High temperature aging behavior of high strength 49%Co-1.9%V-0.3%Nb-Fe soft magnetic alloy

The magnetic and mechanical properties of 19%Co-1.9%V-0.3%Nb-Fe high strength (/spl sigma//sub y/=90 ksi) soft magnetic alloy were studied after aging at 450/spl deg/C for up to 800 h. The magnetic induction B (H/sub m/=10 and 25 Oe respectively) decreases rapidly in the first 100 h and approaches a lower limit at about 300 h. The coercive field remains constant during aging. Tensile specimens aged for 200 h at 450/spl deg/C did not show any changes in the room temperature yield stress and elongation. Transmission electron microscopy identified two precipitate phases: NbC and a Laves phase (hcp. a=4.7 /spl Aring/, c=7.72 /spl Aring/). The Laves phase appears in grain boundaries and triple-points and inhibits the grain growth therefore enhancing the mechanical properties.