1989 Volume 30 Issue 2 Pages 127-136
The dilute Cu–Si, Cu–Si–Ti and Cu–Si–Zr alloys were internally oxidized in the temperature range of 973–1323 K. The crystal structures of dispersed oxides in the internally oxidized alloys were identified by X-ray diffractometry. The measurements of mean particle sizes, analysis of dispersed particles and the observation of precipitate morphology were carried out with an analytical transmission electron microscope. The hardness measurements were performed using a micro-Vickers hardness tester.
The oxide particles in the internally oxidized Cu–Si binary alloys were initially dendritic and subse-quently transformed to spherical in process of time. By addition of Ti and Zr into the Cu–Si alloy, the dispersed oxide particles became remarkably finer. The oxide phase in the internally oxidized Cu–Si alloys in the temperature range of 973–1073 K was amorphous SiO2, but at 1173–1323 K α-cristobalite was precipitated in addition to amorphous SiO2. The amount ratio of α-cristobalite to amorphous SiO2 was increased with increasing oxidation temperature. The dispersed oxide phases in the internally oxidized Cu–Si–Ti alloy were amorphous SiO2 and rutile-type TiO2, and in the Cu–Si–Zr alloy amorphous SiO2, monoclinic ZrO2, tetragonal ZrO2 and ZrSiO4 were precipitated. Pairs of SiO2 and TiO2, or SiO2 and ZrO2 were formed in the ternary alloys. The oxide particles precipitated in the ternary alloys were finer than those in the binary alloys. The effect of Zr on refining dispersed oxide particles was greater than that of Ti. The hardness values of internally oxidized ternary alloys were higher than those of binary alloys.
