Analysis of grain growth process in melt spun Fe-B alloys under the initial saturated grain boundary segregation condition

A grain growth process in the melt spun low-solid-solubility Fe-B alloys was analyzed under the initial saturated grain boundary (GB) segregation condition. Applying melt spinning technique, single-phase supersaturated nanograins were prepared. Grain growth behavior of the single-phase supersaturated nanograins was investigated by performing isothermal annealing at 700 °C. Combined with the effect of GB segregation on the initial GB excess amount, the thermo-kinetic model [Chen et al., Acta Mater. 57 (2009) 1466] was extended to describe the initial GB segregation condition of nanoscale Fe-B alloys. In comparison of pure kinetic model, pure thermodynamic model and the extended thermo-kinetic model, an initial saturated GB segregation condition was determined. The controlled-mechanism of grain growth under initial saturated GB segregation condition was proposed using two characteristic annealing times (t₁ and t₂), which included a mainly kinetic-controlled process (t ≤ t₁), a transition from kinetic-mechanism to thermodynamic-mechanism (t₁ < t < t₂) and pure thermodynamic-controlled process (t ≥ t₂).