Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1584437 | Materials Science and Engineering: A | 2007 | 9 Pages |
In order to examine experimentally the kinetics of the reactive diffusion between solid Cu and liquid Al, Cu/Al diffusion couples were isothermally annealed in the temperature range between T = 973 and 1073 K. Owing to annealing, compound layers consisting of the β, γ1 and ɛ2 phases are produced between the Cu-rich solid (α) and Al-rich liquid (L) phases. The β, γ1 and ɛ2 phases are the only stable compounds at T = 973–1073 K. The mean thickness of each compound layer is proportional to a power function of the annealing time. For the β layer, the exponent of the power function is close to 0.5 at T = 1023–1073 K, but nearly equal to 0.25 at T = 973 K. On the other hand, for the γ1 layer, the exponent takes values between 0.25 and 0.5 at T = 1023–1073 K, but that smaller than 0.25 at T = 973 K. The exponent smaller than 0.5 indicates that grain boundary diffusion predominantly controls the growth of the compound layer and grain growth occurs at a certain rate. In contrast, the ɛ2/L interface migrates towards the α phase. The migration distance of the ɛ2/L interface is much greater than the total thickness of the compound layers, and proportional to the square root of the annealing time. Consequently, the migration of the ɛ2/L interface is governed by interdiffusion in the L phase. According to estimation, the interdiffusion coefficient is much greater for the L phase than for the solid phases. As a result, the ɛ2/L interface migrates towards the α phase, and the migration rate of the interface is much greater than the overall growth rate of the compound layers.