Influence of thermal treatment on structure development and mechanical properties of amorphous Fe73.5Cu1Nb3Si15.5B7 ribbon

Ribbon-shaped amorphous samples with the stoichiometric composition Fe73.5Cu1Nb3Si15.5B7 prepared by the melt spinning process were annealed at temperatures ranging from 693 K to 1123 K for 1 h under vacuum. In the early annealing stage, the alloy undergoes a specific nucleation process where Cu clusters precipitate from an amorphous matrix. Further heating initiates the partial crystallization of alloy forming the α-Fe–Si nanocrystallites. Subsequent Vickers hardness tests showed high values depending on the annealing temperature. It was found that the hardening process includes two stages. This behavior correlates well with results of density dislocation calculations. A crystallite size of 10 nm for the α-Fe–Si particles correlated very well with a maximum hardness of the material.

Research highlights▶ Amorphous ribbon with the composition Fe73.5Cu1Nb3Si15.5B7 prepared by the melt spinning process were annealed at temperatures ranging from 693 K to 1123 K for 1 h under vacuum. ▶ In the early annealing stage, the amorphous alloy undergoes a specific nucleation process where Cu clusters precipitate from the amorphous matrix. ▶ Further heating initiates partial crystallization through formation of α-Fe–Si nanocrystallites in intimate contact with Cu clusters. ▶ It was found that the hardening process consists of two stages: for T < 873 K the hardening behaviour is controlled by a shear deformation mechanism in the amorphous matrix; for T > 873 K, the hardening behaviour is dominated by the dislocations movement, which in conjunction with appearance of the other crystalline phases upon annealing leads to the decrease of hardness.