Prediction of the glass forming ability in a Fe-25%B binary amorphous alloy based on phase-field method

Abstract

The critical cooling rate (Rc) calculated on the basis of the time-temperature-transformation (TTT) curve was taken as the intrinsic criteria of reflecting the glass forming ability (GFA) for the amorphous alloy. The TTT curves were plotted based on the isothermal Wheeler-Boettinger-McFadden (WBM) phase field method (PFM). By analyzing the TTT curves, the influence of different activation energy parameters E and Q for the interface mobility M and nucleation rate P respectively on Rc and GFA were investigated for Fe-25%B (mole fraction) binary amorphous alloy in present paper. The results showed that the activation energy E for the interface mobility M had litter influence on the nose temperature and time for the TTT curves. Under the different thermal activation energy Q1, Q2 and Q3 for the nucleation rate P, the temperatures and times corresponding to the nose tip were 500K, 600K, 775K and 6.2×10−4s, 4.5×10−4s, 9.5×10−4s, respectively, and the calculated values of Rc were 1.57×106K/s, 1.93×106K/s, 7.35×105K/s, respectively, which were in the range of 6.4×105 ~ 6.8×106K/s from the experimental measurements. Under the influence of thermal activation energy Q, the nose tip temperature increased, which meant Q controlled the nose tip temperature, while the higher Q would not get the perfect C shape. It was found that the values of Rc calculated based on the TTT curves by the PFM were in good agreement with the reported experimental values, which verified the feasibility of the glass prediction and the research of the intrinsic physical mechanism of the GFA by the PFM.