Nanocrystallization behavior of Fe₄₀Ni₃₈B ₁₈Mo₄ soft magnetic alloy

The Herzer model suggests that superior magnetic properties can be observed in magnetic alloys provided a suitable microstructure consisting of soft magnetic nanometre size precipitates separated by nanometre size distances is obtained. In order to explore new magnetic alloy compositions which can satisfy the Herzer model, we studied selected alloys in which we wished to obtain suitable microstructures, one such alloy has the composition Fe ₄₀Ni₃₈B₁₈Mo₄. This alloy is amorphous as received, the heat treatment schedule required to obtain nanoprecipitates was designed based on DSC, resistivity and x-ray results. Heat treatment at temperatures between 420°C and 500°C and different heat times was carried out on the amorphous ribbon. Transmission Electron Microscopy (TEM) results of the early stage of crystallization behavior showed that soft magnetic precipitates of nano-size were indeed observed within the amorphous matrix. The crystal structure, composition analysis and thermal stability of the precipitates were studied by XRD, EDS and TEM. These results will be presented and the implication of these results to the production of new soft magnetic alloys will be emphasized.