Influence of thermal treatment on structure and microhardness of Fe75Ni2Si8B13C2 amorphous alloy

Correlation between hardness of amorphous Fe75Ni2Si8B13C2 alloy and thermally induced structural transformations has been investigated by measuring microhardness in a series of samples heated at different temperatures from 25 to 1000 °C. The alloy has a relatively high hardness in the amorphous state, due to its chemical composition involving silicon, boron and carbon. As the alloy begins to crystallize, microhardness increased and reached a plateau in 500–650 °C temperature region, due to formation composite structure involving the small nanocrystals of α-Fe(Si) and Fe2B phases dispersed in the amorphous matrix. After treatment at higher temperatures, the nanocomposite structure is replaced by a more granulated structure, leading to decline in microhardness.