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In this work, the effects of annealing temperatures and time on the microstructure and soft magnetic properties of (Fe 0.83 B 0.11 Si 0.02 P 0.03 C 0.01) 99.5 Cu 0.5 nanocrystalline alloy were investigated using a new rapid annealing process. The results show that at each annealing temperature, there exists an annealing time for optimum soft magnetic properties. The annealing temperature and time were further optimized, and excellent properties with high saturation magnetic induction B s of 1.79 T and low coercivity H c of 2.7 A/m were obtained by annealing at 431 °C for 150 s. A microstructure consisting of uniform and fine α-Fe(Si) grains with high number density and high crystallization volume fraction was found to be the key to ensure high B s and low H c. However, with increasing annealing time, it was found that α-Fe(Si) grains existed aggregation phenomenon (in the form of high-angle grain boundaries), with the simultaneous precipitation of Fe-B compound precipitated in the residual amorphous matrix. This not only causes the uneven distribution of nanocrystals, but also destroys the competitive effect between nanocrystals and the stability of the structure, thus deteriorating the soft magnetic properties. [ABSTRACT FROM AUTHOR]

• The trajectories for optimized B s and H c determined by both annealing temperature and time were established. • A relatively larger B s up to 1.74 T and lower H c of 4.9 A/m were found for the present alloy compared to the nanocrystalline alloys with similar Fe content. • It is found that the precipitated α -Fe (Si) grain number density is the main factor to determine the B s A (Fe 0.83 B 0.11 Si 0.02 P 0.03 C 0.01) 99.5 Cu 0.5 glass former was formulated based on Fe 83 B 11 Si 2 P 3 C 1 alloy and a new rapid annealing method was employed to investigate both the temperature and time effect on the improvement of soft magnetic properties of the amorphous alloy ribbon. The results show that the interval between the first and second crystallization temperature is enlarged by Cu addition. There exists an optimal annealing time corresponding to the optimal B s and H c for the ribbon annealed at each temperature. The maximum B s up to 1.74 T and the minimum H c of 4.9 A/m were obtained for the ribbon annealed at 426 °C for 150 s. The grain number density of precipitated α -Fe(Si) is the main factor in determining the B s. Compared to other nanocrystalline alloys with similar Fe content, the present alloy ribbon annealed by the new method shows a higher B s and a lowest H c , which makes it a promising soft magnetic material used in the field of electrical and electronic industries. [ABSTRACT FROM AUTHOR]