Rapidly quenched (RQ) Fe-B-P alloys with addition of Co and Cu exhibit excellent soft magnetic and mechanical properties. A system of the type (Fe85-zCozB15)(100-x-y)PxCuy with x = 3, 4, 5; y = 0, 1 and z = 0, 21 at.% has been prepared by planar flow casting in form of thin ribbons. Selected properties in as-cast state and after controlled annealing targeted to produce fine-grain structure were determined. The effect of the substitution of Fe for Co and the additions of P and Cu on structure in nanocrystalline state was investigated. These systems were investigated by thermogravimetry (TGA) and by differential scanning calorimetric (DSC) measurements. The structure was investigated by XRD and TEM (HREM). (C) 2012 Elsevier B. V. All rights reserved.