Akihiro Makino

Ferromagnetic bulk glassy alloys

Abstract This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50xa0K before crystallization was obtained in Fe–(Al, Ga)–(P, C, B, Si), Fe–(Cr, Mo, Nb)–(Al, Ga)–(P, C, B) and (Fe, Co, Ni)–Zr–M–B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2xa0mm for the Fe–(Al, Ga)–(P, C, B, Si) system and 6xa0mm for the Fe–Co–(Zr, Nb, Ta)–(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe–(Al, Ga)–(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material.

Nb-Poor Fe-Nb-B nanocrystalline soft magnetic alloys with small amount of P and Cu prepared by melt-spinning in air

Abstract The effect of the addition of P and Cu to Fe85Nb6B9 alloy on an as-quenched structure and soft magnetic properties in a nanocrystallized state has been investigated. The Fe85Nb6B9 alloy melt-spun in air has an as-quenched structure of an amorphous phase and α-Fe grains with 20–45 nm in size. The coarse grains should still remain in the nanocrystallized structure, which deteriorates the soft magnetic properties. The simultaneous addition of 1 at.% P and 0.1 at.% Cu to the Fe85Nb6B9 alloy decreases the α-Fe grain size to nanoscale in an as-quenched state, and realizes a uniform crystallized structure with high saturation induction of 1.61 T as well as high permeability of 41,000.

Microstructure and properties of nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with low magnetostriction

We have investigated the microstructure–property relationship of nanocrystalline Fe85Zr1.2Nb5.8B8 and Fe85.5Zr2Nb4B8.5 soft magnetic alloys in order to understand the origin of drastic change in the permeability regardless of the zero magnetostriction in these two alloy compositions. Plan-view and cross-section transmission electron microscopy (TEM) observations showed strongly textured α-Fe particles on the free surface of the Fe85Zr1.2Nb5.8B8 alloy ribbon, while uniform nanocrystalline microstructure was observed in the Fe85.5Zr2Nb4B8.5 alloy ribbon. The high Zr content of the latter improves the glass forming ability, thereby suppressing the surface crystallization, resulting in higher permeability. By adding Cu in the Fe–Zr–Nb–B alloy, uniform nanocrystalline microstructure was obtained, from which superior soft magnetic properties with zero magnetostriction was achieved.

High coercivity of melt-spun (Fe0.55Pt0.45)78Zr2–4B18–20 nanocrystalline alloys with L10 structure

The structure and the coercivity (Hc) of rapidly quenched (Fe0.55Pt0.45)bal.Zr0–8B0–24 alloys prepared by the melt-spinning technique have been investigated. Ordered L10 Fe–Pt phase of 20–100 nm was obtained by rapidly quenching the melt for (Fe0.55Pt0.45)78Zr2B20 and (Fe0.55Pt0.45)78Zr4B18 alloys with high Hc of 341 and 649 kA/m in an as-quenched state, respectively. On the other hand, the (Fe0.55Pt0.45)78Zr4B18 alloy produced by Cu mold casting at a lower cooling rate than melt spinning is found to be composed of a mixed structure of Fe–Pt L10, ZrB12, PtZr and Fe3B phases and the alloy has much lower Hc of 74 kA/m than that of the melt-spun (Fe0.55Pt0.45)78Zr4B18 alloy. The lattice parameters (a and c) of the L10 phase in the melt-spun alloys suggest that Zr and B elements are contained in the L10 phase for the melt-spun alloys, which is possibly related to direct formation of the L10 structure by rapidly quenching the melt.

Compositional dependence of the soft magnetic properties of the nanocrystalline Fe–Zr–Nb–B alloys with high magnetic flux density

The compositional dependence of the soft magnetic properties of the nanocrystalline Fe–Zr–Nb–B alloys has been investigated. The magnetostriction (λs) and the grain size of the (Fe90Zr7B3)1−x(Fe84Nb7B9)x alloys, which are two typical ternary alloys mixed with the best soft magnetic properties, show intermediate values between those of the Fe90Zr7B3 with negative λs and the Fe84Nb7B9 with positive λs. However, the soft magnetic properties of the Fe–(Zr,u200aNb)7–B alloys are inferior to those of the Fe90Zr7B3 and the Fe84Nb7B9 alloys. The best soft magnetic properties have been obtained at Zr+Nb=6u200aat.u200a%. The Fe85.5Zr2Nb4B8.5 alloy shows a high μe of 60u2009000 at 1 kHz, a high Bs of 1.64 T, and zero λs, simultaneously. The alloy also exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is extremely lower than that of Fe–Si–B amorphous alloys. The nanocrystalline Fe–Zr–Nb–B alloys with improved soft magnetic properties are therefore suitable for pole transformers.

Structure and soft magnetic properties of bulk Fe-Al-Ga-P-C-B-Si glassy alloys prepared by consolidating amorphous powders

Abstract Structure and soft magnetic properties of the bulk Fe 70 Al 5 Ga 2 P 9.65 C 5.75 B 4.6 Si 3 glassy alloy prepared by pulse current sintering with uniaxial pressure were investigated. The sample consolidated in the temperature range of the supercooled liquid region consists only of amorphous phase and has a very high relative density of 99%. The flux density under applied field of 800xa0A/m ( B 800 ), maximum permeability ( μ max ) and coercive force ( H c ) for the sample sintered at 703xa0K in as-made state are 1.08xa0T, 7600 and 12.0xa0A/m, respectively. B 800 and μ max are improved to 1.17xa0T and 8000 by annealing at 723xa0K for 3.6xa0ks. The soft magnetic properties of the bulk Fe-based glassy alloy are superior to those of the bulk Fe-Si-B alloy consolidated amorphous powders. It is considered that the high relative density and good soft magnetic properties for the bulk Fe-based glassy alloy depend upon its high structural homogeneity originated from its high deformability, that is based on the viscous flow arisen from the appearance of supercooled liquid region.

Rapid-annealing effect on the microstructure and magnetic properties of the Fe-rich nanocomposite magnets

The rapid-annealing effect on the microstructure and magnetic properties of the nanocomposite Fe93-x-yCoxNb2(Nd,u200aPr)yB5 (x=0–20, y=5–7 at.u200a%) alloys produced by crystallization of an amorphous phase have been investigated. The melt-spun ribbons consist of an amorphous phase in the as-quenched state and the amorphous phase changes to a nanocomposite structure consisting mainly of bcc-(Fe, Co), (Nd,u200aPr)2(Fe,u200aCo)14B and residual amorphous phases after annealing at temperatures of 973–1023 K. The nanocomposite alloys exhibit improved values of remanence (Jr), coercive force (HcJ), and maximum energy product [(BH)max] upon annealing at a higher heating rate (α) in the temperature range corresponding to the primary crystallization temperature of bcc-Fe phase. As α increases, the grain sizes of each phase decrease, especially for the Nd2Fe14B phase, and the ratio of total surface area of the Nd2Fe14B to bcc-Fe phases (Shard/Ssoft), which are evaluated assuming each grain is a sphere, becomes close to 1 for the F...

Magnetic properties of zero-magnetostrictive nanocrystalline Fe}Zr}Nb}B soft magnetic alloys with high magnetic induction

Abstract The soft magnetic properties of the nanocrystalline Fe–Zr–Nb–B alloys have been investigated. The best soft magnetic properties have been obtained for the Fe85.5Zr2Nb4B8.5 alloy. The alloy shows a high permeability of 60,000 at 1xa0kHz, a high magnetic induction of 1.64xa0T and zero magnetostriction, simultaneously. The alloy also exhibits a very low core loss of 0.09xa0W/kg at 1.4xa0T and 50xa0Hz, which is extremely lower than that of Fe–Si–B amorphous. The nanocrystalline Fe–Zr–Nb–B alloy is therefore suitable for a core material for pole transformers.

As-quenched and nanocrystallized structure for Nb-poor Fe-Nb-B-P-Cu soft magnetic alloys melt spun in air

The as-quenched and nanocrystallized structures for Nb-poor Fe–Nb–B(–P–Cu) alloys melt spun in air have been investigated. The Nb-poor Fe85Nb6B9 alloy has the as-quenched structure composed of an amorphous phase and large α-Fe grains with 20–45 nm in size. The large α–Fe grains should remain after crystallization and result in a nonuniform nanocrystalline structure with the low permeability (μe) of 14u2009000 at 1 kHz. The simultaneous replacement of B by 1 atu2009% P and Fe by 0.1 atu2009% Cu for the alloy decreases the α-Fe grain size to nanoscale in an as-quenched state, and realizes a uniform crystallized nanostructure and good magnetic properties (μe=41u2009000 at 1 kHz and Bs=1.61 T) comparable to those of the typical Fe–M–B nanocrystalline alloys with a fully amorphous phase in an as-quenched state produced in a vacuum or Ar atmosphere. This result indicates that the precursor to the uniform nanostructure with high μe is not always a fully amorphous phase, and there is a possibility to realize the higher Bs materi...

Preparation of the bulk Fe–Al–Ga–P–C–B–Si glassy alloys in a ringed form by copper mold casting

Abstract The bulk Fe–Al–Ga–P–C–B–Si glassy alloy in a ringed form with the outer diameter of 10xa0mm, the inner diameter of 6xa0mm and the thickness of 1xa0mm was prepared by copper mold casting. This bulk alloy sample was composed of a single amorphous phase and had a supercooled liquid region of 59xa0K, which was the same as that of the melt-spun ribbon. The saturation magnetization, the coercivity and the maximum permeability of the bulk amorphous alloy sample in as-made state were about 1.2xa0T, 2.2xa0A/m and 110xa0000, respectively. These good soft magnetic properties of the bulk sample depend upon its high structural homogeneity based on large glass forming ability. In addition, the core loss for the Fe-based bulk amorphous alloy is lower than that of a nonoriented 3.5% Si steel in as-made state at the frequency of 50–60xa0Hz. It is, therefore, concluded that the Fe–Al–Ga–P–C–B–Si glassy alloy will be one of the useful industrial materials.