Diffusion-controlled growth mechanism of phases and the microstructural evolution in the Ni-Zn system

Abstract

The diffusion-controlled growth mechanism of the phases and microstructural evolution in correlation to estimated diffusion coefficients are described in solid Ni-solid Zn and solid Ni-liquid Zn diffusion couples that mimic the hot-dip galvanization of Ni pre-coated steel. Contrary to earlier belief, the location of the Kirkendall marker plane is detected not at the δ-NiZn8/Zn interface but inside the δ-NiZn8 phase indicating the role of both the diffusing elements Ni and Zn on the evolution of duplex morphology in this phase. Further, the growth of γ1-NiZn3, and γ-Ni2Zn11 phase layers with distinct microstructures are identified contrary to the belief that there is only one intermediate phase γ-Ni2Zn11 over this composition range. This study explains the role of relative mobilities of the elements behind the characteristic microstructural evolution in this system of technological importance.