Microstructure and properties of Cu-Cr and Cu-Cr-Mg alloys under different processing conditions

Abstract

Abstract Cu-0.5Cr (wt%) and Cu-0.5Cr-0.1Mg (wt%) alloys were manufactured in this study to analyse the relationship between the physical properties and microstructure under different states. Optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to observe the microstructures of the alloys following homogenization, hot-rolled, solid solution, cold-rolled and aging. The results showed that insoluble Cr phases existed in copper chromium and copper chromium magnesium alloys after holding at 925°C for 12 h for homogenization and hot rolling deformation of 80%, and Mg elements prevented the segregation of Cr phases at grain boundaries. After solution treatment by holding at 1000°C for 1 h, the mean grain size of both alloys were 299 nm and 81 nm, respectively, and the volume fraction of undissolved Cr phase was 0.4% and 0.2%, respectively. After 60 % cold deformation treatment, the hardness of the two alloys increased significantly as a result of the work hardening caused by the generation of dislocation. In the aging stage of 450°C for 1 h, lots of Cr precipitates were found in Cu-0.5Cr and Cu-0.5Cr-0.1Mg alloys, with a corresponding hardness of 162.8 HV and 170.1 HV and electrical conductivity of 82.9% IACS and 77.8% IACS, respectively.