Synergy of laser powder bed fusion (LPBF) and heat treatment for CuNi2SiCr alloy enhancement

This research explores the thermal and mechanical properties of a CuNi2SiCr alloy made by laser powder bed fusion (LPBF) for potential use in the neck insert of extrusion blow molds. Process parameter optimization, aging heat treatment design, thermal and mechanical property characterizations, microstructural analysis, and an exploration of the factors affecting thermal conductivity are presented. Results showed that the aging thermal cycle significantly enhanced the thermal conductivity of the as-build sample from ∼ 70 W/mK) to ∼ 180 W/mK. Numerical analysis of the involvement of various scattering phenomena in the overall mean free path of conducting electrons revealed that such a significant increase in thermal conductivity originated from the emergence of nanoscale Ni, Cr, and Si containing precipitates from the supersaturated matrix which depleted the matrix of extrinsic scattering sites accounting for ∼ 80 % of electron scattering in the as-built specimen. The sample subjected to heat treatment showed a 95 % increase in nanohardness and significantly higher yield strength (575 MPa) and ultimate tensile strength (687 MPa) compared to the as-built specimen (236 MPa and 291 MPa, respectively). The improvements obtained in this study in both thermal and mechanical properties showcase the potential of LPBF and subsequent heat treatment in enhancing Cu alloy materials for various industrial applications.