Structural studies of secondary crystallization products of the Fe23B6-type in a nanocrystalline FeCoB-based alloy

A stable Fe23B6-type phase formed in a nanocomposite soft magnetic alloy Fe40Co40Nb4B13Ge2Cu1 after thermal treatment was investigated. The primary crystallization temperature and second crystallization temperature for this alloy were determined to be 405 and 740 degrees C, respectively. After annealing the sample at 820 degrees C for 1 h, a Fe23B6-type phase (FeCoNb)(23)B-6 was observed. The structural information was investigated by x-ray diffraction, transmission electron microscopy, and three-dimensional atom probe. The Fe23B6-type phase contains about 33 +/- 5 at. % Fe, 38 +/- 5 at. % Co, 7 +/- 1 at. % Nb, and 20 +/- 3 at. % B. The Nb atoms tend to occupy the 8c sites and Co/Fe atoms occupy the 4a, 32f, and 48h sites of the Fm3m space group for this structure. (c) 2007 American Institute of Physics.