Effects of heat treatment processes on the microstructures and properties of powder metallurgy produced Cu-Ni-Si-Cr alloy

To obtain optimal microstructures and properties of a powder metallurgy produced (P/M) copper alloy, this research designed a series of solution and aging heat treatment parameters for a P/M Cu-7.4Ni-1.3Si-1.2Cr alloy. After heat treatment, the variation in their microstructures, thermal properties and mechanical properties were investigated. The microstructure analysis suggested that the hardness or tensile strength increased after an aging heat treatment due to the large number of nanometer-sized precipitates of beta-Ni3Si and delta-Ni2Si phases that were formed. The optimal heat treated P/M copper alloy (8-h solution heat treatment at 970 degrees C followed by 6-h aging at 450 degrees C) had an extremely good combination of an average sub-grain size (<30 mu m), an average tensile strength (up to 820 MPa) and an average thermal conductivity (110 W/mK), which offers possibilities for application in mold tooling. (C) 2014 Elsevier B.V. All rights reserved.