Crystallization kinetics and phase transition under high-pressure of amorphous Sm 8Fe 85Si 2C 5 alloy

Abstract

The crystallization kinetics and phase transition under high pressure of amorphous Sm 8Fe 85Si 2C 5 have been investigated. The activation energy of crystallization of both α-Fe and Sm 2(Fe,Si) 17C x 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/Sm 2(Fe,Si) 17C x 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 Sm 2(Fe,Si) 17C x 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 Sm 2(Fe,Si) 17C x increases with pressure. As pressure increases to 6 GPa, a change in crystallization sequence between the α-Fe phase and the Sm 2(Fe,Si) 17C x phase is observed.