The paper presents a structural relaxation process of Fe78Si9B13metallic glasses and structure and properties changes in a temperature range up to 300°C after annealing from 2 to 16 hours.

The relaxation and crystallization of Fe78Si9B13metallic glasses were examined by mechanical test, relaxation test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods.

The influence of thermal activation on the structural relaxation process of Fe78Si9B13metallic glasses was determined after annealing from temperature of 100 to 300°C. The beginning of the structural relaxation was revealed after annealing at 100 and 150°C, especially after long annealing times of 8 and 16 hours. The structural relaxation process was confirmed by examination of dimensional changes of samples associated with partial reduction of free volume and the ordering of topological and chemical structure of metallic glass. Significant changes in the structure and properties of the alloy was observed after annealing at 300°C. The reduction of tensile strength and high fragility of samples was also determined. This decrease is associated with extending of the structural relaxation and beginning of crystallization process by formation of small crystallites of α-Fe phase in amorphous matrix.

The structural relaxation process and beginning of crystallization on changes of strength, ductility, fracture morphology, structure, process of stress relaxation and geometry of studied alloy were also achieved in function of temperature and time of annealing.

The course of relaxation processes can be used for analysis of thermal stability of metallic glasses.

The paper presents a significant influence of low-temperature thermal activation, which was conducted up to 16 hours, on the structural relaxation and changes of selected mechanical properties.