A study on the mechanical and electrical properties of high-strength CuCrZr alloy fabricated using laser powder bed fusion

Abstract

Copper-chromium-zirconium (CuCrZr) is tailored using additive manufacturing, particularly laser powder bed fusion (LPBF). Due to high thermal conductivities and high reflectivity of infrared laser irradiation, it is still challenging to fabricate copper alloys using the LPBF technique. To address the issue, a short wavelength laser (515 nm) was employed in the LPBF process. In this work, the CuCrZr alloys were built with optimized building parameters such as powder of 485 W, scanning speed of 400 mm/s, and hatching distance of 0.09 mm. The relative density of the samples was found to be 98.07 %. The as-built samples exhibit good mechanical properties with ultimate tensile strength (UTS) of 447 ± 13 MPa, yield strength (YS) of 400 ± 11 MPa, total failure elongation (EL) of 10 ± 3 %, and Vickers hardness of 130 ± 15 HV). However, the electrical property is poor with 30 ± 1 %IACS. The high tensile stress and low electrical conductivity may attribute to the dislocation cells. Moreover, the dissolved Cr atoms result in poor conductivity. By direct aging treatment at 500 °C for 1 h, excellent mechanical properties (UTS = 566 ± 18 MPa, YS = 487 ± 13 MPa, EL = 15 ± 1 %, Vickers hardness = 161 ± 15 HV) were achieved while maintaining a good conductivity (64 ± 3 % IACS). The main contribution to the increase in YS is attributed to (I) the nanoscale Cr precipitated homogeneously in the copper matrix during the direct aging treatment and (II) the remaining high dislocation density near the dislocation cells. The enhancement of the electrical conductivity is attributed to the decomposition of the supersaturated solid solution.