Enhanced strength-thermophysical synergy of directed energy deposition-arc manufactured Inconel-Copper bimetallic via cooperative heat treatment

Achieving a synergistic balance between strength and service-related thermophysical properties remains a significant challenge in structural material. This study addresses this issue by employing cooperative heat treatment strategies to optimise Inconel-copper bimetallic structures fabricated via Directed Energy Deposition-Arc (DED-Arc). Phase diagram calculations guided the design of these heat treatments. Comparative analyses revealed that the solution plus aging treatment (STA2#) achieved a balance between high strength and ductility with a tensile strength of 342.4 MPa and an elongation of 22.2%, while maintaining excellent thermal conductivity. Digital image correlation revealed localised deformation in the C18150 region, and the improved mechanical properties were attributed to grain boundary and precipitation strengthening. The thermophysical properties were significantly improved by the designed cooperative heat treatment, with the thermal conductivity of the STA2# bimetallic ranging from 41.16 to 56.08 W/(mk) over a temperature range of 30 to 310°C, approximately 13% improvement than the as-fabricated sample. This improvement in thermal conductivity resulted from the decomposition of the supersaturated solid solution. This study provides a promising heat treatment strategy for advancing Inconel-copper bimetallic in next-generation rocket engine potential application.