Nanostructure refinement and phase formation of flash annealed FeNi-based soft magnetic alloys

The resulting nanocomposite microstructures of FeNi nanocrystallites under different heating and cooling rates (5 ?/min vs 400-500 ?/s) is investigated. Conventional furnace annealing under low heating rates and slow cooling resulted in both BCC alpha-FeNi and FCC gamma-FeNi nanocrystallites with an average grain size on the order of 25-27 nm whereas high heating rates achieved via flash annealing techniques have enabled a dramatically refined microstructure consisting of 5-7 nm grains with FCC gamma-FeNi phase and found to be the dominant phase following primary crystallization. Grain size refinement and phase identity optimization yielded low values of coercivities-17 A/m and high permeability similar to 11 x 10(3) measured at 400 Hz/1 kA/m in flash annealed samples at 450 ? for 5 s. The magnetic behavior and the underlying mechanism of optimal soft magnetic properties are discussed in terms of the critical role of the grain size in domain wall pinning and coercivity.

Automated summary

The resulting nanocomposite microstructures of FeNi nanocrystallites were investigated under different heating and cooling rates. It was found that high heating rates achieved via flash annealing techniques can lead to a refined microstructure with smaller grain size and improved soft magnetic properties.