Growth Behavior Of Compound Layers Research Articles

Effect of High Magnetic Field on Growth Behavior of Compound Layers during Reactive Diffusion between Solid Cu and Liquid Al

The effect of magnetic field on the growth behavior of compound layer was examined at the interface between the solid Cu and liquid AI during reactive diffusion. It was found that the thickness of compound layer was reduced by the high magnetic field. The growth activation energy in β, γ 1 and ɛ 2 layers under a high magnetic field was larger than those in non magnetic circumstances, the increment percentage being 4.8%, 13.3% and 5.5%, respectively.

Growth behavior of compound layers during reactive diffusion between solid Cu and liquid Al

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, γ 1 and ɛ 2 phases are produced between the Cu-rich solid (α) and Al-rich liquid (L) phases. The β, γ 1 and ɛ 2 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 γ 1 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 ɛ 2/L interface migrates towards the α phase. The migration distance of the ɛ 2/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 ɛ 2/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 ɛ 2/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.

Growth behavior of compound layers in Sn/Cu/Sn diffusion couples during annealing at 433–473 K

The kinetics of the reactive diffusion between Cu and Sn at solid-state temperatures was experimentally examined using Sn/Cu/Sn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed at temperatures between T = 433 and 473 K for various times in an oil bath with silicone oil. Due to annealing, compound layers consisting of Cu 3Sn and Cu 6Sn 5 are formed at the Cu/Sn interface. In most of the annealed diffusion couples, grains of CuSnO exist in the Cu 6Sn 5 layer. However, the CuSnO grain scarcely influences the growth behavior of the compound layers. The thickness of the Cu 6Sn 5 layer is around twice greater than that of the Cu 3Sn layer. The difference between their thicknesses slightly increases with increasing annealing temperature. At a constant temperature, the ratio of the thicknesses remains constant independent of the annealing time. The total thickness l of the compound layers monotonically increases with increasing annealing time t according to equation l = k( t/ t 0) n , where t 0 is unit time, 1 s. The observations provide n = 0.37, 0.43 and 0.50 at T = 433, 453 and 473 K, respectively. The value n = 0.5 indicates that the volume diffusion is the rate-controlling process for the reactive diffusion at T = 473 K. As the annealing temperature decreases, the grain boundary diffusion will contribute to the rate-controlling process. Thus, the values of n smaller than 0.5 yield that there is the contribution of the grain boundary diffusion and the grain growth occurs at certain rates at T = 433 and 453 K. Since the ratio between the thicknesses of the compound layers is kept constant during isothermal annealing, the same rate-controlling process is expected to work in both compound layers.