Magnetostriction and structure characteristics of Co70Fe30 alloy prepared by directional solidification

Highlights: • The magnetostriction as high as 180 ppm is achieved in Co₇₀Fe₃₀ alloy. • Nanoscale fct phase particles can increase the magnetostriction of Co₇₀Fe₃₀ alloy. • The precipitation temperature of fct phase is 780 °C ̃ 860 °C in Co₇₀Fe₃₀ alloy. In this work, 1 0 0 textured Co₇₀Fe₃₀ alloy was successfully prepared by directional solidification technique. The effect of heat treatment on magnetostriction and microstructure of Co₇₀Fe₃₀ alloy has been investigated. The Co₇₀Fe₃₀ alloy was annealed in argon atmosphere at 700 °C–900 °C for 9 days and then cooled to room temperature by slow cooling or quenching. The magnetostriction as large as 180 ppm has been achieved for the quenched samples when the annealing temperature is ranging from 820 °C to 860 °C. Structural analyses indicate that the large magnetostriction originates from precipitation of a nanoscale face-centered tetragonal (fct) phase embedded in a body-centered cubic (bcc) phase matrix.