Structure and Soft Magnetic Properties of Nanocrystalline Fe73.5Nb2Ta1Si13.5B9Cu1 Alloy Ribbons

The crystal structure and soft magnetic properties of thermomagnetic annealed Fe₇₃.₅Nb₂Ta₁Si₁₃.₅B₉Cu₁ alloy ribbons prepared by rapid cooling were investigated. X-ray diffraction results showed that the as-cast alloy strips had a completely amorphous structure while the annealed samples formed α-Fe(Si) nanocrystals with sizes ranging from 7 to 17 nm. Differential scanning calorimetry analysis of the as-cast samples indicated an exothermic crystallization peak at 515°C of the first crystallization stage corresponding to the formation of α-Fe(Si) crystalline phase. The as-cast ribbon samples were annealed at 500 °C for 30, 40, 50 min and in a saturation magnetic field of 10 Oe. The crystallinity of the alloy ribbons thermomagnetic annealed at 500°C for 30 min was determined by DSC analysis to be 45%. The optimum annealing time to achieve the best magnetic properties was 40 min and the thermomagnetic annealed alloy ribbons exhibited excellent soft magnetic properties, with a saturation susceptibility Bs = 1.45 T, coercivity Hc = 0.015 Oe and maximum permeability μmax = 551,500.