Bulk Amorphous Rods Research Articles

The Total Core Losses in Bulk Amorphous Rods of Fe60Co10Y8-xNi2+xB20 Alloys (Where x=0, 1)

The Total Core Losses in Bulk Amorphous Rods of Fe₆₀Co₁₀Y_8-xNi_2+xB₂₀ Alloys (Where x=0, 1)

Glass formability and soft magnetic properties of bulk Y–Fe–B–Ti metals

Abstract The Ti effect on the glass forming ability and the magnetic properties of Y–Fe–B–Ti bulk metallic glasses have been investigated. Substituting 2 and 4 at.% Ti for Fe or B in Y 6 Fe 72 B 22 alloy decreases the saturation magnetization ( σ s ) and deteriorates the glass forming ability, respectively. However, substitution of 2 at.% Ti for Y in Y 6 Fe 72 B 22 alloy induces larger supercooled region of 72.7 °C, which not only makes the bulk glassy rod as large as 3 mm in diameter, but also results in the superior soft magnetic properties of σ s = 126 emu/g, coercivity ( H c ) = 0.2 Oe and Curie temperature ( T C ) = 268 °C. Among all Y–Fe–B–Ti bulk amorphous rods, Y 4 Fe 72 B 22 Ti 2 displays the best glass forming ability and also the proper soft-magnetic properties.

Viscous flow behavior and thermal properties of bulk amorphous Mg 58Cu 31Y 11 alloy

The viscous flow behavior of the Mg 58Cu 31Y 11 bulk amorphous rods in the supercooled viscous region is investigated using differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA). Below the glass transition temperature, T g, a linear thermal expansion coefficient of 3 ± 1 × 10 −6 m/m K was obtained. In contrast, significant viscous deformation occurred as a result of a compressive load above T g. The onset, steady state, and finish temperatures for viscous flow, determined by TMA, are slightly different from the glass transition and crystallization temperatures measured by DSC. The appropriate working temperature for microforming as determined by the steady state viscous flow temperature is about 460–474 K. The effective viscosity within this temperature range is estimated to be about 10 7–10 9 Pa s, and it increases with increasing applied stress. The onset, steady state, and finish temperatures all decrease with increasing applied stress, suggesting accelerated crystallization in the present Mg 58Cu 31Y 11 under stress.

EFFECT OF HOT ISOSTATIC PRESSING ON MECHANICAL PROPERTIES OF Fe41Cr15Mo14C15B6Y2Co7 BMG

Fe -based bulk amorphous rods of 3 mm in diameter and a composition of Fe 41 Cr 15 Mo 14 C 15 B 6 Y 2 Co 7 were produced by copper mold casting. The as-cast amorphous rods contain a small (2%) fraction of pores. To close the pores, samples cut from the amorphous rods were hot isostatically pressed (hipped) at 863 K, which is in the supercooled liquid temperature range between the glass transition temperature and the crystallization temperature of the amorphous phase, and under a pressure of 200 Mpa. Microstructure examination of the hipped samples shows that hipping results in an increase of the density of the samples from 7.9 g/cm3 to 8.0 g/cm3, and a decrease of the porosity level from 2% to 1%, and that a very small fraction of unknown crystalline phase form. As a result of these microstructure change caused by hipping, the average room temperature compressive fracture strength of the bulk metallic glass (BMG) decrease from 3500 Mpa to 3000 MPa, while the strain to fracture changes little from 1.5% to 1.4%. The mechanisms of the effect of hipping on microstructure and mechanical properties of the Fe -based BMG are discussed.

Preparation, formation mechanism, and crystallization of Fe74Al4Sn2(PSiBC)20 bulk amorphous alloys

Bulk amorphous rods ( φ 1.0, 2.0 mm) of Fe 74 Al 4 Sn 2 P 11 C 4 B 4 Si 1 and Fe 74 Al 4 Sn 2 P 10 Si 4 B 4 C 2 alloys have been prepared by water-cooled copper mold method. The viscosities of these two alloys at high temperature ( T > T m ) were measured. The value of dimensionless parameter α was estimated, and β was calculated for Fe 74 Al 4 Sn 2 (PSiBC) 20 alloys. Large values of αβ 1/3 , T rg , and viscosities decrease the steady nucleation rate of the alloys, and favor the formation of bulk amorphous alloys. The single-stage crystallization process of Fe 74 Al 4 Sn 2 P 11 C 4 B 4 Si 1 amorphous alloy is: Amorphous→α-Fe+Fe 3 P+Fe 2 B+Fe 3 B+Fe 3 C, and the double-stage crystallization process of Fe 74 Al 4 Sn 2 P 10 Si 4 B 4 C 2 amorphous alloy is: Amorphous→amorphous′+α-Fe→α-Fe+Fe 3 P+Fe 2 B+Fe 3 B+Fe 3 C. The thermomagnetic curve of Fe 74 Al 4 Sn 2 P 11 C 4 B 4 Si 1 bulk amorphous alloy includes three stages: room temperature → T g → T x → higher temperature, and the thermomagnetic curve of Fe 74 Al 4 Sn 2 P 10 Si 4 B 4 C 2 bulk amorphous alloy comprises four stages: room temperature → T g → T x → T p1 → higher temperature. The initial precipitation of α-Fe results in the increase of saturation magnetization, while the simultaneous precipitation of Fe 3 P, Fe 2 B, Fe 3 B, and Fe 3 C leads to the decrease of saturation magnetization.

Thermal stability and glass forming ability of cast iron based CiPxB4.35 bulk amorphous alloys

The effect of P addition on the thermal stability and on the bulk glass forming ability (BGFA) of cast iron based CiPxB4.35 (x = 4.35, 8.65, 10 at%) amorphous alloys was investigated by calorimetric (DSC and DTA) measurements. The amorphous alloys were prepared by melt spinning and by centrifugal copper mold casting. The crystallization kinetics was studied by DSC in the mode of continuos times linear heating and it was found that, both the glass transition temperature, Tg and the crystallization peak temperature, Tp are shifted to higher temperatures with increasing heating rate. The partial replacement of Ci by P atoms increases the thermal stability of the amorphous state and the BGFA. Bulk amorphous rods with diameters of 1, 1.5, 2, 2.5, and 3 mm as well as sheets with 1 × 4 mm2 cross-section were prepared by centrifugal copper mold casting and the amorphicity of the melt-spun ribbons and of the mold cast rods was investigated by XRD, and HRTEM. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of Al on Bulk Amorphization and Magnetic Properties of FeSnPSiB Alloys

Structure and magnetic properties of melt-spun multi-component Fe78� xAlxSn2P12 Si4B4 (x ¼ 0, 3, 4, 5 at%) amorphous ribbons and copper-mold-cast rods were investigated. The improvement of thermal stability was recognized with the replacement of Fe by 3� 5 at% Al in these Sn-containing alloys. The super-cooled liquid region (� Tx), defined by (TxTg) where Tx is the crystallization temperature and Tg the glass transition temperature, increases from 46.5 K as x ¼ 3 to the maximum value 50.2 K as x ¼ 4. With increasing Al content, magnetic properties of annealed Fe78� xAlxSn2P12Si4B4 (x ¼ 3� 5 at%) amorphous ribbons are: saturation magnetization decreases from 1.22 to 1.18 T; coercive force decreases from 3.3 to 2.2 A/m, maximum permeability increases from 137000 to 208000, Curie temperature lowers from 591.1 K to 578.3 K; the electrical resistivity increases from 175 to 188 m� -cm; and core loss is about 0.14 W/kg (50 Hz, 1.1 T external magnetic field). Bulk amorphous rods with 1 mm diameter were successfully demonstrated for the composition Fe74Al4Sn2P12Si4B4 by a copper mold casting method. Due to the combination of good glass forming ability and superior soft magnetic properties, these alloys will find potential applications in industries.

Coercivity mechanism in mold-cast Nd 60Fe xCo 30− xAl 10 bulk amorphous alloys

The structural and magnetic properties of as-cast Nd 60Fe x Co 30− x Al 10 (5≤ x≤30) bulk amorphous rods were investigated. The samples exhibit inhomogeneous microstructure consisting of Fe-rich spherical regions separated by Nd-rich amorphous phase. The as-cast samples show large room temperature coercivities of ∼0.4 T. Thermomagnetic curves reveal two Curie temperatures T C1=32–52 K and T C2=470–500 K suggesting the presence of two magnetic phases. The coercivity increases monotonically with decreasing temperature up to T C1, and falls sharply with further decreasing temperature. Domain wall pinning mechanism for the temperature dependence of coercivity is proposed, which states that the phase with Curie temperature T C1 pins the domain walls at temperatures T> T C1. When the temperature decreases below T C1, the pinning centers order ferromagnetically resulting in a strong drop in coercivity. The presence of blocking temperatures T b in the zero-field-cooled (ZFC) samples suggests the presence of thermally activated magnetization processes connected with the domain wall pinning coercivity mechanism.

Compaction of bulk ferromagnetic Fe80P13C7amorphous alloys

When bulk ferromagnetic Fe80P13C7 amorphous rods of approximately 2-mm diameter are compacted together in a hot press, a variety of different microstructures, depending on the experimental conditions, are produced. The most intriguing microstructure is that two different bulk amorphous rods can be fused together perfectly at a temperature of 683 K and under a pressure of 2.5 to 4 GPa for a period of 5 min.

Effects of cobalt on sintering characteristics of iron-neodymium-boron alloys: K. Majima et al (Osaka University, Japan), J Japan Soc Powder and Powder Metallurgy, Vol 39, No 10, 1992, 855–859. (In Japanese)

The structural and magnetic properties of as-cast Nd60FexCo30−xAl10 (5≤x≤30) bulk amorphous rods were investigated. The samples exhibit inhomogeneous microstructure consisting of Fe-rich spherical regions separated by Nd-rich amorphous phase. The as-cast samples show large room temperature coercivities of ∼0.4 T. Thermomagnetic curves reveal two Curie temperatures TC1=32–52 K and TC2=470–500 K suggesting the presence of two magnetic phases. The coercivity increases monotonically with decreasing temperature up to TC1, and falls sharply with further decreasing temperature. Domain wall pinning mechanism for the temperature dependence of coercivity is proposed, which states that the phase with Curie temperature TC1 pins the domain walls at temperatures T>TC1. When the temperature decreases below TC1, the pinning centers order ferromagnetically resulting in a strong drop in coercivity. The presence of blocking temperatures Tb in the zero-field-cooled (ZFC) samples suggests the presence of thermally activated magnetization processes connected with the domain wall pinning coercivity mechanism.