Fabrication of FePBNbCr glassy cores with good soft magnetic properties by hot pressing

Summary form only given. Since Fe-based FeAlGaPCB bulk glassy alloy (BGA) was firstly synthesized in 1995 [1], a number of Fe-based BGAs have been developed [2-7] in last two decades. These Fe-based BGAs have relatively high GFA, which leading to the formation of glassy alloy rods prepared by copper mold casting with much lower cooling rates than that of amorphous alloy thin ribbons produced by melt-spinning. However, their dimension is still restricted to be mm-order in diameters. The hot pressing process using glassy powder should be an alternative technique for the preparation of large-size BGAs. In this study, Glassy Fe₇₇P₇B₁₃Nb₂Cr₁ alloy powders were synthesized using raw materials in the particle size range below 100 μm by water atomization . The glassy powders were consolidated into cores with dimensions of 13 mm in outer diameter, 8 mm in inner diameter and 3 mm in thickness through sintering them at different temperatures under a pressure of 100 MPa by the hot pressing technique Fig.1 shows the XRD patterns of the cores sintered at different temperatures. It can be seen that when the sintering temperature below 771 K, which was the glass transition temperature of the powder, only broad peaks without a crystalline peak can be seen, indicating the formation of a glassy single phase of the cores. While increasing the sintering temperature to above 791 K, it is crystallized and the phase is Fe₃(B,P), a-Fe and some unknown phase, which will destroy the soft magnetic properties of the cores. Table I summarizes the soft magnetic properties and core loss of the cores compressed at different temperatures. It can be seen that the core sintered at 771 K exhibits good soft magnetic properties, i.e., high saturation magnetic flux density B_s of 1.13 T, low coercive force H_c of 50 A/m, relative high effective permeability u_e of 1200 at 1 kHz under a field of 1 A/m, - ow core loss P of 25.8 W/kg at 10 kHz under the maximum magnetic flux density of 0.1 T . The synthesis of Fe-based glassy cores with good magnetic properties is encouraging for future applications as functional materials .