Electron beam assisted joining of nanograin-sized Fe–Co–V magnetic foils: Study and optimization of magnetic properties of weld joints

Abstract

Fe–Co–V alloys are of interest due to their excellent magnetic properties. These alloys are frequently used in the active parts of rotors of synchronous hysteresis motors. Welding of these alloys is however a great challenge because of various phase transitions occurring during solidification. These phase transitions change the microstructural, physical and mechanical properties of Fe–Co–V alloys. In this research work, the effect of electron beam welding on the magnetic properties of nanograin-sized Fe–Co-7.15wt%V foils was studied. Microstructural observation and texture analysis were carried out in order to clarify the changes of magnetic properties in the welded area. It was found that the magnetic properties of the welded area experience significant decrease due to the formation of large grains that have unfavorable orientation in the fusion zone. Also, a statistical analysis of the electron beam welding of this alloy was done using response surface methodology. The analysis considered the effect of beam current (0.7–1.7 mA), beam voltage (40–50 kV), welding speed (150–500 mm/min) and focused position (−20 to 0 mm) on the energy product ((BH)max) of welded samples. The experimental design was based on four-factor, five-level central composite rotatable design using linear and quadratic polynomial equations for proposing the mathematical model.