Preparation Process Of Bulk Iron-based Amorphous Nanocrystalline Magnetic Materials By Spark Plasma Sintering Technology

The soft magnetic material is a kind of magnetic materials with high saturationmagnetic induction intensity, high permeability and low coercive force. Among them, theiron-based amorphous and nanocrystalline soft magnetic material with excellent softmagnetic, mechanical properties and low cost has important and extensive applicationprospect in the field of functional materials and structural engineering materials. However,due to the limitation of glass formation ability, the composition of amorphous andnanocrystalline alloy was single and the size was small, whicn has severely restricted thewidely use of the iron-based amorphous and nanocrystalline alloy in industry and dailylife. Therefore, the exploration of the wider iron-based amorphous and nanocrystallinealloy system and a new preparation technology of bulk amorphous and nanocrystallinealloy have important significance.The Fe-Si-B series alloys were as the research subjects in this paper. Thecompositions were designed by the element substitution method, the iron-based magneticamorphous and nanocrystalline alloy powders were prepared by mechanical alloying (MA)technology, the bulk iron-based amorphous and nanocrystalline magnetic materials werefabricated by spark plasma sintering (SPS) technology. It has researched the influence ofSi and transition metal M (M=Zr, Nb, Mo, Cu) elements on the amorphous forming ability,the thermal stability and the magnetic properties. It has researched the influence of thesintering temperature, sintering pressure, heating rate and holding time on the bulksintering alloys in SPS sintering process. It has researched the influence of M element onthe microstructure, mechanical and magnetic properties of the SPS sintering bulk alloys.The Fe78Si13B9、Fe75M(M=Zr, Nb, Mo)3Si13B9、Fe77Cu1Si13B9and Fe74Cu1M3Si13B9amorphous alloy powder were prepared successfully by mechanical alloying technology.The research showed that Si element plays an important role in formation of amorphousalloy in Fe-Si-B alloy system, the Fe85Nb6B9and Fe84Cu1Nb6B9alloys without theaddition of Si element can only form nanocrystalline alloy powder by MA technology. Theaddition of Zr, Nb, Mo and Cu element can shorten the time of Fe-Si-B series alloyformed amorphous alloy in the process of MA. Among them, the Zr and Nb elements can improve the thermal stability of the amorphous alloy powder, but the Mo and Cu elementsare contrary. The amorphous alloy powder prepared by MA has the typical intrinsicmagnetic properties of soft magnetic material. The coercive force Hcof the eight kinds ofamorphous alloy powders from small to large in the order is: Fe77Cu1Si13B9<Fe74Cu1Zr3Si13B9<Fe74Cu1Nb3Si13B9<Fe75Zr3Si13B9<Fe75Nb3Si13B9<Fe78Si13B9<Fe74Cu1Mo3Si13B9<Fe75Mo3Si13B9.In the process of SPS, the sintering temperature, sintering pressure, heating rate andthe holding time have a significant effect on the organization structure, desity, mechanicaland magnetic properties of the sintering bulk alloys. Among them, the increase of sinteringtemperature can significantly improve the density, compressive strength and saturationmagnetization of the sintering bulk alloys and make the coercive force and resistivitydecreased. But if the sintering temperature is too high, a lot of BCC α-Fe(Si) solid solutionand six-party structure Fe2B compounds could be precipitated in the sintering bulk alloys,which can deteriorate the mechanical and magnetic properties. The optimum sinteringtemperature of the alloy powders is at the crystallization peak temperature Tp. The increaseof sintering pressure can improve the density, compressive strength, hardness and themagnetic properties of the sintering bulk alloys, but the increase of pressure can lead tothe crystal transition of the amorphous in sintering bulk alloys. The increase of heatingrate can inhibit the crystallization of amorphous phase, make the amorphous powder easilyformed amorphous phase or homogeneous dimension nanocrystalline phase in thesintering process and make the mechanical and magnetic properties of the sintered bulkalloys improved. The extension of the heat preservation time can promote thecrystallization of the amorphous phase and make the grain size of the crystallization phaseincreased. At the same time, the longer heat preservation time can make the mechanicaland magnetic properties of the sintered bulk alloys seriously deteriorated. The best heatpreservation time of the Fe77Cu1Si13B9is about10min.The Fe78Si13B9、Fe75M(M=Zr, Nb, Mo)3Si13B9、Fe77Cu1Si13B9and Fe74Cu1M3Si13B9bulk amorphous and nanocrystalline magnetic materials were faricatied successfully bySPS technology. The research showed that Zr and Nb elements can significantly inhibit thecrystallization transformation of the amorphous powder in the SPS sintering process, but Mo and Cu element are contrary. At the same time, the addition of Zr、Nb and Mo elementmakes the soft magnetic properties of the bulk sintering alloys worse. Among them, theinfluence of Mo element is most significant. The Cu element can have the effect of finegrains in the sintering process and make the density, mechanical and soft magneticproperties of the sintered bulk alloys improved. The coercive force Hcof the eight kinds ofsintering bulk alloys from small to large in the order is: Fe77Cu1Si13B9<Fe74Cu1Zr3Si13B9<Fe78Si13B9<Fe74Cu1Nb3Si13B9<Fe74Cu1Mo3Si13B9<Fe75Zr3Si13B9<Fe75Nb3Si13B9<Fe75Mo3Si13B9. Among them, the compressive strength, saturation magnetization andcoercivity of the Fe77Cu1Si13B9bulk alloy are2.3Gpa,158.65emu/g and28.4Oe,respectively. They are significantly better than the Fe75Mo3Si13B9bulk alloy, whichare1.6Gpa,148.42emu/g and47.49Oe, respectively.