Magnetostriction of heavily deformed Fe-Co binary alloys prepared by forging and cold rolling

Magnetostriction of Fe_1-xCo_x (x = 50-90 at%) alloys prepared by forging and subsequent cold-rolling was studied as functions of alloy compositions and thermomechanical treatments. Magnetostriction of the as-forged Fe₂₅Co₇₅ alloy was 108 ppm and that of the as-cold rolled Fe₂₅Co₇₅ alloy measured parallel to the rolling direction (RD) was 128 ppm. The cold-rolled Fe₂₅Co₇₅ alloy possessed a nearly {1 0 0}<0 1 1> texture, leading to the maximum magnetostriction of 140 ppm when measured at an angle of 45° to RD. Moreover, the fully annealed Fe₂₅Co₇₅ and Fe₂₀Co₈₀ alloys were gradually cold rolled and magnetostriction were measured. Results showed that the magnetostriction of those cold-rolled alloys drastically increased with increasing reduction rate. According to the XRD and TEM observations, intensity of the fcc peak gradually decreased with increasing reduction rate and that the alloys became to be in a bcc single state at a reduction rate higher than 90%, leading to a drastic increase in magnetostriction.