by Cu-Ni alloy, a key component of reusable liquid rocket engines, endures extreme high chamber pressures and intense heat fluxes. The limited insight into its interface formation mechanism, unclear strengthening pathways and uncertain damage-performance interaction mechanisms hinder practical application. This study employed a hybrid manufacturing process to fabricate GH4169/CuCrZr heterostructures via wrought substrates and laser powder directed energy deposition (LP-DED). Through a synergistic approach combining microstructural mapping, interfacial characterization, and molten pool dynamics simulations, we systematically decode the roles of Marangoni convection and solidification front subcooling in governing interface morphology evolution and transition zone development. Key findings reveal that Marangoni convection-driven hump-shaped interface morphologies significantly enhance interfacial integrity, contributing to an ultimate tensile strength of 375 MPa. In addition, hetero-deformation-induced (HDI) stress and geometrically necessary dislocation (GND) analysis further unravel the underlying strengthening mechanisms: grain-scale (GS)-GND accumulation is shown to amplify HDI stresses at interfaces between columnar and fine-equiaxed grains. Moreover, the columnar-to-fine-equiaxed grain gradient within the transition zone acts as a critical stress concentration locus, where the (1¯11)[011¯] slip system is identified as the dominant deformation mode through Schmid factor (SF) and intragranular misorientation axis (IGMA) analyses. Via the crystal plasticity-phase field damage simulations, the GH4169/CuCrZr alloy exhibits the various critical strains of damage initiation, with damage progressively evolving from grain boundaries toward the intragranular region as strain increases.