Effects Of The Structural Relaxation During Annealing On Properties Of FeBC(Cu,Mo) Soft Magnetic Alloys

Structural relaxsation will happen when Fe-based amorphous soft magnetic alloys are annealed below crystallization temperature and then lead to changes of microstructure and magnetic properties.In this thesis effects of annealing and Mo doping on the microstructure and magnetic properties of FeBC(Cu,Mo)alloys were investigated.Effects of annealing temperature and time on soft magnetic properties of Fe84B10C6 amorphous alloy were investigated.With the annealing temperature increasing to 493 K the easy magnetization axis of Fe84B10C6 amorphous ribbon tends to arrange parallel to the ribbon plane and then deviates from the ribbon plane as the annealing temperature increases further.Bsincreases gradually,and Hc decreases firstly and then increases showing a minimum at 493 K.The annealing time has similar effects on soft magnetic properties and the alloy annealed for 100 s has the minimum Hc.Fe84B10C6 alloy annealed at 493 K for 100 s shows the most excellent soft magnetic properties with Bs=1.65 T and Hc=5 A/m.Effects of Cu cluster tuning at amorphous state on soft magnetic properties of Fe83B10C6Cu1 alloy were investigated.With the pre-annealing temperature increasing from 548 K to 588 K,Cu atoms segregate and form the nuclei with similar size,the density of beneficial Cu clusters which can act as nucleation sites for ?-Fe in the crystallization process increases and the size distribution of Cu clusters is optimized.With the pre-annealing temperature increasing further to 608 K,Cu cluster size still shows a relative narrow distribution but its average value increases.Cu clusters in the alloy pre-annealed at 588 K show a best tuning.During the crystallization process,with the pre-annealing temperature increasing,the crystallinity increases,Bsincreases gradually,and Hcdecreases firstly and then increases sharply showing a minimum at 588 K.Fe83B10C6Cu1pre-annealed at 588 K for 10 min followed by annealing at 708 K for 100 s shows the most excellent soft magnetic properties with Bs=1.81 T and Hc=3.2 A/m.Effects of Mo doping on Cu cluster tuning and soft magnetic properties of Fe83-xB10C6Cu1Mox(x=0~1.25)alloys were investigated.Mo doping increases their amorphous forming ability,promotes the formation of beneficial Cu clusters and decreases the onset temperature of ?-Fe precipitation.With x increasing from 0.0 to 0.75,the density of beneficial Cu clusters increases,Cu cluster size distribution is optimized,and the optimal Cu cluster tuning is obtained at x=0.75.With x increasing to1.25,excessive Mo doping contributes to the Cu cluster growth,broadens the size distribution of Cu clusters and decreases the density of beneficial Cu clusters.With the crystallization temperatureincreasing Bsof Fe82.25B10C6Cu1Mo0.75 alloy increases gradually and Hcdecreases firstly and then increases showing a minimum at 693 K.The Bs and Hc of Fe83-xB10C6Cu1Mox(x=0~1.25)alloys both decrease firstly and then increase with x increasing.In these Mo doping alloys,Fe82.25B10C6Cu1Mo0.75 alloy shows the most excellent soft magnetic properties with Bs=1.75 T and Hc=2.1 A/m.