Sintering and magnetic properties of mechanical alloying Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 nanocrystalline powder

The influence of spark plasma sintering and high-pressure sintering technique on microstructure and magnetic properties of bulk alloys of MA Fe_~73.5 Cu_1Nb_3Si_~13.5 B_9 nanocrystalline powder were investigated. The results show that after milling for 70h, the single phase α-Fe nanocrystalline supersaturate solid solution powder with average grain size 9.5nm and bcc structure can be obtained. In DSC heating-up curve of MA powder, four exothermal peaks with different strength appear, which are corresponding to the structure relaxing process of distorted nanocrystalline supersaturate solid solution, crystallization process of trace amorphous phases and phase precipitation of supersaturate solid solution, respectively. The precipitation process of supersaturate solid solution is decided into two stages. Under the SPS sintering conditions at p=30MPa, t=5min, when sintering temperature is 1050℃, nanocrystalline (100nm) bulk alloy with relative density of 99% and main phase of α-Fe can be obtained, the magnetic properties of bulk alloy are: B_s=1.34T, H_c=7.34kA/m. Under the high-pressure sintering conditions of p=5.5GPa, t=5min, when P_w=1150W, single phase α-Fe nanocrystalline (21.4nm) bulk alloy with relative density of 99.1% can be obtained, the magnetic properties of which are: B_s=1.14T, H_c=8.22kA/m.