Reaction Diffusion in the Cu-Hf System

Abstract

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.