Effects of minor rare earths on the microstructure and properties of Cu-Cr-Zr alloy

The effects of minor rare earths, such as Sc, Er, and Y, on the microstructure and properties of Cu-Cr-Zr alloys, were studied systematically. Microstructure evolutions and properties variations of Cu-Cr-Zr-(X) alloys indicate that the hot-rolling + solid solution treatment + cold-rolling + aging treatment is an appropriate method to fabricate studied Cu-Cr-Zr-(X) alloys with high ultimate tensile strength, high electrical conductivity, excellent plasticity, and large strength-elongation products. The addition of Y effectively suppressed the precipitation and growth of Cr particles in the Cu-Cr-Zr-Y alloy. The high-temperature ultimate tensile strength of the peak-aged Cu-Cr-Zr-Y alloy was 381 MPa at 450 °C, and that of the over-aged one was 341 MPa, which are much higher than those of the Cu-Cr-Zr alloy in the peak-aged temper (320 MPa) and the over-aged temper (300 MPa). The primary strengthening mechanism in the high strength Cu-Cr-Zr-Sc alloys is the grain boundary strengthening following the Hall-Petch relationship. The mainly strengthening mechanisms in the Cu-Cr-Zr, Cu-Cr-Zr-Y, and Cu-Cr-Zr-Er alloys are precipitation strengthening and dislocation strengthening. These findings indicate rare earth elements play important roles in improving the high/room temperature properties of Cu-Cr-Zr system alloys.