LAUSR

Abstract 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.