Precipitation behavior of Cu–Zr compounds in a Cu-0.13 wt%Zr alloy

The microstructure of a Cu-0.13 wt%Zr alloy cast or aged at 450–950 °C for 1 min–30 days (d) after solutionizing was investigated. Spherical fine precipitates having an ordered fcc lattice with a = 0.416 nm and a cube-on-cube orientation relationship to the Cu matrix were newly found in the cast alloy. Aging the alloy at 450 and 500 °C up to 30 d produced only disk-shaped Cu5Zr precipitates. In addition to the disk-shaped precipitates, the fine ordered fcc precipitates were formed in the alloy aged at 600–850 °C for a short time. The alloy aged at 900–950 °C for 1 min showed the coexistence of the fine fcc precipitates and coarse rod-shaped Cu5Zr precipitates of the equilibrium phase. Even after prolonged aging for 7–14 d at 600–950 °C, the fine fcc precipitates still remained together with the rod-shaped Cu5Zr precipitates of the equilibrium phase, indicating that the fcc precipitated phase is fairly stable at 600–950 °C. The aging time dependences of electrical resistivity at temperatures between 600 and 950 °C allowed us to obtain the solid solubility limits at these temperatures. The obtained solvus is coincident with the data reported previously. •Precipitation behavior of Cu–Zr compounds was investigated between 450 and 950 °C.•Fine spherical precipitates with an ordered fcc lattice were newly found.•Disk-shaped Cu5Zr precipitates changed to stable rod-shaped Cu5Zr precipitates.•The solid solubility limits of Cu–Zr alloy between 600 and 950 °C were reexamined.