Interfacial reaction between solid nickel and liquid zinc

Abstract

Interfacial reactions between solid nickel and liquid zinc at 450-650 ℃ for 30-600 s were studied. The morphology and growth behavior of intermetallic compound layers at the interface between solid nickel and liquid zinc were observed and analyzed by SEM and EDS. The results show thatγand δ phases are formed at 450 ℃ at the Ni/Zn interface, and at 550 and 650 ℃ ℃ onlyγphase is formed at the interface and someδ phase particles will be participated during solidification on the surface ofγphase layer. Theβ 1 phase is absent under experimental conditions. Many cracks occur in the layers due to the difference in thermal expansion coefficients of these phases. It is found that the kinetics of the intermetallic compounds growth follows a parabolic law of time, as controlled by the diffusion mechanism. The apparent activation energies are 113.9 kJ/mol for the growth ofγphase and 125.87 kJ/mol forγ 1 phase, respectively.

Compound Growth due to Reactive Diffusion between Solid-Ni and Liquid-Zn

“…6. On the other hand, as mentioned in Section 1, the reactive diffusion between solid Ni and liquid Zn was experimentally observed by Kong et al 39) In their experiment, Ni/Zn diffusion couples were prepared by an immersion technique and then isothermally annealed at temperatures of T = 723923 K. An intermetallic layer consisting of the £ and ¤ phases formed at the original interface in the Ni/Zn diffusion couple at T = 723 K. At T = 823923 K, however, the ¤ phase was not detected in the intermetallic layer. Their values of the layer thickness l for T = 923 K are plotted against the annealing time t as open squares in Fig.…”

“…where K is the parabolic coefficient with a dimension of m 2 /s. The values of K reported by Kong et al 39) are shown as open squares in Fig. 7.…”

“…Within the experimental annealing times, l is slightly smaller for the dashed line than for the solid line, and n is lightly greater for the dashed line than for the solid line. Since n is close to 0.5 for the dashed line, it is assumed by Kong et al 39) that a parabolic relationship holds between l and t as follows:…”

“…As previously mentioned, an immersion technique was used to prepare Ni/Zn diffusion couples by Kong et al 39) In their experiment, each solid Ni wire specimen with diameter of 1 mm and length of 50 mm was immersed in molten Zn with T = 723923 K in an open chamber fulfilled with Ar gas. During immersion, the following reactions may occur in the open chamber.…”

“…In contrast, the reactive diffusion between solid Ni and liquid Zn was experimentally observed by Kong et al 39) in the temperature range of T = 723923 K. In their experiment, however, an immersion technique was used to prepare Ni/Zn diffusion couples. At T = 723 K, an intermetallic layer composed of the £ and ¤ phases formed at the original interface in the Ni/Zn diffusion couple.…”