Formation of Fe73.5Cu1Nb3Si13.5B9 nanocrystalline soft magnetic bulk alloys in high pressure

Fe73.5Cu1Nb3Si13.5B9 soft magnetic alloy powders and its bulk alloys were prepared by the mechanical alloying (MA) method and cryogenical high pressure solidification process. Phase components, average grain size, thermal stability of powders and relative density of bulk alloys of the samples were analyzed by XRD, DSC, SEM and TEM. The results showed that (1) after MA for 70 hours, bcc single phase alpha-Fe nanocrystalline supersaturate solid solution powders with average grain size 9.5nm can be obtained; (2) four exothermal peaks with different intensity appeared in DSC heating-up curves, these peaks corresponded to structural relaxation of distorted nanocrystalline supersaturate solid solution, crystallization of small quantity amorphous and phase precipitation of supersaturate solid solution, respectively. Phase precipitation of supersaturate solid solution included two stages; (3) under the sintering conditions of P=5.5GPa, t=5min and P-w=980W, single phase a-Fe nanocrystalline bulk alloys with 98.4% relative density and about 12.5nm average grain size can be obtained, soft magnetic properties of the bulk alloys were specific saturation magnetization M-s = 1.71 X 10(-7) Wb(.)m/g, coercive force H-c = 8.22 x 10(3) A/m.