Structural evolution with Nb content in melt-spun Fe80−xSi20Nbx ribbons

The structural evolution with increasing Nb content in Fe80−xSi20Nbx alloys (0 < x ≤ 12) was investigated by means of high-resolution X-ray diffraction. A metastable NbFe2−xSix hexagonal phase was found together with cubic bcc Fe100−ySiy solid solution and the amorphous matrix. The grain size of the bcc Fe100−ySiy phase and the strain were determined and their dependencies on the Nb content and heat treatment of the samples were investigated. The strain increases and the grain size decreases with an increasing of Nb content reaching a size down to 37 nm. Upon heat treatment of the samples, the hexagonal phase decomposes in two hexagonal phases with similar compositions.