Crystallization kinetics and phase transition under high-pressure of amorphous Sm8Fe85Si2C5 alloy Original Research Article

The crystallization kinetics and phase transition under high pressure of amorphous Sm8Fe85Si2C5 have been investigated. The activation energy of crystallization of both α-Fe and Sm2(Fe,Si)17Cx phases in the alloy is larger at the beginning of crystallization, and it undergoes little change in a larger range of crystallized fraction. This essentially results in the formation of an α-Fe/Sm2(Fe,Si)17Cx composite microstructure with a relatively coarse grain size. High pressure has a large effect on the phase transition of the amorphous alloy as it is annealed at 923 K. By increasing pressure from normal pressure to 6 GPa, the grain size of crystalline phases decreases from 30.6 to 6.4 nm for the α-Fe phase and from 28.7 to 5.8 nm for the Sm2(Fe,Si)17Cx phase. A small grain size of less than 10 nm is required by theoretical models for enhancing magnetic properties of the composites. The volume fraction of Sm2(Fe,Si)17Cx increases with pressure. As pressure increases to 6 GPa, a change in crystallization sequence between the α-Fe phase and the Sm2(Fe,Si)17Cx phase is observed.