Powder bed fused–laser beam (PBF-LB) 70/30 copper-nickel (Cu-30Ni): Hierarchical microstructure and mechanical properties

This study explores the mechanical and microstructural characterization of powder bed fused–laser beam 70/30 CuNi (70% copper, 30% nickel), also known as Cu-30Ni, a copper-nickel alloy recently adapted for use in additive manufacturing (AM). 70/30 CuNi is a highly suitable material for applications that demand exceptional strength and high corrosion resistance in salt water at ambient and sub-ambient temperatures. Although 70/30 CuNi is traditionally fabricated through methods such as forging and casting, its application in additive manufacturing (AM) remains in its early stages, with very limited research on powder bed fused–laser beam (PBF-LB). This study addresses such a research gap by investigating the tensile strength and microstructural evolution of PBF-LB 70/30 CuNi in ( i ) as-built and ( ii ) heat-treated states, printed at different orientations. Advanced microstructural characterization tools and quasistatic uniaxial tensile tests were employed to establish a correlation between microstructure, mechanical properties (e.g., strength, ductility, and work hardening behavior), and printing orientation (i.e., vertical versus horizontal). A multi-scale hierarchical structure consists of fine cellular structures (elongated and equiaxed) within the coarse grains were identified in nano-, micro-, and macro-levels. It was observed that the horizontally built material demonstrates higher yield stress and ultimate tensile strength, but lower ductility compared to those printed in the vertical direction. We also compared our tensile results against the mechanical properties of commercial (i.e., cast) 70/30 CuNi. This study provides valuable insights into the potential of PBF-LB 70/30 CuNi as an alternative for conventionally fabricated counter material, for various industrial applications (e.g., marine). • First study linking PBF-LB 70/30 CuNi microstructure to mechanical performance. • Reveals build orientation effects on strength, ductility, and work hardening. • Post heat treatment enhances mechanical properties of PBF-LB 70/30 CuNi. • Advanced TEM/EBSD used to unveil sub-grain structures and elemental segregation.