Single Roller Melt Spinning Research Articles

Differences in microstructure and magnetic properties between directly-quenched and optimally-annealed Nd–Fe–B nanocomposite materials

Melt-spun Nd 9.5Fe 81Zr 3B 6.5 ribbons were prepared by the single roller melt-spinning technique. The microstructure and magnetic properties of directly-quenched and optimally-annealed Nd–Fe–B nanocomposite materials were studied by X-ray diffraction, transmission electron microscopy observations, and magnetization measurements. The experimental results show that crystallizing an precursor into nanocrystallines is ineffective for obtaining better magnetic properties, while nanocomposites with excellent properties can be directly melt spinning at an optimum wheel speed. The microstructure of the ribbons at various distances from the ribbon wheel side was studied. It shows that in the inner part of the ribbons, the directly-quenched ribbons and optimally-annealed ribbons have similar characteristics of microstructure. However, in the free-surface and wheel-contacted surface the grain size of the annealed ribbons is much coarser than that of the directly quenched ribbons.

SPRAY FORMING OF FINEMET ALLOY FE73.5CU1NB3SI13.5B9

Fe -based amorphous alloys are widely used in the magnetic apparatus and generally produced by the single-roller copper-wheel melt spinning method. Spray forming is one of the rapid solidification techniques as the spinning method is, seldom used to fabricate Fe -based amorphous alloys. However in this paper, a Fe -based alloy with the nominal composition of Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ( at .%) alloy was fabricated by spray forming technique with the aim of investigating the formation of amorphous phases and novel microstructures by the high cooling rate involved in this process. The gas/metal mass flow rate used was 0.15, and nitrogen was used as the atomization gas. The resulting deposit and the overspray powder had a median diameter of about 50 μm with a total weight of about 2.2 kg. The microstructure of the deposit was observed by utilizing the X-Ray Diffraction (XRD) and Optical Microscope (OM), as well as Transmission Electron Microscope (TEM), which revealed a heterogeneous varying with the thickness, presenting at center region 15 mm and at border 8 mm with porosities 4 and 9%, respectively. The thicker region showed a fully crystalline microstructure with grain size of about 250nm, whereas the thinner region had a partially amorphous phase with an average grain size of 40nm. The overspray powder was fully crystallized with the grain size of 80nm which was calculated from XRD spectra using the Scherrer formula. The magnetic properties were measured through VSM, giving a poor magnetic saturation value of about 0.3~0.6 T . The coercive force was increased significantly.

Study on the Microstructure and Deformation Behavior of Ultrafine-Crystalline Cu-Y Ribbons

Cu99.8Y0.2, Cu99.2Y0.8 and Cu98Y2 alloy ribbons were prepared by single roller melt spinning. The microstructure was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), high voltage electron microscope (HVEM) and high resolution electron microscopy (HREM). The results showed that α-Cu was the dominative phase in the rapid solidification ribbons of three alloys. A secondary phase Cu4Y was detected in the Cu98Y2 ribbon by XRD. The grain size was in a range of 50-200 nm in the Cu99.2Y0.8 and Cu98Y2 ribbons. Many nano-scale twins and some dislocations existed inside the larger grains. However, the grains in Cu99.8Y0.2 ribbon were in the size of microns and the sub-grains with small misorentations were in 100-200 nm. To understand the deformation mechanism, in situ tensile test were carried out at a High Voltage Electron Microscope (HVEM). The results showed that the deformation is predominated by the dislocation slip in larger grains. To accommodate the deformation, elastic deformation occured in the small grains in the initial stage of the deformation. Meanwhile, some small grains maybe deform by grain rotations. With strain increasing, some fractures generated and propagated along the grain boundaries or across the grains.

Development of Powder Metallurgy Aluminum Alloys with High Strength and High Elevated Temperature Strength

We developed aluminum-based alloys consisting of amorphous, quasicrystalline, nano quasicrystalline plus fcc-Al, nano amorphous plus fcc-Al and glassy phases by a single-roller melt spinning method and a powder-metallurgy processing and examined their structure, thermal, electrical and mechanical properties. The high-pressure gas atomization technique was also used to prepare various aluminum-based alloy powders. Amorphous Al-M-Ni (M: Si, Ge) alloys have good bending ductility and glassy Al-Ln-Ni (Ln: Y, Ce) alloys exhibit a distinct supercooled liquid region. Besides, amorphous or glassy Al-Y-Ni-Co-Sc alloys have the highest strength reported ever before. We also found high strength alloys as Al-Cr-Ce-Co alloys with nano quasicrystalline particles dispersed in fcc-Al phase and Al-M-Fe (M: Ti, V) alloys with nano amorphous particles dispersed in fcc-Al phase. Further, by using the powder metallurgy method, we developed Al-V-Fe and Al-Fe-Cr-Ti alloy rods consisting of quasicrystalline particle dispersed in fcc-Al phase. These aluminum-based alloy rods show high strength, high elevated temperature strength and excellent abrasion resistance.

Study on Preparing and Crystallization Kinetics of Melt-Spun Co-Based Soft Magnetic Amorphous Alloy

Abstract Amorphous ribbons of Co 68.5 Fe 4 Si 10 B 17.5 were prepared by a single roller melt-spinning technique in the air atmosphere. The crystallization products were analyzed by X-ray diffraction. The crystallization kinetics of the alloys were investigated by means of differential scanning calorimetry (DSC) in the mode isothermal annealing. It is found when the isothermal kinetics was modeled by the Johnson–Mehl–Avrami equation, the Avrami exponents are calculated to be in the range of 2.11–2.58 for different isothermal temperatures. This implies that the crystallization of Co 68.5 Fe 4 Si 10 B17.5 amorphous alloy is governed by either diffusion or interface controlled three-dimensional growth, depending on the annealing temperature. On the basis of the Arrhenius relation, the activation energy E c in the isothermal process is calculated to be 113.67 kJ/mol. Finally, details of the nucleation and growth behaviors during the isothermal crystallization are discussed.

Revisiting the glass-forming ability of Ti–Ni–Si ternary alloys

The compositional dependence of glass-forming ability (GFA) was investigated for the Ti–Ni–Si ternary alloys. Glassy ribbons varied with different thicknesses were fabricated via single-roller melt spinning. The optimized glass-forming composition was located at Ti 57Ni 35Si 8, with a critical thickness of about 200 μm for complete glass formation. By characterizing the microstructure of arc-melted ingots of the Ti–Ni–Si ternary alloys, we demonstrate that the glass formation of the Ti 57Ni 35Si 8 alloy correlates with the ( L → Ti 2Ni + TiNi + Ti 5Si 3) ternary eutectic reaction. In addition, the eutectic composition of the ( L → Ti 2Ni + TiNi + Ti 5Si 3) ternary and ( L → TiNi + Ti 5Si 3) pseudo-binary eutectic reaction was determined to be in the vicinity of Ti 63Ni 31Si 6 and Ti 53Ni 37Si 10, with the invariant reaction temperature at 1243 and 1424 K, respectively.

Structure and crystal growth in melt-spun Fe81Ga19 alloys

Abstract Adopting the single roller melt-spinning technique, the Fe81Ga19 ribbons with the thickness of 80 and 25 μm were fabricated at a linear velocity of 5 and 30 m/s, respectively. The microstructural study shows that the ribbons exhibit an initial chill zone on the contact side, leading to columnar growth with an equiaxed zone adjacent to the free side. The formation mechanism of the microstructure is also discussed. The temperature distribution and the cooling rate of the ribbon are calculated in terms of a one-dimensional heat conduction model. When the liquid solidifies, the cooling rate on the free side is estimated to be 3.017×106 and 3.089×107 °C/s for the Fe81Ga19 ribbons with the thickness of 80 and 25 μm, respectively.

Effect of Al substitution for B on magnetic and structural properties of Co-based melt-spun ribbons

This paper reports structural and magnetic properties of rapidly quenched Co 64Fe 4Ni 2B 19− x Si 8Cr 3Al x ( x=0, 1, 2, 3) amorphous ribbons prepared by the single roller melt spinning process. Thermal analysis of the ribbons shows that the replacement of B by Al causes a decrease in the crystallization temperature. Structural studies of the samples have been carried out by transmission electron microscopy and X-ray diffraction. With optimum amount of Al in the alloy, the as-cast material has better soft magnetic properties. The highest maximum permeability (3.55×10 5), saturation magnetization (523.7 mT) and the lowest coercivity (0.8174 A/m) were obtained in the sample with x=2.

Structural and soft magnetic properties of a new nanocrystalline Fe-based and B-free alloy

A new nanocrystalline Fe-based soft magnetic alloy is discussed here. Ingots of nanocrystalline alloys (FeCu)80ZrxSi20−x (x=5, 6, and 8) were prepared by arc melting. The ingots were remelted and cast into 25–30μm thick ribbons by a single roller melt spinning method. X-ray diffraction (XRD) revealed the as-spun ribbons to be amorphous. The structural evolution of these samples was studied by XRD and transmission electron microscopy (TEM) after annealing at 450, 480, and 550°C. XRD shows the primary nanocrystallization product to be the α-Fe(Si) phase. The grain size was observed by TEM to be ∼10nm after annealing at 480°C for 1h and 14nm after 550°C for 1h. ac soft magnetic properties were measured using a Walker AMH 401 ac permeameter. The core loss at an exciting frequency f=100kHz and maximum induction Bm=1kG was determined to be less than 19W∕kg.

Optimal glass-forming composition and its correlation with eutectic reaction in the Ti–Ni–Al ternary system

The composition dependence of glass-forming ability was investigated for the Ti-Ni-Al ternary alloys. Glassy ribbons were fabricated via single-roller melt spinning. The optimal glass-forming composition was located at Ti(54)Ni(32)Al(14), with a critical thickness of about 90 mu m for complete glass formation. With respect to the Ti-Ni binary alloy, Al addition in the system only marginally improves the glass-forming ability. It is attributed to a small atomic size difference between Ti and Al. For the Ti(54)Ni(32)Al(14) alloy, together with the binary eutectic Ti(76)Ni(24) and hypereutectic Ti(68)Ni(32) alloys for comparison, phase selection in the arc-melted ingots was investigated. The optimal glass-forming composition, Ti(54)Ni(32)Al(14), is near the univariant eutectic groove of [L --> Ti(Al)(2)Ni + beta-Ti(Al)] in the phase diagram. It is suggested that if the primary crystallization of the Ti(2)Ni intermetallic can be suppressed, solidification of deeply undercooled melt will undergo such a eutectic reaction prior to glass formation. (C) 2008 Elsevier B.V. All rights reserved.

Crystallization kinetics of (Ni0.75Fe0.25)78Si10B12 amorphous alloy

Amorphous ribbon specimen of (Ni0.75Fe0.25)78Si10B12 has been prepared by a single roller melt-spinning technique in the air atmosphere. The crystallization kinetics of the alloy has been investigated using different thermal analysis by means of continuous heating and isothermal heating. The activation energy of the alloy has been calculated by using Kissinger plot method and Ozawa plot method based on differential thermal analysis data, respectively. The products of crystallization have been analyzed by X-ray diffraction. A single phase of γ-(Fe, Ni) solid solution with grain size of about 10.3 and 18.5nm precipitates in the amorphous matrix after annealing at temperatures 715 and 745K, respectively. The crystallized phases are γ-(Fe, Ni) solid solution, Fe2Si, Ni2Si, Fe3B and unidentified phase after annealing at 765K. The details of nucleation and growth during the isothermal crystallization are expatiated in terms of local Avrami exponent and local activation energy.

Magnetocaloric effect in as‐quenched and annealed Fe91–xYxZr9 (x = 0.5, 10) alloys

AbstractThe magnetization behaviours have been analyzed for as‐quenched and annealed Fe91–xYxZr9 (x = 0, 5, 10) alloys. Samples were prepared by arc melting the high‐purity elemental constituents under argon gas atmosphere and by single roller melt spinning. These alloys were annealed one hour at 500 °C. The magnetic properties of the samples were measured by VSM. The Curie temperature increases with increasing Y concentration (x = 0 to 10). Temperature dependence of the entropy variation ΔSM was found to appear in the vicinity of the Curie temperature. The results show that annealed Fe86Y5Zr9 alloys have a greater magnetocaloric effect than that those in as‐quenched alloys. The value is ‐1.23 J/kg K at ΔH = 1.5 T for annealed alloy and ‐0.89 for as‐quenched alloy, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High-Temperature Internal Friction of Metallic Glasses with Widely Different Glass-Forming Ability

The internal friction (IF) of binary, ternary, quaternary, and quinary metallic glasses with widely different glass-forming ability (GFA) has been studied. A single-roller melt-spinning apparatus was used for preparing ribbon specimens. An inverted torsion pendulum was used in the IF measurement. The measurements were performed from room temperature, through the glass transition temperature, up to the crystallization temperature. The background IF monotonously increases with increasing temperature. The increase is of the thermal-activation type, and the activation energy E is determined. For alloys with higher GFA, the E value tends to be higher. IF is inversely proportional to the measurement frequency. The viscosity relaxation based on the Maxwell model is considered, and the relaxation time τ is determined. A linear relationship is seen between the logarithm of pre-exponential factor τ o and the activation energy E . Explanations of these results and discussions concerned are presented.

Stabilization of metallic glass studied by internal friction measurement

The internal friction Q−1 and the oscillation frequency f of Zr–Ti–Cu–Ni–Be metallic glass specimens were measured using an inverted torsion pendulum with the free decay method. A single-roller melt-spinning apparatus was used for preparing the specimens. Isothermal annealing near the glass transition temperature Tg was performed to investigate the stabilization of the specimens. Q−1 decreased with annealing time t due to the stabilization. Q−1-vs-t was measured at various annealing temperatures Ta, and the values of relaxation time τ for the stabilization process were determined. The dependence of τ on Ta showed that the hydrodynamic behavior represented by the Vogel–Tammann–Fulcher form and the hopping behavior represented by the Arrhenius form were observed in high- and low-temperature regions, respectively. The crossover of the two behaviors was seen at a temperature near and somewhat higher than Tg. The result was discussed on the basis of the viscoelastic relaxation in glassy materials.

Effect of Solidification Conditions on Structure and Properties of Rapidly-Solidified Sn-7.5wt%Sb Alloy

The effect of cooling speed on structure and properties of the rapidly-solidified Sn-7.5wt%Sb has been investigated. The samples in this study were prepared using a single roller melt spinning technique with two speeds: 15.7 and 30.7 m/s, respectively. The results showed formation of the intermetallic compound SnSb. This intermetallic compound changes in the amount which precipitated in the two samples. This behavior tends to affect the properties of these two samples. Also higher cooling speed tends to reduce the crystallite size, which in turn reduces the melting point of the resulting alloy compared to that of the lower cooling speed.

Effect of cooling speed on structure and properties of rapidly solidified Pb–25wt.% Sn alloy

The effect of cooling speed on structure, hardness, mechanical and electrical transport properties of rapidly solidified Pb–25wt.% Sn alloy have been investigated. A single roller melt spinning technique with linear speeds 15.7 and 31.7 m/s, was used for the preparation of specimens. The results showed that a lower cooling speed increased the precipitation of Sn in a Pb-matrix phase as compared with the higher cooling speed. This decomposition behavior decreased the electrical resistivity and increased the internal friction, thermal diffusivity and Vickers microhardness of the lower cooling speed as compared with those of the higher cooling speed.

Effects of heat treatment on the structure and magnetic properties of Al-Ge addedFe73.5−xSi13.5B9Nb3Cualloys

In this work, we have studied the effects of the coaddition of $\mathrm{Al}(1.5\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%)∕\mathrm{Ge}(1\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%)$ and heat-treatment temperature on the structure and magnetic properties of rapidly quenched pure ${\mathrm{Fe}}_{73.5\ensuremath{-}x}{\mathrm{Si}}_{13.5}{\mathrm{B}}_{9}{\mathrm{Nb}}_{3}\mathrm{Cu}$ (FINEMET) alloys prepared by the single roller melt spinning process. Two series of as-spun and heat-treated alloys, 400, 480, 560, 640, and $730\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ for $1\phantom{\rule{0.3em}{0ex}}\mathrm{h}$ in vacuum $({10}^{\ensuremath{-}6}\phantom{\rule{0.3em}{0ex}}\text{Torr})$, were studied using various techniques such as x-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), M\ossbauer spectroscopy, and $B\text{\ensuremath{-}}H$ loop tracer. M\ossbauer analysis carried out on both series of alloys heat treated at $560\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ revealed the presence of two phases, ${\mathrm{Fe}}_{3}\mathrm{Si}$ phase with $D{0}_{3}$ structure and a residual amorphous phase with reduced hyperfine field $(16.9\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ compared to those of $\mathrm{Al}∕\mathrm{Ge}$ added $(22.5\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ and pure FINEMET $(\ensuremath{\sim}23.4\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ alloys, in close agreement with XRD and TEM results. The highest maximum permeability, saturation magnetization, and the lowest coercivity were obtained for both series of alloys when heat treated at $560\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. However, the magnitude of coercivity was lower for the $\mathrm{Al}∕\mathrm{Ge}$ substituted alloy (heat treated at $560\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$) compared to that of the pure FINEMET alloy. This is due to the substitution of Al atoms for Fe as confirmed by our XRD and M\ossbauer results. Further, a higher ferromagnetic amorphous phase Curie temperature $({T}_{C,\mathrm{am}})$ was detected for the $\mathrm{Al}∕\mathrm{Ge}$ added alloy $(322\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ compared to that of the pure FINEMET alloy $(317\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$, which is believed to be mainly related to the presence of Ge atoms in the amorphous matrix. Furthermore, the removal of stress and the setup of nanocrystallization for both series of alloys gave rise to a higher collinear magnetic moment angle. However, this was not the case for the samples heat treated at temperatures above $560\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, for which the formation of the Fe-B hard magnetic phase was confirmed by our XRD, TEM, and M\ossbauer results. Finally, the structural-magnetic properties relationship is discussed for various samples studied in this work.

Crossing and detwinning of fully twinned martensites in rapidly solidified CoNiGa alloy ribbons

Microstructures and martensitic transformation behavior have been examined as for CoNiGa ferromagnetic shape memory alloy (FMSMA) ribbons rapidly solidified by a single-roll melt spinning. Transmission electron microscopy (TEM) bright-field images revealed dense striations in the martensite variants. These striations are identified to be thin twins, as in other FMSMAs. The analysis of a pair of Kikuchi lines in a selected-area electron diffraction pattern indicates that the b/ a and c/ a axial ratios of the orthorhombic martensite are 1.01 and 0.961, respectively. Crossings of fully twinned martensite variants are frequently observed in the TEM bright-field images, and the internal twins disappear in the crossing regions, that is, the regions are subjected to detwinning. In addition to the crossing of martensite variants, checkers and straight bands of martensite variants are observed in the crystal grains of the ribbon surface. These typical morphologies are supposed to be caused by some self-accommodation of martensitic transformation stress.

Formation and mechanical properties of ductile Fe-based amorphous alloys using a cast iron with minor addition of B and Al

Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT 1-xB x) 99Al 1 ( x is from 0.006wt% to 0.01wt%) amorphous alloys exhibit onset crystallization temperatures and Curie temperatures of 759–780 and 629–642 K respectively, and which increase with B content. The amorphous ribbons are ductile and can be bent 180° without breaking. With the increase in B content from 0.006wt% to 0.01wt%, the Vickers microhardness of the amorphous alloys increases from Hv 830 to Hv 1110. The effects of the additional B and Al elements on the glass forming ability and mechanical properties were also discussed.

In situ X-ray diffraction investigation of nanocrystallization of amorphous Co–Fe–Zr–B alloys

Cobalt-rich soft-magnetic alloys were recently developed as amorphous materials with promising engineering properties, e.g. high mechanical strength, excellent magnetic properties and high corrosion resistance. The crystallization of the as-prepared amorphous alloys plays a crucial role in most technological applications of these advanced soft-magnetic nanomaterials. Amorphous ribbons with nominal composition Co 56Fe 16Zr 8B 20 (at%) were here obtained by single-roller melt spinning. The nucleation and growth of nanoscale phases during constant-rate heating of as-quenched and of high-energy ball-milled Co-rich amorphous soft-magnetic alloys were investigated by differential scanning calorimetry and by in situ high-temperature powder X-ray diffraction using synchrotron radiation. The temperature/time evolution of the crystallite size and of average microstrain was obtained from the X-ray diffraction line-profile analysis (LPA) of the powder diffraction patterns.