Study On Secondary Recrystallization And Microstructure Of Fe-Ga Alloy Sheet

As a giant magnetostrictive material,Fe-Ga alloy(Galfenol)has attracted more and more attention due to its high tensile strength,high magnetic permeability,low saturated magnetic field and good temperature property.At present,the rolling and annealing methods are mainly used,and the secondary recrystallization process is used to strengthen ? texture and increase the magnetostriction coefficient.Internationally,NbC is mainly precipitated or added as a main inhibitor,and the surface energy effect under the atmosphere of H2S or S element is used to induce secondary recrystallization of Goss grains,thereby improving the magnetostrictive properties of the sheet.There is still a gap between the improvement of the orientation of Goss grains and the magnetostrictive performance in secondary recrystallized by controling the orientation of Goss grains in silicon steel in the current study,which is attributed to the match of inhibitor system and the grain boundary mobility of Fe-Ga alloy.In this study,Fe-Ga alloy sheet with secondarily recrystallized Goss grain was prepared by constructing a composite inhibitor system composed by MnS and Cu2S.The magnetostriction coefficient was optimized by regulating the existence of the RE element in the secondary recrystallization sheet.Combining macrostructure and microstructure,precipitated phase and texture characterization methods,reveal the evolution of microstructure,texture and inhibitor characteristics during rolling and annealing,and clarify the formation and development mechanism of secondary recrystallization texture.The main conclusions are as follows:(1)Based on the construction of the compound inhibitor system(MnS+Cu2S),the nano-sized precipitates are obtained through the composition design,rolling and annealing process control,and the primary grain growth is effectively pinned in the initial recrystallization and slow heating stages.In the process of heating,the coarsening of the secondary nucleus is induced and grown.During the heating process,the coarsening induces the formation and growth of the secondary nucleus,and finally the Fe-Ga alloy sheet with perfect Goss texture and excellent magnetostrictive properties is obtained.(2)The Mn and Cu contents are the key to determine the degree of secondary recrystallization and magnetostrictive properties.Under low Cu+Mn composition,secondary recrystallization is not complete.With the increase of Mn and Cu,the secondary recrystallization temperature is increased,and the degree of secondary recrystallization is improved.The secondary recrystallized Goss grains of near centimeter size are obtained at higher Mn and Cu compositions,and the magnetostriction coefficient is up to 260 ppm.(3)The addition of the RE element affects the secondary recrystallization texture formation and magnetostriction coefficient of the Fe-Ga alloy sheet.The addition of the RE element causes the start and completion temperatures of secondary recrystallization to decrease by 50?,effectively increasing the magnetostriction coefficient.By quenching,the solid solution amount of RE element is increased,and lattice distortion is caused,and nanometer-size heterogeneity is formed,resulting in a remarkable increase in magnetocrystalline anisotropy,resulting in a significant increase in magnetostriction,and finally reaching 323 ppm.(4)The magnetostriction coefficient of Fe-Ga alloy is determined by the orientation deviation angle of Goss grains,which originates from the transformation law of 1800 and 90°magnetic domains during magnetization.Magnetostriction mainly comes from the structure of the lancet domain in the presence of orientation deviation,and the rotation of the domain in the<001>direction to the<010>and<100>directions during the vertical magnetization process.In this study,Fe-Ga alloy sheet with high magnetostrictive properties of secondary recrystallized Goss texture was prepared by inhibitor system selection,rolling and annealing process regulation and RE element solid solution.In the future,it is necessary to improve the magnetostrictive properties of the Fe-Ga alloy sheet by optimizing the rolling and annealing process parameters.