| As a new intelligent material,Fe-Ga alloy can be used in actuator,sensor,transducer and other high-tech fields because of its low driving magnetic field,high saturation magnetostrictive coefficient and good mechanical properties.In this study,single crystal Fe72Ga28 alloy was prepared by directional solidification method.Different composite phase structures were prepared by adjusting heat treatment parameters.The formation and transformation of phase structure in single crystal and heat treatment process of Fe72Ga28 allo y were characterized and analyzed.The effects of phase transformation and phase structure on magnetic properties and magnetostrictive properties of the material were studied.The conclusions are as follows:(1)The axial temperature gradient of solidification process is effectively improved by adding lateral heat preservation device to restrain radial heat dissipation,and then the single crystal of Fe72Ga28 alloy is prepared by adjusting the growth rate.With the growth rate decreasing from 2.0 mm/min to 0.3 mm/min,the grain size increases gradually;When the growth rate is 0.3 mm/min,the grain size of the sample reaches 4.0 mm,and the grains penetrate the sample along the axial direction.(2)The phase structure transformation of Fe72Ga28single crystal after holding at 1100?for 1 hour,holding at 450?,500?,600?,650?and 700?for 3 hours and water quenching was studied.It was found that L12 phase was precipitated in all samples,and the volume fraction of L12 phase in the sample holding at 450?and water quenching was 34.1%.(3)The phase structure transformation of Fe72Ga28 single crystal after holding at 1100?for 1 hour,450?for different time and water quenching was studied.It was found that the volume fraction of L12 phase increased with the increase of holding time,and the volume fraction reached 41.2%after holding at450?for 24 hours.(4)The phase structure transformation of Fe72Ga28single crystal after holding at 1100?for 1 hour,650?for different time and water quenching was studied.It was found that with the increase of holding time,the phase structure of room temperature microstructure changed from bcc structure phase to bcc structure phase+L12phase,and then to bcc Structure phase.(5)The effects of different phase structure on the magnetostrictive properties and magnetic properties of Fe72Ga28 single crystal were studied.It was found that with the increase of L12 phase volume fraction,the magnetostrictive properties decreased gradually,while the saturation magnetization and coercivity increased gradually.When the volume fraction of L12 phase is 41.2%,the magnetostrictive coefficient is only 17.9×10-6.The saturation magnetization is140.6emu/g,while the magnetostrictive coefficient of bcc structure is 102.9×10-6.The saturation magnetization is 131.0 emu/g... |
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