Effects of Si/B ratio on the isothermal crystallization behavior of FeNiSiBCuNb amorphous alloys

摘要

In the present work, (Fe40Ni40SixByCu1)(0.97)Nb-0.03 (Si/B = 1:1, 1:2, and 1:3) alloys were prepared by the as-melt spun method. The effect of different Si/B ratios on the isothermal crystallization behavior of FeNiSiBCuNb glass alloys were investigated. The activation energies of the Si/B = 1:1, 1:2, and 1:3 alloys for nucleation and grain growth were calculated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) model as 123.6 kJ/mol and 207.3 kJ/mol, 151.0 kJ/mol and 251.3 kJ/mol, and 88.6 kJ/mol and 170.0 kJ/mol respectively; hence, crystal nuclei needed to cross a higher energy barrier in the growth process. The variation of local Avrami exponent n(alpha) with crystallization fraction a demonstrates that the crystallization mechanism was divided into three stages: i: initial crystallization stage with n>2, indicating that alpha-Fe(Si) phase or gamma-(Fe, Ni)Si phase with a high nucleation rate stage, ii: middle crystallization stage with n approximate to 2, indicating that FeNiB phase with a stable nucleation stage, and iii: the end of crystallization stage with n<2, indicating that gamma-(Fe, Ni)Si and FeNiB phases with a growth stage; The crystallization process was transformed from diffusion-controlled one-dimensional growth to diffusion-controlled three-dimensional growth.