Tensile Properties, Micro-computed Tomography Defect Analysis, and Milling Performance of As-Built and Heat-Treated CuCrZr Parts Fabricated by Laser Powder Bed Fusion

Abstract

Copper–chromium–zirconium (CuCrZr) is an age-hardenable copper alloy valued for its rare mix of high strength and thermal conductivity, making it a logical choice for heat sinks, divertor parts, and rocket-engine liners. Laser powder bed fusion (LPBF) can fabricate such parts with internal cooling channels that are difficult to machine conventionally; however, this process makes the alloy a bit softer and may eventually lead to the formation of internal pores or voids. This study focuses on how LPBF CuCrZr behaves, both mechanically and during milling, in the As-Built (AB) and heat-treated states. Vickers hardness rose from about 118 HV in the AB state to 152 HV after heat treatment. Tensile testing demonstrated the ultimate tensile strength improving from roughly 680–700 MPa to 780–820 MPa, a gain of about 15–18%, while total elongation remained at or above 95% for all heat- treated specimens. Micro-computed tomography (μCT) confirmed a dense build in both states, with relative density near 99% and no lack-of-fusion defects or cracking; only a few small, isolated gas pores were seen. In milling, the harder, heat-treated material required slightly higher cutting forces (CF) but produced a more stable cut and better surface finish, with the lowest 3D roughness at high cutting speed (CS) and low feed. Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) were used to characterize the microstructural, compositional, and surface-topographical changes, respectively, observed after heat treatment. Consequently, the heat treatment strengthens LPBF CuCrZr and improves surface finish without compromising the soundness or ductility.