Diffusion Kinetics in Mg-Cu Binary System

The solid-solid interfacial reaction in the Mg-Cu binary diffusion couples was studied at temperatures of 673, 703 and 733 K, with reaction time ranging from 24 to 72 h. MgCu2 and Mg2Cu were formed between Mg and Cu matrixes at the studied temperatures. The growths of MgCu2 and Mg2Cu followed the parabolic kinetics, which suggests that the growth of the two phases is controlled by bulk diffusion mechanisms. The activation energies for growths of MgCu2 and Mg2Cu were determined to be 147.57 +/- 1.49 and 139.12 +/- 1.30 kJ/mol, respectively. The interdiffusion coefficients were evaluated as functions of compositions in MgCu2 and Mg2Cu intermetallic phases at the studied temperatures, which were further utilized for evaluating the activation energies and frequency factors for interdiffusion in each phase. The Mg impurity diffusion coefficient in Cu was higher than the Cu impurity diffusion coefficient in Mg. The activation energy and pre-exponential factor for diffusion of Mg impurity in Cu were determined to be 139.38 +/- 0.65 kJ/mol and 1.02(+/-0.26) x 10(-4) m(2)/s, respectively, while those for diffusion of Cu impurity in Mg were determined to be 164.04 +/- 7.18 kJ/mol and 3.10(+/-0.31) x 10(-3) m(2)/s, respectively.