Enhancement of mechanical properties in FeCo magnetostrictive alloys with an addition of NiMn

Large magnetostriction has been discovered in the FeCo binary alloys at the composition of Fe₃₀Co₇₀. In this paper, a series of (Fe₃₀Co₇₀)_100-x(NiMn)_x cast alloys is developed. The mechanical properties and magnetostriction of these alloys are intimately related to the crystal structure and phase constituent. The (Fe₃₀Co₇₀)_100-x(NiMn)_x magnetostrictive alloys keep in the body-centered-cubic (bcc) phase region with the addition of NiMn to 5%, where the strength and ductility are intensively improved simultaneously. The enhancement of the mechanical behaviors is attributed to the generation of fine laminate structure after doping. The tensile strength and magnetostriction drop with increasing NiMn content when the face-centered-cubic (fcc) phase appears. In (Fe₃₀Co₇₀)₉₅(NiMn)₅ polycrystalline alloy, a magnetostriction of 114× 10⁻⁶ coupled with a yield strength of more than 1200 MPa and a tensile elongation of 5% is achieved.