Improving the mechanical and magnetic properties of equiatomic FeCo-2V alloy through mild magnetic field annealing

Abstract

Annealing treatment in a mild magnetic field has been investigated on the mechanical and magnetic properties of the FeCo-2V alloy. Samples were annealed at 750 °C and 880 °C for various holding times (3, 6, or 9 hours) with an external magnetic field (0, 3300 or 5500 A/m). The mechanical strength, magnetic properties, and grain size of annealed samples were measured. The results show that the magnetic-field-annealing (MFA) treatment retards the grain growth, and the small grains result in an increase in the mechanical strength. Moreover, there is a significant improvement in the magnetic properties. The unusual correlation between the small grains and improved magnetic properties is explained through grain shape anisotropy. Moreover, MFA is found to be more effective in improving the magnetic properties of FeCo-2V alloy than extending the holding time. The 880-6-5500 samples exhibit a high maximum permeability of about 35000, the lowest core loss and coercivity with 34.4 W/kg and 85.9 A/m, respectively at 2.0 T/400 Hz. The finding reveals a practical route to improve the mechanical and magnetic performance of electric machines by annealing under a weak magnetic field.