Analysis of β´ Cu 4 Ti Precipitation in Cu-Ti Alloys by Conventional and Diffusion-Couple Methods

An analysis of the Cu4Ti precipitation process was carried out in binary Cu-Ti alloys using the conventional method and subsequently employing a diffusion-couple based method, known as the Macroscopic-Gradient Method. The phase separation took place via the mechanism of spinodal decomposition at early stages of aging. The precipitation of the β´ (Cu4Ti) phase preceded to that of the β (Cu3Ti) phase, which is formed by cellular precipitation. The highest hardness and fastest precipitation kinetics occurred at aging of 400 and 600 °C, respectively. In the case of the macroscopic gradient method, a diffusion couple of Cu-4 wt. Ti alloys and pure copper was prepared by a diffusion annealing. This analysis enabled to determine the equilibrium and coherent lines in this alloy system. The Gibbs-Thomson equation was verified for this type of precipitation.