Microstructures and electrical and mechanical properties of Cu-Cr alloys fabricated by selective laser melting

In this study, the microstructures and electrical and mechanical properties of Cu-1.3 mass%Cr (1.3Cr) and Cu-2.5 mass%Cr (2.5Cr) alloy specimens fabricated by selective laser melting (SLM) were investigated. The effects of heat treatment on the microstructures and properties of the SLM specimens were also studied. Cu-Cr SLM specimens with a relative density of >99.7% were obtained. By annealing at 600 °C, the electrical conductivity of the SLM specimens significantly increased to maximum values of 91% IACS and 73% IACS for the 1.3Cr and 2.5Cr SLM specimens, respectively. Further, by annealing at 450 °C, the tensile strength and Vickers hardness of the SLM specimens also increased, with the tensile strength reaching maximum values of 640 and 777 MPa for the 1.3Cr and 2.5Cr SLM specimens, respectively. A close relationship was found between the changes in the properties and the nanostructures. By annealing, a fine Cr phase precipitated from the supersaturated solid solution, which formed through rapid solidification by local laser irradiation. Therefore, the electrical conductivity increased because of the decrease in the solid-solute Cr. Meanwhile, the SLM specimens were strengthened because of age hardening by the precipitation of the fine Cr phase.