Nitriding thermochemical treatment and niobium dual effect on nanocrystallization of FeSiBCu ribbons

In recent years, nanocrystalline magnetic materials have been widely investigated in order to manufacture a material with high saturation magnetic flux density, and good soft magnetic properties compatible with thermal stability. These materials have been achieved by the granular structure crystallized from an amorphous phase as is the case for Fe73·5Cu1Nb3Si13·5B9 melt spun ribbon. This material exhibits excellent soft magnetic properties due to the formation of bcc Fe(Si) nanocrystallites immersed in a remaining amorphous phase. Such a material has a magnetostriction close to zero. The factors contributing to such nanophased structures are the additive elements to the basic FeSiB system, and the method of treatment. Copper addition is known to increase the nucleation centers in crystals while niobium is known to hinder their growth process. Conventional thermal treatment (CTT) is commonly used as annealing method. In this study, starting from the FeSiBCu system, the authors have added Nb. For the annealing, they have used a nitriding thermochemical treatment (NTT). The authors show the nitriding treatment effect on the structural behavior of FeSiBCu(±Nb) ribbons and they propose a nitriding mechanism