Microstructure and maganetostrictive properties of Fe₈₅Ga₁₅ ribbons

Background: Fe-Ga alloy is a new magnetostrictive material of lower price and better extensibility in comparison with conventional Tb-Dy-Fe alloys. Many researches revealed that the microstructure and magnetostriction are influenced by preparing method and heat treatment. Purpose: In order to study the influence of microstructure on magnetostrctive properties of Fe-Ga alloy, the phase structures, local structure and magnetostrictive properties of Fe₈₅Ga₁₅ ribbons prepared by different wheel speed was studied. Methods: We utilized high resolution x-ray diffraction (HRXRD) to characterize the phase structure and used Extend X-ray absorption fine structure (EXAFS) to study the local structure of the ribbons in Synchrotron Radiation Facility. Results: X-ray diffraction showed that only disordered BCC phase was observed in as-cast Fe₈₅Ga₁₅ alloy. Modified-DO₃ phase were detected in all of the melt spun samples. Both the HRXRD and EXAFS results indicated that Ga atoms were located as second-nearest neighbour along [100] orientation. A little DO₃ phase was found in ribbons annealed at 1000°C under Ar atmosphere. Conclusions: Higher wheel speed will generate more modified-DO₃ phase which will enhance the magnetostriction. DO₃ phase in the annealing sample will deteriorate the magnetostrictive properties of Fe-Ga ribbons.