Electron microscope observations on precipitation in a Cu−1.07% Zr alloy

Abstract

The nature of precipitation was studied in a strip of a high-purity Cu−1.07% Zr alloy, solution treated at 950°C. Stacking faults were generated during aging at 500°C, associated with bands of fine-precipitate platelets and tended to disappear at long aging time. The mechanism of generation of these faults is discussed. No faults were observed if the alloy was cold-rolled 40% prior to aging at 500°C. Instead, very fine-precipitate platelets formed at dislocations and recrystallization was absent even after 48 h aging. Partial recrystallization occurred on aging 1 h at 650°C, complete after 5 min at 750°C or 850°C. The precipitate platelets were parallel to {111} matrix planes and showed no evidence of coherency strain fields. They were thought to be the Cu 5Zr equilibrium phase. X-Ray d-values were obtained on particles extracted from a hot-rolled Cu−10.2% Zr alloy.