Structural investigations of Fe–Ga alloys: Phase relations and magnetostrictive behavior

The underlying relation between the magnetostriction (3/2) λ100 and Ga concentration for Fe–Ga alloys is an open question. This work presents a systematic structural study of the structure-property dependence of Fe–Ga alloys by transmission electron microscopy and X-ray diffraction. Results show that in the regions where monotonic increases in (3/2) λ100 are exhibited, single-phase A2 or D03 is found for the slow-cooled alloys. For the alloys in the range 18–21 at.% Ga, quenching extends the single-phase A2 to higher Ga concentrations, thereby continuing to enhance magnetostriction. The sudden decrease in (3/2) λ100 near Fe–19 at.% Ga as well as Fe–29 at.% Ga was associated with the formation of phase mixtures. For quenched alloys between 25 and 29 at.% Ga, a phase mixture of (A2 + B2 + D03) was found, but the presence of this phase mixture does not seem to have a large effect on magnetostriction.