Influence Of Thermal Field And Magnetic Field On Amorphous Crystallization And Aging Process

With the development of material industry, the requirements for materials performance become higher and higher. The Fe-based soft magnetic materials should obtain higher magnetic softness. The traditional Al-based structural materials should exhibit better mechanical properties. The basic inner factors which could decide the final performance of materials include the composition, structure, and microstructure. It is the most effective technical means to improve the materials properties by controlling microstructure using thermal field and magnetic field when the composition of materials have been optimized. Both Fe-based soft magnetic materials and traditional Al-based structural materials could further to improve performance through adjusting the parameters of processing under thermal field and magnetic field.Aiming to the subjects mentioned above, we have comprehensively investigated the thermal properties and microstructure evolution of annealed Fe84-xSi4B12-yPyCux (x:0 and 0.7, y:0 and 4) alloys with simultaneously adding P and Cu. Crystallization behaviors and soft magnetic properties of Fex(SiB)96-xP3Cu1 (x=75,78,80,83 and 85) alloys have been studied. We optimized the compositions in FeSiBPCu alloys with Fe content higher than 85 at.%. Further researches have been proceeded in the FeSiBPCu alloys with Fe content higher than 85 at.%which were annealed at heating speed of 400K/min without magnetic field and heated at 5 K/min with and without magnetic field. A high magnetic field is involved in aging behavior of aluminum alloys. The primary conclusions are summarized as followed.The addition of 4at.%P and 0.7at.%Cu in FeSiB alloys shifts Tx1 and Tp1 to lower points and enhances the apparent activation energy. The structure of the hetero-amorphous Fe83.3Si4B8P4Cu0.7 alloy is more stable at as-quenched state. The crystallization process is mainly dominated by three-dimensional growth with various nucleation rate for the selected Fe84-xSi4B12-yPyCux (x:0 and 0.7, y:0 and 4) alloys. Both P and Cu alloying additions influence the nucleation process due to the existing of crystal-like clusters resulting from the contrary interactions among the constituent elements in as-quenched Fe83.3Si4B8P4Cu0.7 alloy. The precipitated phases for the selected alloys are similar during crystallization process. The grain size decreases to about 90nm from 200nm with addition of 0.7at.%Cu individually, and dramatically decreases to about 20nm with simultaneous addition of 4at.%P and 0.7at.%Cu to FeSiB alloys. The Tx1and Tp1shift to lower temperatures, and the apparent activation energies decrease with the increasing of Fe content in Fex(SiB)96-xP3Cu1(x=75,78,80,83 and 85) alloys. The crystallization process is mainly dominated by three-dimensional growth with various nucleation rate for the Fex(SiB)96-xP3Cu1(x=75,78,80,83 and 85) alloys. The crystallization phases are similar for all the alloys studied. The uniform nanostructure with grain size smaller than 20 nm are realized in Fex(SiB)96-xP3Cu1 (x=80,83 and 85) alloys which result from existing crystal-like cluster formed during melt-spinning. The size of grains ranges from 5 nm to 50 nm in annealed Fex(SiB)96-xP3Cu1 (x=75 and 78) alloys. A large quantity of amorphous matrix remains in annealed Fe75Si8B13P3Cu1 alloy even though its annealing temperature is the highest. FeSiBPCu alloys with higher Fe content exhibit better soft magnetic properties. Covercivity (Hc) of 12 A·m-1 and Js of 1.87 T are obtained in Fe85Si3B8P3Cu1 alloys. The W of the nanocrystalline Fe85Si3B8P3Cu1 and Fe83Si4B9P3Cu1 alloys is superior to the commercial Fe78Si9B13 alloy and silicon steel over the Bm range up to 1.7 T.FeSiBPCu alloys with Fe content higher than 85 at.% exhibit lower Hc and higher Js in as-quenched state and annealed state when P content is 2 at.%-3 at.%, Si content is lat.%-2at.%, Cu content is 0.7at.%-1.0at.%. Fe85.3B10P3Si1Cuo.7 alloys annealed at 753K for 600s obtain uniform microstructure with grain size of about 20 nm. The annealed exhibit excellent magnetic softness such as Js of 1.96T, Hc of 15A/m,μe of 19000,λs of 3×10-6, W lower than 1.0 over the Bm range up to 1.7 T. The type of precipitated phases during crystallization course doesn't change when the Fe85.3B10P3Si1Cu0.7 alloys annealed with magnetic field. The grain size becomes smaller in the Fe85.3B10P3Si1Cuo.7 alloys annealed with magnetic field, which may result from the difference of magnetic susceptibility between the precipitated phases and the as-quenched ribbons. FeSiBPCu alloys exhibit higher Js because Fe-B compounds could be restrained in the condition of annealing with magnetic field.The phase-decomposition sequence for Al-4wt.%Cu specimens aged at 403K with 10-T magnetic field is concluded as:supersaturated solid solution (ssss)→GP (I) zone→θ"-phase→θ'-phase→stableθ-phase. Quenched clusters aren't identified in the field specimens. The 10-T magnetic field shifts phase transformation point to lower temperatures and accelerates the aging course. The high magnetic field also has changed the size of theθ"-phase. It presents that high magnetic field strengthens the effect of the age-hardening because The micro-hardness of specimens applied 10-T magnetic field are always higher than the non-magnetic treated ones and the maximal increment reaches 19%.