bstract In this research, microstructural evolutions and grain boundary character distribution during high energy beam welding processes of ultra-thin FeCo-V foils were studied. Also, mechanical and magnetic properties evolutions during high energy beam welding were studied using tensile test and vibrating sample magnetometry (VSM), respectively. It was found that the fractions of low angle boundaries increase in the fusion zones of both electron and laser beam welded foils. The results showed that the fractions of low ? CSL boundaries (especially twin boundary, ?3) in the fusion zones of the welded foils are higher than those of base metal. Since the strain rates produced during high energy beam welding is very high (duo to the extremely high cooling rate), grain deformation by slip mechanism is limited, and therefore deformation by grain twinning is dominant. VSM analysis showed that the welded foils experience a significant decrease in their magnetic properties; i. e. remanence, coercive force and energy product. The results demonstrated that all of the welded specimens fractured in the fusion zones. Keywords: FeCo-V alloys; Ultra-thin magnetic foils; micro-welding; Mechanical properties; Magnetic properties
