Characterization of Microstructure and Mechanical Properties of CuCr Alloy Produced by Stir Casting

Abstract

The relatively low mechanical properties of pure copper at low and high temperature made it very limited applications. The mechanical properties of the copper can be improved by adding a small amount of elements such as Cr. This work consists of four CuCr alloy castings (0.3, 0.8, 1.2 and 1.5%) by using the stir casting method in an argon atmosphere. Then, the heat treatment was done for these alloys which included solution treatment and aging. Heat treatment was treated at 980 ° C for 1 hour, then water-quenching, followed by an aging treatment at 480 ° C for 2.4 and 6 hours. The Optical Microscopy and the Scanning Electron Microscopy (SEM) with  (EDS) were used to study the microscopic structure of the produced alloys. The results showed that the mechanical properties of copper increased with increasing chromium content. The microstructure of the castings consist of  the dendiritic structure, columinar and segregation. It has been also indicated that after heat treatment and aging, the microstructure changed to fine grains and the clusters disappeared. XRD showed a α-Cu phase and a small amount of CrO2 in microstructures. The highest value of hardness and the ultimate tensile were 101 Hv and 239.12 MPa, respectively. They were achieved at 1.5wt% addition of Cr at 480oC and 4hrs aging