Secondary crystallization in (Fe65Co35)79.5+xB13Nb4−xSi2Cu1.5 and (Fe65Co35)83B10Nb4Si2Cu1 nanocomposite alloys

Abstract

Here, secondary crystallization kinetics of high induction, low loss HTX002-type nanocomposite alloys with the compositions (Fe65Co35)79.5+xB13Nb4−xSi2Cu1.5 (x = 0-4) and (Fe65Co35)83B10Nb4Si2Cu1 are reported. The magnetization of the alloys was measured through the thermal cycle of 50 °C-700 °C-300 °C-800 °C-300 °C-900 °C-200 °C by vibrating sample magnetometry. In (Fe65Co35)79.5+xB13Nb4−xSi2Cu1.5 alloys, the stability of the (Fe,Co,Nb)23B6 (23-6) phase is increased with increasing Nb content. In the x = 4 alloy, (Fe,Nb)2B is the only secondary crystalline phase to form, demonstrating that Nb is necessary for the 23-6 phase to form. The (Fe65Co35)83B10Nb4Si2Cu1 alloy forms the 23-6 phase more readily than the x = 0 alloy, likely due to the lower B content. The kinetics of secondary crystallization are important to assess long-term ageing effects on the metastable microstructure at elevated temperatures.