Design of high ductility FeGa magnetostrictive alloys: Tb doping and directional solidification

Decent magnetostriction of ~ 255 ppm and giant tensile strain of ~ 6.6% is obtained through trace Tb addition and directional solidification method in (Fe_0.83Ga_0.17)_{100 − x}Tb_x (x = 0–0.5) alloys. The particle-shaped Tb-rich precipitates are formed and dispersively distributed in the matrix along the (sub-) grain boundaries; preferred 〈100〉 orientation is achieved in the alloys by appropriate directional solidification process, which makes contribution to improve the magnetostriction. The formation of Tb-rich precipitates induces the transition of the fracture mechanism from brittleness to ductility. The maximal room-temperature tensile strain is obtained in x = 0.05 specimen, which is superior to existing literatures about the mechanical properties of Fe-Ga based alloys. The regular columnar grain morphologies and certain distribution pattern of granular precipitates are considered to be responsible for the excellent ductility in Fe-Ga-Tb alloys. This work may provide a new thinking to design high ductility Fe-Ga magnetostrictive alloys and significantly broaden the application of these materials in industry field.