Influence of composition in the crystallization process of Fe75−xNb10B15+x metallic glasses

The devitrification process of Fe_75−xNb₁₀B_15+x (x = 0, 5, 10) metallic glasses produced by melt-spinning has been analyzed by calorimetric, microstructural and magnetic measurements. The experimental results show large differences in the behavior of these alloys as a function of composition. The alloy x = 0 undergoes a primary crystallization process separated in two stages while only one is observed for alloys with x = 5 and x = 10. This difference, observed by DSC, is correlated with a microstructural change in the phases that precipitate. For alloys x = 5 and 10, Fe₂₃B₆ and bcc-Fe are identified after the first calorimetric peak. In the sample x = 0, bcc-Fe and an unidentified phase precipitate in the first peak but massive crystallization of bcc-Fe is observed after the second stage. Finally the thermal dependence of magnetization has been measured and the Curie temperatures for the metallic glasses are determined. The change of these quantities with heat treatment and composition is discussed.