As-spun Ribbons Research Articles

Structural and Magnetic Properties of Sm(CobalFe0.1Ni0.12Zr0.04B0.04)7.5 Melt Spun Ribbons

We have investigated the structural and magnetic properties of Sm(Co0.70Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. The arc-melted bulk samples have been used to obtain ribbons at 37 up to 55 m/sec while annealing has been performed in argon atmosphere for 30-75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure has been determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transforms into 2:17 and 1:5 phases. TEM analysis shows a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe are obtained from hysteresis loops traced at non-saturating fields. The coercivity decreases as temperature increases, but it is high enough to maintain values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increases, as high as 7.2 MGOe, for melt-spun ribbons produced at higher wheel speed.

Desorption of hydrogen from Ti–Zr–Ni hydrides using a mass spectrometer

We have performed thermogravimetry (TG) and mass-spectrometry measurements of hydrogen desorbed from fully and partially hydrided ternary Ti–Zr–Ni amorphous, quasicrystalline and crystalline alloys, with four different initial compositions, where the Ti/Zr ratio ranged from 1 to 2.4. The icosahedral, quasicrystalline Ti–Zr–Ni samples were obtained using the melt-spinning technique, and with subsequent annealing of these ribbons at 700 °C for 2 h in vacuum we were able to obtain a mixture of crystalline C14 Laves and α/ β solid-solution phases. In addition, using subsequent mechanical alloying we produced amorphous powders of Ti–Zr–Ni from the as-spun ribbons. These various samples were then hydrided and analyzed by TG and mass spectrometry. The TG measurements provided us with the mass% of desorbed hydrogen, whereas the mass-spectrometry revealed information about the hydrogen desorption temperatures in the material. Despite the fact that the amorphous and icosahedral samples undergo some crystallization during the desorption measurements, the resulting mass spectra were different and were closely related to the alloy's structure. In contrast, the shapes of mass spectra were less affected by the composition, the total amount of desorbed hydrogen and the loading pressure.

Microstructure-hardness relationship of Al–(L1 2)Al 3Ti nanocomposites prepared by rapid solidification processing

We report here successful synthesis of Al-based nanocomposites with L1 2–Al 3Ti particles in binary Al–Ti (4.1, 5, 8.3, 10, 15 and 20% Ti) and ternary Al-1.6Ti-0.5Cr, Al-3.2Ti-1.0Cr and Al-6.3Ti-2.0Cr alloys, by rapid solidification processing. The microstructure of all the alloys consists of uniform distribution of nanocrystalline L1 2–Al 3Ti intermetallic in ultra-fine α-Al matrix. The volume fraction of L1 2–Al 3Ti phase in the as-spun ribbons was found to increase with the Ti content in the binary alloys with exception of Al-20% Ti alloy, which formed equilibrium DO 22–Al 3Ti. The α-Al grains were measured to be in the size range 0.5–1.0 μm embedded with L1 2–Al 3Ti particles of ∼50 nm diameter. Nanoindentation as well as microhardness of nanocomposites in binary Al–Ti alloys measure hardness value of 3.75 GPa (367 VHN). The nanocomposites formed by rapid solidification processing retain about 70–85% of its room temperature hardness even at 500 °C for 100 h, while the hardness of conventional Al alloys such as 2017 is almost lost at 350 °C in 30 min.

Shape Memory Behavior of Ti-Rich Ti-Ni-Cu Melt-Spun Ribbons

Crystal structures and shape memory properties of Ti-rich Ti52Ni23Cu25 (at.%) ribbon annealed at 450°C for 10 min and 1 h were investigated by X-ray diffraction and dynamic mechanical analyzer. As-spun ribbon was full amorphous and its crystalline peak temperature is 455.4°C. The annealed ribbon is crystallized with strong preferential (110)-B2 orientation. It shows a well-defined shape memory effect and the transformation hysteresis for the annealed ribbon under an external load in the range of 3-9 N is about 38.5°C. With annealing time increasing from 10 min to 1 h, the maximum of transformation strain under the external stress decreases from 1.93% to 1.7%. The temperature dependence of the external stress increases from 0.3 N/°C to 0.43 N/°C. The residual plastic strain is up to about 0.4% at a load of 9 N.

Quasicrystalline effects on the mechanical relaxation behavior of a Ti 45Zr 16Ni 9Cu 10Be 20 metallic glass

In order to investigate the effects of quasicrystalline phase on the mechanical relaxation behavior of a metallic glass, dynamic mechanical properties of as-spun and heat treated Ti 45Zr 16Ni 9Cu 10Be 20 ribbons were measured. From the temperature dependence of the shift factor, obtained by the master curve of tan δ, the activation energies for sub- T g and α-relaxation of both ribbons were calculated and their relaxation mechanisms were investigated. The activation energy for sub- T g relaxation of heat treated ribbon which contains the quasicrystalline phase in the amorphous matrix showed higher value than that of the as-spun amorphous ribbon, while the activation energy for α-relaxation of both ribbons showed similar value. The activation energy for the sub- T g relaxation of the heat treated ribbon was even higher than that for the α-relaxation of it. The high value of the activation energy for the sub- T g relaxation of a heat treated ribbon can be said to be ascribed to the highly cooperative motions associated with the phason-type atomic rearrangement of the quasicrystalline phase embedded in the amorphous matrix of the heat treated Ti 45Zr 16Ni 9Cu 10Be 20 ribbon.

Structure and magnetostrictive properties of melt-spun Pr(Fe 0.4Co 0.6) 1.93 alloys

Pr(Fe 0.4Co 0.6) 1.93 ribbons were prepared by a melt-spinning method. Their structure and magnetic properties are investigated as functions of wheel speed and annealing temperature. The as-spun ribbon consists of a Pr(Fe, Co) 2 cubic Laves phase and an amorphous phase at a wheel speed of v≥35 m/s, while the non-cubic phases of PuNi 3-type and rare earth appear when the speed lower than 30 m/s. A single Pr(Fe, Co) 2 phase with MgCu 2-type structure has been synthesized by the process for the wheel speed of v≥35 m/s and subsequent annealing at 500 °C for 30 min. The epoxy/Pr(Fe 0.4Co 0.6) 1.93 composite has been produced by a cold isostatic pressing technique, and the magnetic properties have been investigated. The composite rod sample possesses good magnetostrictive properties, i.e., a large magnetostriction ( λ a= λ ∥− λ ⊥) of 710 ppm at 800 kA/m and a dynamic coefficient d 33 of 0.67 nm/A at 100 kA/m, and is of practical value.

Crystallization of single-phase nanocrystalline Nd 10.8Dy 1.5Fe 79.7(NbZrCu) 2.0B 6.0 ribbons

The crystallization of single-phase nanocrystalline Nd 10.8Dy 1.5Fe 79.7(NbZrCu) 2.0B 6.0 ribbons has been investigated. The as-spun ribbons are mainly composed of an amorphous matrix with a small amount of α-Fe, Nd 2Fe 14B and/or other crystallization phases. Cu-enriched clusters with different sizes have been found in the as-spun ribbons. These clusters almost disappear after crystallization, which can possess effects on the refinement of grains.

Effect of Ni on the microstructure and precipitate phases of Fe 78Si 9B 13 glassy alloy

The (Fe 0.78Si 0.09B 0.13) 100− x Ni x glassy alloys ( x = 0, 2, 3 and 5) have been investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Vickers microhardness test, transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The experimental results show that the addition of Ni has not only promoted the growth of α-Fe phase and the precipitate of Fe–B compounds but also facilitated the dissolution of silicon in the α-Fe phase. For the as-spun ribbon with x = 5, the microhardness ( H v) of the ribbon with super heating (SH) treatment is lower than that of the ribbon without SH; and the H v of the free side is lower than that of the wheel side of the same ribbon. The saturation magnetization ( M s) of the as-spun (Fe 0.78Si 0.09B 0.13) 95Ni 5 ribbon with SH is higher than that of the ribbon without SH. The variation of the H v and M s is explained by the free volume model which is related to the two structure model in Fe-based glassy alloys, as well as the change of the B content in the amorphous matrix.

Microstructure evolution in the rapidly quenched Fe78Si9B13 ribbons

We report microstructure evolution in as-spun Fe 78 Si 9 B 13 ribbons under various wheel speeds ( s ), which was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). With decreasing s , the volume fraction of the residual amorphous phase ( V a ) in the as-spun ribbons decreases gradually, and the total exothermic heat of the crystallization in the DSC curves also decreases, but the ratio of the exothermic heat of the second crystallization to the first one is on the contrary. α-Fe is found in the ribbon with s of 32.9 m/s, while α-Fe, eutectic α-Fe+Fe 2 B, and Fe 3 Si phases are found in ribbons with s of 25.6 and 18.3 m/s. The phase precipitating behavior in cooling processes is well consistent with the annealing process in the literatures.

High saturation magnetization and microstructure in melt-spun Fe–P ribbons

A high saturation magnetization, Bs, of 1.9 T and coercivity, Hc, of 0.5 Oe were obtained in melt-spun ribbons of Fe–0.63 at.% P after magnetic annealing at 400 °C. Transmission electron microscopy studies revealed the presence of coarse Fe3P precipitates in as-spun ribbons, while these precipitates were found to be finer in annealed samples. The coercivity variation in the samples processed at various conditions was explained by the formation of the Fe3P precipitates.

Influence of quenching rate on the structural, soft magnetic and magnetoimpedance properties of melt-spun Co 69Fe 7Si 14B 10 alloy

Melt-spun ribbons of Co 69Fe 7Si 14B 10 alloy have been prepared at different wheel speeds viz. 47, 34 and 17 m/s and investigated for structural and magnetic properties. Degree of amorphicity in the as-spun ribbons is found to increase with wheel speed. Amorphous phase crystallizes in two stages producing Co 2Si, Co 2B and CoSi phases on annealing. Increase in wheel speed improves soft magnetic and magnetoimpedance properties due to decrease in perpendicular anisotropy which is associated with stripe domain formation. On annealing soft magnetic properties and magnetoimpedance deteriorate due to the formation of crystalline phases.

Synthesis and magnetic properties of melt-spun high Pr-content magnetostrictive alloys

Abstract Pseudobinary high Pr-content Tb1−xPrx(Fe0.4Co0.6)1.93 (0.70≤x≤1.00) magnetostrictive alloys have been fabricated by a melt-spinning method. The effects of the composition, spinning, and annealing processes on the structure, thermal stability, and magnetic properties are investigated. At a wheel speed of v≤30 m/s, the as-spun ribbons consist of a mixture of (Tb,Pr)(Fe,Co)2 cubic Laves phase and some non-cubic phases. A single (Tb,Pr)(Fe,Co)2 phase with MgCu2-type structure is formed with the process for the speed of v≥35 m/s and subsequent annealing at 500 °C for 30 min. The lattice parameter of the Tb1−xPrx(Fe0.4Co0.6)1.93 Laves phase increases from 0.7354 nm for x=0.70 to 0.7384 nm for x=1.00 and approximately follows the linear Vegard's law. The Curie temperature decreases, while the saturation magnetization increases as increasing Pr content. The Pr-rich alloys possess the relatively lower coercivity and the faster saturation of magnetostriction as compared with the Tb-rich alloys, which can be understood by their lower magnetic anisotropy.

Microstructures and magnetic properties of rapidly solidified Ni54Fe27−2xGa19+2x ferromagnetic Heusler alloys

Rapidly solidified Ni54Fe27−2xGa19+2x (x=0, 1, 2, 3, and 4) ferromagnetic shape memory alloys were made by melt-spinning with variation of Fe and Ga contents to report on the martensitic phase transformation, microstructures, and magnetic properties. Rapid solidification produced pure L21 phase by preventing the formation of γ-phase. To study the effect of heat treatment on the phase transitions, microstructures, and the magnetic properties, the melt-spun ribbons were partly heat treated at different temperatures of 800, 900, 1000, 1100, and 1200 K with holding times of 5, 10, and 15 min followed by either water quenching or air cooling. The microstructures of the as-spun ribbons as revealed by electron microscopy studies exhibited a gradual transition from cellular to dendritic structure with increasing Ga concentration and with the presence of some internal martensitic twin bands at higher Ga content. The ribbons exhibited very low coercivity with high saturation magnetization, as high as ∼87 emu/g (decreasing with Ga concentration). The above-ambient Curie temperature (TC) and the subambient martensitic transition temperature (Tm) were observed to be ∼320 and ∼195 K, respectively. At higher heat treatment temperatures formation of ductile γ phases was observed.

Electrochemical hydrogen storage characteristics of nanocrystalline and amorphous Mg 20Ni 10− xCo x ( x = 0–4) alloys prepared by melt spinning

Nanocrystalline and amorphous Mg 2Ni-type electrode alloys with nominal compositions of Mg 20Ni 10− x Co x ( x = 0, 1, 2, 3, 4) were synthesized by melt-spinning technique. The microstructures of the as-spun alloy ribbons were characterized by XRD, SEM and HRTEM. The electrochemical properties of the alloys were measured. The experimental results showed that the substitution of Co for Ni did not change the major phase of Mg 2Ni, but it led to the formation of secondary phase MgCo 2. No amorphous phase formed in the as-spun alloy ( x = 0), whereas the as-spun alloy ( x = 4) held a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni significantly enhances the glass forming ability of the Mg 2Ni-type alloy. The substitution of Co for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the cycle stability, for which the increased glass forming ability by Co substitution is mainly responsible.

Effect of Fe on the structure and magnetic properties of Sm–Co–Cu–Fe–Zr melt-spun ribbons

The Sm 12Co 60− x Cu 6Fe 19+ x Zr 3 ( x = 0–10) ribbons are prepared by melt-spun at 20 m/s, and the effects of Fe content on structure and magnetic properties of the ribbons are studied. It is observed that all as-spun ribbons are composed of Sm(Co,M) 7 phase and small amount of α-Fe phase. Fe addition does not change phase composition of the ribbons. However, Fe can supersaturatedly dissolve in Sm(Co,M) 7 and constrain the amount of α-Fe in the melt-spun ribbons. 1:7H phase in the x = 3 ribbons starts to decompose when the ribbons are annealed above 800 °C, that is, SmCo 1:7H → SmCo 1:5H + SmCo 2:17R + α-Fe. α-Fe is shown as precipitated phase, and all these precipitated phases are distributed in the form of fine needles. Magnetization of all melt-spun ribbons is determined by nucleation field; And magnetization of the x = 3 ribbons annealed at different temperatures is determined by different coercivity mechanisms. In the maximum applied field of 20 kOe, x = 1 ribbons annealed at 800 °C gets the highest coercivity of 2.262 kOe; x = 5 as-spun ribbons gets the highest remanence of 36.94 emu/g.

Microstructure and Magnetic Properties in Fe61Co9−x Zr8Mo5W x B17 (0 ≤ x ≤ 3) Glasses and Glass-Matrix Composites

By systematically investigating the Fe61Co9−xZr8Mo5WxB17 (0 ≤ x ≤ 3) melt-spun ribbons and copper-mold cast cylinders with 2-mm diameter, we attempt to discover the effect of tungsten on the microstructure and magnetic properties of the Fe-based glass formers. It was found that all as-spun ribbons are fully amorphous and their characteristic distance δa has an increasing tendency with tungsten content (cW). The precipitates in the as-cast cylinders change from the ferromagnetic phases (Fe23Zr6 + Fe2Zr + Fe2B + Fe8B) plus α-Fe to the nonmagnetic phases (ZrB12 + W2B5) plus α-Fe with increasing cW. The averaged characteristic distance δc of the precipitates formed in the casting and annealing processes increases with cW, consistent with the δa of the ribbons. The temperature and heat of the first crystallization for the as-prepared ribbons and cylinders (Tp1 and ΔH1) also increase with cW. The magnetization and Curie temperature of the as-prepared ribbons and cylinders decrease with cW, while the coercivity of the as-prepared samples is obviously dependent on the volume fraction of the precipitates formed in the casting process (CP). These results indicate that tungsten can tune the fractions of the face-centered-cubic/random-close-packed (fcc/rcp) and body-centered-cubic (bcc) Fe-rich structural units in the undercooled melts of the Fe-based glasses.

Development of Ni-Pd-P-B Bulk Metallic Glasses with High Glass-Forming Ability

A small amount of boron was added to Ni60Pd20P20 and Ni65Pd15P20 alloys. The alloys containing 3 at% boron showed improved thermal stability and glass-forming ability. The supercooled liquid region of as-spun ribbons was enlarged by about 10 K for both Ni60Pd20P17B3 and Ni65Pd15P17B3 alloys. The critical diameters for glass formation were increased up to 15 mm for Ni60Pd20P17B3 and 10 mm for Ni65Pd15P17B3, respectively. The reason of the minor B addition leading to the significant improvements of thermal stability and glass-forming ability was investigated.

High coercivity Nd2Fe14B/α-Fe nanocomposite magnets

High coercivity Nd 2 Fe 14 B/α-Fe nanocomposite magnets have been prepared with the addition of 5% Nb elements. The amorphous formation ability and thermal stability of as-spun ribbons were increased. A fine and uniform microstructure with 10 nm was achieved after the ribbons with normal composition (Nd 0.9 Dy 0.1 ) 9.5 Fe 74 Co 5 Nb 5 B 6.5 were annealed at 710 °C for 4 min, which enhances the interaction coupling between grains and improves the coercivity greatly. The results of three-dimensional atom probe (3DAP) revealed that Nb–Fe–B intergranular phase with the ratio of Nb:Fe:B=1:1:1 existed at the boundary of grains, suppressing the grain growth during crystallization process. The coercivity of ribbons with 5at% Nb elements reaches to 1115 kA/m, which is the much higher value for the ribbons with 9.5at% total rare earth for Nd 2 Fe 14 B/α-Fe nanocomposite magnets.

Crystallization and corrosion resistance of as-spun (Al 86Ni 9La 5) 98Zr 2 amorphous alloy

(Al 86Ni 9La 5) 98Zr 2 amorphous alloy ribbons were successfully prepared by using the melt spinning technique, and the crystallization behavior of the amorphous ribbons was investigated. The result indicated that the amorphous alloy exhibited a three-step crystallization process with crystallization stages starting at 545 K, 606 K and 641 K, respectively. By annealing treatment at the different temperatures, the samples with the different crystallization extents were obtained. The potentiodynamic polarization measurements on these samples revealed that the sample with the primary crystallization exhibited higher corrosion resistance than that of the as-spun amorphous ribbons, while the secondary and complete crystallization was detrimental to the corrosion resistance of the alloy.

Phase transformation sequence and magnetic properties of melt-spun SmCo-based alloy after isochronal heat treatment

The phase transformation sequence, microstructure and compositions, and magnetic properties for a melt-spun Sm(Co0.68Fe0.2Cu0.1Zr0.02)7.5 alloy after isochronal heat treatments have been studied by using x-ray diffraction, transmission electron microscopy, three-dimensional atom probe (3DAP), and magnetometry. The as-spun ribbons had a single phase with the Cu7Tb structure. After being aged at 720°C, the single phase decomposed into two major phases: 2:17R and 1:5H, and one minor CoFeZr-rich phase. The formation of the Z-phase happened after the cellular structure, requiring a higher temperature than that for the cellular structure. The 3DAP analysis showed that Zr was depleted from the 2:17R and 1:5H phases by a half while the other elements remained almost unchanged when the aging temperature increased from 720to840°C. In contrast to the sintered permanent magnets, Cu was enriched in the 1:5H phase with a much higher concentration (>40at.%). The Cu enrichment also occurred at the boundary of the Z-phase. The coercivity achieved was Hc=4.34kOe following aging at 720°C. The highest maximum energy product, (BH)max, was 6.48MGOe after aging at 800°C and the remanence to saturation magnetization ratio, Mr∕Ms, was 0.69. This relatively low Hc and high Mr∕Ms ratio may be a consequence of the formation of a significant volume fraction of the CoFeZr-rich nanocrystalline phase.