&-The change in magnetic properties with B content and ameahg tempe-ature was investigated for FeB-M-Cu (M = Hf, Zr, Nb) alloys In the high B alloys over 8 at% B, the optimum ameahg temperatures revealing the excellent soft magnetic properties were below the aystalliation temperatures. The annealed d~s h u c t u r e had ultrafine &-Fe phase grains with a diameta of 5-7 nm and a considerably hwh fraction (30-50 vol.%) of interfacial amMphous phase. For these alloys, very low core loss and high effective pameability were obtained in the frequency range up to 1 MHz. These behaviors were interpreted to be due to their hybrid minostructure and high electrical resistivity,
I . INTRODUC~ONIt has been known that if &-Fe structure with fine grain size, of about 10 to 20 nm, is famed by the crystallization of precursor amorphous alloys such as FeZrECu and FeCuNbSiB alloys, good soft magnetic properties with large magnetization as well as high effective permeability can be obtained [11,[21. Recently, we reported that the amorphous F%Bl&M,. system alloys with high baon content of 10 at.% possessed good soft magnetic properties at high frequencies [31. We anticipated that microstructural hybridization of these alloys into nancuystalline and amorphous structure can give a good soft magnetic property at high frequencies as well as high saturation magnetization.In this s M y , the change in magnetic properties and microsbctures with B content and m d i tenperam was investigated in the amorpholls Fe-B-M-Cu (M = €If, Zr, Nb) alloys.
EXPERIMENTAL PROCEDUREAmcxphous alloys were prepared in an argon a m p h e r e by the single-roll melt spinning technique. The resulting ribbons were about 20 p thick and 1.5-2.5 mm wide. They were w a d onto GI bobbins with inner diameter of 21 mm, and subsequently annealed for 1 h in vacuum at variws temperahws ranging from 470 to 710C. X-ray diffraction measurements wen? carried out by using Cu K a radiation. The microstructures of annealed samples and crystallization behaviors of amorphous alloys were examined by transmission electron microscopy ('EM) and differential thermal analyzer (DTA). The effective permeability ( p J was measured at 1 kHz under 10 mOe with an impedance analyzer. Measurements of electrical resistivity ( p ) and c o~e loss were carried out by dc fourprobe technique and ac B-H analyzer, respectively.Magnetic induction at 10 Oe (BIOI and coercive force (Hc)were measured with a dc hysteresis loop tracer. Manuscript received Mwch 31,1994 36 .-.-a, 12 a .-a, L G 4 o M 5 H f ' 0 4 2 4 6 8 10 12 Boron Content, X ( a b ) Fig. 1 Effective pameability as a function of B content Fe&3xM7Cul alloys. for III. RESULTS AND DISCUSSION Fig. 1 shows the change in p e as a function of B content foc F~SZ-~&M~CUI (M = Hf, Zr, Nb) (at%) alloys subjected to optimum annealing. Maximum p e curves of F~-x~H f~u~ and Fm-x&Z&ul alloys split into two stages with the peaks at 4 and 10 at.% B. As well known, the high value of p e at 4 at% B seems to be related to the basic " i s m for the good soft magneti...
