Cold-formable Cr-Co-Fe alloys for use in the telephone receiver

Six alloys based on the Cr-Co-Fe system have been developed which can be cold-drawn into cups, heat treated to form magnets with energy products in the range 1.5 to 1.8 million gauss-oersteds. Such magnets have been fabricated into ring-armature-type receivers which can be used in the telephone handset. The alloys are based on the composition 28% Cr-15% Co-Fe with additions of Zr, Al, Nb, Ti, V, and Mo. The two most promising alloys consist of 1 Al-¼ Zr and 1 Nb-¼ Ti-¼ Zr. The former alloy can be solution treated at 900°C; the latter requires 1050°C.