An experimental study on the interdiffusion behaviors and mechanical properties of Ni-Zr system

We have investigated the interdiffusion behaviors and mechanical properties of Ni-Zr intermetallic compounds formed in the Ni-Zr interdiffusion interface zone at a temperature range of 865-955 °C. Eight intermetallic compounds (Ni5Zr, Ni7Zr2, Ni3Zr, Ni21Zr8, Ni10Zr7, Ni11Zr9, NiZr, and NiZr2) have been observed in the Ni-Zr diffusion zones. The square of the thickness of the formed intermetallic compounds linearly increases with time, which indicates that the growth of intermetallic compounds is diffusion-controlled at long-term annealing. The decomposition temperature of the Ni11Zr9 has been confirmed at a temperature range of 930-935 °C. Interdiffusion coefficients and activation energies are obtained from the measured composition profiles. We found that the Young's modulus decreases with the increase of Zr concentration, where Ni5Zr has the highest Young's modulus of 250.21 GPa and NiZr2 has the lowest value of 76.82 GPa. However, without any linear relation to the concentration of Zr, the Ni10Zr7 has the highest hardness as 10.17 GPa, and NiZr2 has the lowest hardness as 5.56 GPa.