Kinetics of Solid-State Reactive Diffusion in the Cu/Zn System

Abstract

The kinetics of the solid-state reactive diffusion between pure Cu and Zn was experimentally examined using sandwich Zn/Cu/Zn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed in the temperature range of 523-623 K for various times up to 49 h. Owing to annealing, an intermetallic layer consisting of the γ and ε phases was formed at the original interface in the diffusion couple, where the thickness is much smaller for the ε phase than for the γ phase. The total thickness of the intermetallic layer increases in proportion to a power function of the annealing time. The exponent of the power function takes values of 0.60-0.62 at 523-623 K. These values of the exponent indicate that volume diffusion predominantly controls the layer growth and interface reaction partially contributes to the rate-controlling process.

Study of Reactive Diffusion in Cu/Zn Diffusion Couple

“…The absence of this phase may be due to difficulties of nucleation and/or to reactions at its boundaries canceling the total growth rate of the phase. These results are consistent with those of previous studies of solid-state reactive diffusion carried out on Cu/Zn couples isothermally annealed at temperatures in the range 250-350 • C (12)(13)(14) .…”

“…Cu/Zn couples prepared by diffusion bonding technique and then annealed at 300, 300, 350 and 380 • C (12) and diffusion couples investigated at 350 • C (13) indicated the formation at the Cu/Zn interfaces of only ε and γ phases. Cu/Zn couples prepared by the bonding technique and then annealed at temperatures in the range 250-350 • C showed the formation of only the ε and γ phases and that the growth kinetics of both phase layers were not parabolic (14) . On the other hand, diffusion couples investigated at temperatures ranging from 290 • C to 380 • C showed that, at all the studied temperatures, β , γ and ε phases form at the Cu/Zn interface and grow parabolically with annealing time (15) .…”

Growth Behavior of Compounds during Reactive Diffusion in the Solid-Cu/Liquid-Sn System

“…If interface reaction governs the layer growth, n is equivalent to unity. [37][38][39][40][41][42][43][44][45][46][47][48][49][50] As previously mentioned, the δ-Cu 4 Sn layer grows mainly into the Cu. Thus, the migration rate is greater for the Cu/Cu 4 Sn interface than for the Cu 4 Sn/Cu 3 Sn interface.…”