Correlation Between Soft Magnetic Properties and Microstructure According to Heat Treatment in FeCo-2V Electrical Steel

Abstract

Fe-Co alloy has the highest saturation magnetic flux density among soft magnetic materials, and Fe50Co50 has the maximum permeability of Fe-Co alloys. However, Fe-Co alloy is difficult to use in applications due to its brittleness. Various attempts have been made to improve its mechanical properties for applications, but its magnetic properties have not been retained. This research focuses on improving the magnetic properties of Fe-Co electrical steels at various heat treatment temperatures with the addition of 2 at.% vanadium. To reveal the ordered body-centered cubic phase, which has good soft magnetic properties, the thermal properties of the steels were investigated with differential scanning calorimetry. The microstructure of the electrical steels after heat treatment was analyzed by scanning electron microscopy, and the tendencies of their magnetic properties, measured by a DC B-H loop tracer and a vibrating sample magnetometer, were explored in connection with the microstructure. The decrease in coercivity up to 800 °C was due to stress relief and grain growth, and its increase at 850 °C is believed to be due to the pinning effect of the V-rich phase in the grain boundary. The optimal heat treatment temperature was found to be 800 °C because the steel had reasonable magnetic saturation (2.28 T) and hysteresis loss (0.47 W/kg), the highest magnetic flux density at 5000 A/m, and the lowest coercivity (56.7 A/m).