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.