Aspects of phase equilibria in Fe/Co/2.5 to 3.0% V alloys

Remendur alloys, one of which is used as the base material in remanent reed sealed contacts for the communications industry, are ternary alloys containing approximately equal iron and cobalt with 2 to 4 wt % vanadium. The available equilibrium diagram for this system does not provide precise positioning of the phase boundaries in the regions of commercial interest and, consequently, does not permit accurate determination of the amounts of the phases present or their compositions. This paper reports on the precise determination of five tie lines in theα ₁+γ two-phase field in the region of interest, by metallographic and microprobe techniques. In the 900 to 950° C range, this field was found to be narrower than expected from published data. Submicron fcc (γ) particles form during annealing at 600° C by decomposition of a non-equilibrium bcc (α₂) phase into a secondary ordered bcc phase (α′₁) and stabilizedγ. Deformation, by drawing and by stamping, enhances coercivity in these alloys by promoting a more uniform, more finely divided dispersion ofγ particles. Annealed microstructures are especially sensitive to vanadium content, annealing temperature, and annealing time.