Role of structural ordering on magnetostrictive property of Fe-Ga alloys

Fe–x at% Ga (x = 17, 20, 23 and 25) were prepared by vacuum arc melting and subsequently exposed to different thermal treatments. The microstructure and magnetostrictive properties of the alloys exposed to various thermal histories have been investigated in detail. Detailed microstructural investigation indicates that at lower Ga concentration (17 and 20 at%), the ordering of A2 phase into DO3 occurs through diffusion assisted nucleation and growth transformation. On the contrary, the alloys richer in Ga exhibits ordering of A2 to DO3 through successive continuous ordering processes of A2→B2 and B2→DO3. The continuous ordering transformations being spontaneous process, the ordering could not be suppressed even by water quenching. The ordering is found to have profound influence on magnetostriction of the Fe-Ga alloy as higher magnetostriction was observed in either completely disordered A2 or completely ordered DO3. The magnetostriction is found to decrease in partially ordered material where DO3 phase co-exists with A2.