Evolution of the Microstructures and Properties of Cu‐xCr‐0.4Nb Alloys

The microstructures and properties of Cu‐ x Cr‐0.4Nb alloys were investigated by changing Cr composition and cooling mode. The as‐cast microstructures and fracture morphologies were observed by SEM. The morphology and size of the precipitated phase were observed by TEM. The hardness, electrical conductivity, and tensile strength of the resulting alloys were also tested. For Cu‐ x Cr‐0.4Nb alloys cooled in furnace, Cr 2 Nb particles were formed near the eutectic regions, and destroy the continuity of the eutectic regions. The Cu–Cr–Nb alloys casted in copper mold can significantly increase the solid solubility of solute elements. The microstructures are finer cellular crystals without the segregation of Cr 2 Nb particle. It makes the microstructures more homogeneous and greatly improves the hardness. After aging, Cr and Cr 2 Nb particles with the scale of 5 ≈ 10 nm were precipitated in the copper matrix. The hardness, conductivity and tensile strength can reach to 142HB, 90.52% International Annealed Copper Standard (IACS) and 427 MPa, respectively. In addition, after the alloy being softened, the Cr 2 Nb particles were found near the Cr particles by TEM, which inhibited the high‐temperature coarsening of precipitated Cr phase. The softening temperature of Cu‐1.0Cr‐0.4Nb alloy reaches 600 °C.