Diffusion study in BCC Zr–Nb–Ti ternary alloys

Abstract

Analyzing diffusion behaviors can help in predicting the relevant properties of Zr alloy materials. In this work, the diffusion behaviors of the BCC Zr–Ti–Nb system were studied via the diffusion couple method. Based on the concentration-distance profiles analytically represented by the error function expansion (ERFEX), the ternary inter-diffusion coefficients and impurity diffusion coefficients of Zr–Ti–Nb alloys were extracted using the Whittle–Green method and Hall methods. By comparing the average of different diffusion coefficients, it was found that the diffusion rate of Ti in the Zr–Ti–Nb alloys was generally faster than that of Nb and that the diffusion rate increased as the temperature increased. The main diffusion coefficients D˜TiTiZr and D˜NbNbZr decreased as the concentration of Ti or Nb increased, and the rate of decrease was affected by the x (Ti)/x (Nb) ratio in the Zr alloys. A high x (Ti)/x (Nb) ratio could slow down the reduction trend of the main diffusion coefficients. The impurity diffusion coefficients of Ti in Zr–Nb binary alloys decreased as the concentration of Nb increased, while the impurity diffusivities of Nb in Zr–Ti alloys exhibited an opposite trend.