Crystallization kinetics in amorphous rare-earth–transition-metal alloys

The kinetics of crystallization have been examined in amorphous melt-spun R₅₀{T}₅₀$ alloys with R=Nd,Tb and T=Fe,Co using the Kissinger method and the Johnson-Mehl-Avrami equation. The crystallization temperatures ${T}crfound were in the range of 192--493 ^∘C with the Fe- and Nd-containing alloys having the higher{T}cr$. The calculated activation energies were found to scale with the crystallization temperatures and were in the range of 1.61--2.48 eV. The Avrami exponent n obtained was in the range of 2.1--3.7 with the lower value occurring in Tb₅₀{Fe}₅₀$. In ${Nd}₅₀Fe₅₀, n=3, indicating a uniform three-dimensional growth.