Diffusional behaviors and mechanical properties of Ni-Zn system

Abstract

In this paper, the solid-solid diffusion reaction and growth kinetics of Ni-Zn system were investigated using diffusion couple technique. Three intermetallic compounds (IMCs), β1 (NiZn), γ (Ni2Zn11) and δ (Ni3Zn22) were observed at the diffusion zone with the annealing temperature range between 598 K and 673 K. The results indicate that the growth process of reaction zone was dominated by volume diffusion. And the growth constants, integrated diffusion coefficients, growth activation energies and diffusion activation energies of γ and δ were evaluated based on thickness of the phases, reaction temperatures and annealing times. The Young’s modulus and Vickers hardness of the three phases were evaluated from the displacement-loading curve by nanoindenter testing. The Young's modulus and hardness of the IMCs increased firstly and then decreased with the increasing of Zn concentration, where γ phase has the highest Young's modulus (183.3 GPa) and highest hardness (6.05 GPa) among the three phases. Finally, the bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (v) of the Ni-Zn IMCs were calculated by the first-principles calculations. The tendency of calculated Young's modulus varying with the composition of Zn was consistent with that of experimental results.