Influence of microstructure and texture evolution on magnetic properties attained by annealing of a cold-rolled Fe-Co-10V semi-hard magnetic alloy

Abstract

Typically, in processing of Fe-Co-V type magnetic alloys, hot rolled sheets are being severely cold rolled and then annealed at a specific temperature for an appropriate soaking time. In this work, in order to achieve the optimal magnetic properties, effect of various annealing cycles after 86% cold rolling on a 40Fe-50Co-10V (wt%) alloy were examined and the correlation between magnetic properties and microstructure and texture evolution was investigated. In order to supplement extensive microstructure evolution data available from previous publications, texture analysis was carried out using X-ray and electron backscatter diffraction methods and magnetic properties were determined via a vibrating sample magnetometer. It was observed that by increasing the annealing temperature the saturation magnetization decreased due to the formation of paramagnetic (Co,Fe)3V precipitates and austenite, while the coercivity increased in a reverse manner. The impact of austenite on decreasing the saturation magnetization was more pronounced than that of precipitates. Phase boundaries were more effective than grain boundaries in promoting the coercivity. However, nano-size (Co,Fe)3V precipitates inside the ferromagnetic matrix were also important in enhancing the coercivity. Besides formation of the precipitates, variations of the intensity of 〈111〉 direction as hard magnetic direction and intensity of {111}〈112〉 texture component, led to the alteration of magnetic remanence attained at 500–750 °C. Based on application of these alloys as semi hard and hard magnets, the optimal magnetic properties are achieved at a temperature range of 550–650 °C.