Reaction Diffusion in the Cu-Hf System

Reaction diffusion between pure Cu and Hf was studied in the temperature range from 1023 to 1223 K. Formation of six intermetallic compounds, Cu5Hf, Cu4Hf, Cu7Hf2, Cu3Hf, Cu3Hf2 and CuHf2, was observed in the diffusion zone.The layer thickness of these intermetallic phases, except Cu7Hf2 above 1173 K, was found to increase obeying the parabolic law, showing that the growth of phase layers was controlled by diffusion process. The temperature dependence of the growth rate constants of the Cu5Hf, Cu4Hf, Cu3Hf and CuHf2 phase layers satisfied the Arrhenius relationships. However, above 1173 K that of the Cu7Hf2 and Cu3Hf2 phase layers deviated downward from the Arrhenius relationship; the deviation was attributed to the growth of Cu3Hf phase and the transition of the Cu7Hf2 phase to the Cu4Hf phase at higher temperatures.