Glass Forming Ability And Magnetic Properties Of CoFeBSiNbZr Alloy

In this paper, a series of different contents and diameters of cylindrical bulk amorphous alloys were prepared by copper-mold vacuum suction casting. The glass forming ability(GFA), magnetic properties, microhardness and plastic deformation behavior at the room temperature of these alloys were investigated by X-ray diffraction(XRD), differential scanning calorimetry(DSC), vibrating sample magnetometer(VSM), micro-hardness tester and nano-indenter. Furthermore, the microstructure and the crystallization process of the amorphous alloys were also studied in this paper. The main results are as follows.1. In Fe66-xCoxNd5B25Nb4(x=0,10,20,30,40) alloy, the amorphous alloy with diameter of 2 mm can be obtained when Co content is 20 at.%, and the supercooled liquid region ΔT of this alloy is 41 K. The saturation magnetization Ms of Fe66-xCoxNd5B25-Nb4(x=0,10,20,30,40) alloy is decreased firstly and increased subsequently with the increasing of Co content, rising from 82.72 A·m2·kg-1 in Co 0 at.% up to 102.97 A·m2·kg-1 in Co 10 at.%, then decreased with increasing of Co content, when the Co content is 40 at.%, the saturation magnetization Ms is minimum which is 67.70 A·m2·kg-1.2. The alloy of Co42Fe26B21Si6Nb5 shows good glass forming ability, the amorphous structure of the alloy with diameter of 3 mm can obtained by copper mold casting. The crystallization process of the amorphous alloy with diameter of 2 mm is divided into three stages. The saturation magnetization Ms of the alloy with diameter of 2 mm is 82.86 A·m2·kg-1, and the supercooled liquid region ΔT is 45 K.3. The alloys of Co47.6Fe20.4B21.9Si5.1Nb5-xZrx(x= 0~5) exhibit good glass forming ability(GFA), the amorphous structure with diameter of 3 mm can be obtained, while the GFA is decreased with the increase of Zr element. The alloys exhibit soft-magnetic properties, the crystallization process of alloys transform from two stages to three stages after adding element Zr. The microhardness can be improved with adding appropriate content of Zr, the microhardness is 1420 HV and the saturation magnetization Ms is 84.63 A·m2·kg-1 when the Zr content is 3 at.%.4. The Co47.6Fe20.4B21.9Si5.1Nb5-xZrx(x= 0~3) amorphous alloys show a high stability at room temperature, without occurring plastic deformation at a low loading rate. The amorphous structure contains two phases when the Zr content is 0 at.%. The amorphous at partial area contains microscale nanostallines, which is the reason for improving the microhardness when the Zr content is 3 at.%.5. The amorphous alloys of Co47.6Fe20.4B21.9Si5.1Nb5-xZrx(x= 0~3) can be completely crystallized when annealed at 1137 k for 10 min, and the crystallization process of alloys transform from two stages to three stages after adding elements of Zr. The crystallized phases are Fe2 B, Fe3 Si, Co7Fe3 and an unknown phase when the Zr content is 0~2 at.%, and crystallized phases are Fe2 B, Fe3 Si, Co21Zr2B6 and an unknown phase when the Zr content is 3 at.%. The alloys still has soft magnetic properties and the micorhardness had been improved in varying degree after annealed at different temperatures.