Melt-spun Alloys Research Articles

Compositional dependence of glass-forming ability, mechanical and magnetic properties of Ce-Ni-Al (Ga) alloys

The glass-forming ability, mechanical and magnetic properties of Ce60Ni25Al15-xGax (x=0, 4, 8 and 15) melt-spun alloys have been investigated. All the alloys show the formation of glassy phase. The supercooled liquid region increases with increase in Ga addition and becomes maximum for x=15 indicating its better glass-forming ability for this composition. A new metallic glass (MG) composition Ce60Ni25Ga15 has been found upon complete substitution of Al by Ga. The mechanical behavior of these alloys has been studied by determining various indentation parameters such as micro-hardness, yield strength and Meyer’s exponent. The microhardness property of the Ce-Ni-Al alloy is improved by the addition of Ga. The difference in the formation of shear bands for x=0 and 15 alloys are discussed by estimating the pile-up parameter. The magnetization (M-H) curves of all the samples at 5 K show paramagnetic characteristics with no magnetic hysteresis. The findings reveal that the concentration of Ga has a significant impact on the properties of these alloys.

Plastic quasicrystal-containing alloys prepared by annealing pseudo-high entropy Zr70–75(Al, Ni, Cu, Ag)25–30 glassy alloys

A glassy (G) phase was formed for Zr-rich Zr70–75(Al, Ni, Cu, Ag)25–30 (atomic percent, at.%) melt-spun alloy ribbons. These glassy alloys exhibit the glass transition, followed by a supercooled liquid region and then three-stage crystallization. The glass transition temperature and the onset temperature for the first-stage crystallization (Tx1) decrease from 630 to 668 K, respectively for the 70Zr alloy to 619 and 652 K, respectively for the 75Zr alloy. The first-stage exothermic peak is due to the precipitation of an icosahedral quasicrystal (IQ) phase. The IQ particle size decreases from 10 nm to 6 nm with increasing Zr content from 70at.% to 74at.%. The [G + IQ] phases change to Zr2Ni + Zr2(Cu, Ag) phases after the second exothermic peak and then Zr2Ni + Zr2(Cu, Ag) + Zr5Al3 phases after the third stage. It is noticed that the as-spun glassy alloy ribbons as well as the annealed [G + IQ] phase ribbons exhibit good bending plasticity. Furthermore, the 70Zr thicker ribbons also exhibit high tensile fracture strength of 1090–1187 MPa and plastic elongation of 0.17 %–0.42 %. The fracture mode is similar to that of ordinary bulk metallic glasses. The Vickers hardness (Hv) is 480 for 70Zr alloy and decreases to 436 for 75Zr alloy. The precipitation of IQ phase causes a significant increase in Hv to about 554. The formations of glassy alloys with high Zr contents of 70at.%–75at.% by melt spinning as well as the [G + IQ] phase alloys with good bending plasticity by annealing hold promise for the creation of a new type of engineering material, transcending mere academic novelty.

Enhanced thermoelectric properties of p-type α-SrSi2 nanostructured by melt spinning

A melt spinning technique followed by spark plasma sintering technique was used to synthesize nanostructured SrSi2 alloys with high homogeneity and density (>99 %). The impact of the wheel speed on the microstructure of the ribbons was investigated and shows the presence of nanostructures. After sintering, typical grain size between ∼140 and ∼400 nm was obtained. We show that they permit to decrease strongly the lattice thermal conductivity. The ZT values of these melt-spun alloys are about two times higher than in our bulk material. We finally show that this short step process could be of strong interest for further development.

The effect of Mn on structural, magnetic and magnetoresistance properties of Ni–Mn–Sb Heusler melt spun ribbons under extreme conditions

Ni50 − x Mn37 + x Sb13 (NMS (x = 4–6)) melt-spun Heusler ribbon was fabricated by employing the arc melting technique. Also, the electrical, structural, and magnetic characteristics of melt-spun alloy ribbons with chemically increased Mn (a decrease in Ni concentration) content are also being investigated. Further, it has been noticed that, the Curie temperatures of the austenitic (T C A) phase and the martensitic phase transition temperature (T M) are both shifted toward higher temperatures, by increasing the amount of Mn under 500 Oe (0.05 T) of applied magnetic fields. The discontinuity of field cooling (FC) and zero field cooling (ZFC) curves reveals the irreversibility of magnetization caused by inhomogeneous magnetic anisotropy lower the exchange bias (EB) (blocking bias) temperature. Furthermore, the disappearance of exchange bias (EB) in ribbon alloys with increasing temperature is supported by the fact that coercivity (H C) gradually increases with temperature and increases at 40 K, and then decreases with temperature. Additionally, a −ΔS Max of −5.21 Jkg−1·K−1 for a ribbon with x = 6 is acquired at 312 K with a 50 kOe (5 T) change in the applied magnetic field. Increases in Mn content result in −ΔS M values in NMS alloy ribbons of −4.3, −4.7, and −5.2 Jkg−1·K−1 and the same trend is observed in negative magneto-resistance ((−MR) (%)) values of −9%, −11%, and −14% for x = 4–6, respectively. Here, the super zone boundary that is close to the Fermi surface is responsible for the change in −MR.

Shape memory and elastocaloric properties of melt-spun NiMn-based Heusler alloys

In the present work, towards further development of NiMn-based Heusler-type elastocaloric alloys a series of melt-spun ribbons have been prepared from three multicomponent Ni-Mn-Sn-based metamagnetic shape memory alloys (MetaMSMAs) and two multicomponent Ni-Mn-Ga-based ferromagnetic shape memory alloys (FSMAs). Their thermoelastic martensitic transformation (TMT), crystal structure and thermomechanical properties have been studied in detail. Whereas FSMAs ribbons showed a conventional stress-strain behavior at TMT and conventional elastocaloric effect (eCE), MetaMSMAs ribbons, in turn, exhibited highly pronounced inverse stress-strain and inverse eCE characteristics at TMT. The abnormal thermomechanical behavior of the MetaMSMA ribbons is produced by the presence of significant internal stresses due to appropriate amount of quenched-in defects resulting from the rapid solidification of melt-spun alloys. The results of the present study can serve as a guide for the design of new eCE-efficient materials in the form of ribbon.

Electrochemical Hydrogen Storage Kinetics and Microstructure of the Rapidly Quenched Alloy Mg2Ni0.75Zn0.25

The Mg2Ni0.75Zn0.25 alloys are prepared from Mg2Ni as master alloy and pure Zinc ingot by remelting process in this work. The microstructures, electrochemical properties and desorption kinetics of the as-cast and melt-spun alloys are investigated. The phase compositions and microstructures of the alloys are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). The results show that the segregation atoms rich in Zn can inhibit the growth of Mg2Ni grains, especially the nanocrystalline grains formed in Mg2Ni0.75Zn0.25 alloy after melt-spinning process. The rapidly quenched Mg2Ni0.75Zn0.25 alloy exhibits the largest discharge performance (102.1 mAh g−1) and dehydrogenation activation energy (14.68 kJ mol−1). The improvement of the kinetic properties is related to the hydrogen diffusion rate (D) in the alloys and the charge transfer reaction on the surface. The rapidly quenched Mg2Ni0.75Zn0.25 alloy has the largest D, 6.187 × 10−11 cm2 s−1. The doping of Zn aggravates the corrosion of alloy electrodes, which destroys the oxide layer on the alloy surface, provides a channel for the diffusion of hydrogen atoms.

Magnetoelastic transition and negative thermal expansion of Fe2Hf0.83Ta0.17 ribbons

In this work, the magnetocaloric effect and negative thermal expansion in melt-spun Fe2Hf0.83Ta0.17 Laves phase alloys were studied. Compared to arc-melted alloys, which undergo a first-order magnetoelastic transition from the ferromagnetic to the antiferromagnetic phase, melt-spun alloys exhibit a second-order transition. For Fe2Hf0.83Ta0.17 ribbons, we observed a large volumetric coefficient of negative thermal expansion of −19 × 10−6 K−1 over a wide temperature range of 197 – 297 K and a moderate adiabatic temperature change of 0.7 K at 290 K for a magnetic field change of 1.5 T. The magnetic field dependence of the transition temperature (dTt/dµ0H = 4.4 K/T) for the melt-spun alloy is about half that of the arc-melted alloy (8.6 K/T). The origin of second-order phase transition of the melt-spun alloy is attributed to the partially suppressed frustration effect, which is due to the atomic disorder introduced by the rapid solidification.

The microstructure and thermal stability of the two-phase amorphous melt-spun alloys ejected from a double chamber crucible.

This work presents the microstructure and properties of two-phase amorphous melt-spun alloys ejected from the crucible with partition between liquids. The microstructure was studied by scanning electron microscopy and transmission electron microscopy and the phase composition was studied by X-ray diffraction. The thermal stability of the alloys was determined using differential scanning calorimetry. The microstructure study proves that the composite alloys are heterogeneous because of the existence of the two amorphous phases obtained due to the use of a partition between the liquids. This microstructure correlates with complex thermal characteristics not found in homogeneous alloys of the same nominal composition. The layered structure of these composites influences the formation of fractures during tensile tests. This article is protected by copyright. All rights reserved.

Enhancement of hydrogen storage properties from amorphous Mg85Ni5Y10 alloy

Amorphous precursors have been successfully used in the preparation of Mg-based hydrogen storage materials. Unfortunately, the improvement and the underlying mechanisms of hydrogen storage kinetics of these materials are far from being fully understood. Herein, the hydrogen storage properties of amorphous and crystalline Mg85Ni5Y10 (at%) alloys prepared by melt-spinning and induction-melting, respectively, were comparatively studied. The results indicate that the hydrogen storage capacity and hydrogen release/uptake kinetics of the melt-spun alloy are much higher and faster than that of the induction-melted alloy. The reversible storage capacity of 4.2 wt% H2 for the activated melt-spun Mg85Ni5Y10 alloy is much higher than 3.8 wt% for the induction-melted sample at 200 °C. Moreover, the melt-spun alloy could release 4.1 wt% within 30 min at temperatures above 275 °C, which is close to its theoretical hydrogen storage capacity of 4.2 wt%, while the induction-melted alloy could only release 3.5 wt% H2 under the same conditions. Multiple cracks formed during the activation cycles together with a uniform distribution of catalytic YH2/YH3 and Mg2Ni/Mg2NiH4 particles are thought to be responsible for the excellent hydrogen storage kinetics of the melt-spun alloy. This work provides guidance for further designing and developing high-performance and non-crystalline Mg-based hydrogen storage materials.

Microstructure and catalytic properties of rapidly solidified Al-28.5 at% Fe and Al-28.5 at% Co alloys applied for selective hydrogenation of phenylacetylene

The Al 71.5 Fe 28.5 and Al 71.5 Co 28.5 (at.%) melt-spun alloys were examined in terms of microstructure evolution and catalytic response in the semihydrogenation reaction of phenylacetylene to styrene. In the as-spun state ribbons showed a single-phase composition. The Al 71.5 Co 28.5 alloy contained columnar grains of a metastable decagonal quasicrystal, which transformed into hexagonal Al 5 Co 2 and monoclinic Al 3 Co phases after heat treatment at 900 °C. The Al 71.5 Fe 28.5 ribbon had an ordered orthorhombic Al 5 Fe 2 phase structure in both the as-spun and annealed states. The pulverized ribbons revealed considerable catalytic activity for selective hydrogenation of phenylacetylene to styrene. The best results were achieved for the as-spun quasicrystalline Al 71.5 Co 28.5 alloy, showing a conversion rate of above 80% after 2 h reaction time. The selectivity to styrene was 60% for all catalysts. The tested powders retained their phase composition following liquid reaction therefore the proposed materials can be considered for catalytic use. • The Al5Co2 and Al5Fe2 ribbons were prepare by melt spinning methods • Decagonal quasicrystal in the Al5Co2 transforms into Al 5 Co 2 and Al 3 Co after annealing • Ordered orthorhombic Al 5 Fe 2 phase in both the as-spun and the annealed Al5Fe2 ribbons • Catalytic activity of the powdered ribbons in hydrogenation of phenylacetylene • The conversion rate exceeds 80% after 2 h reaction time for quasicrystalline Al5Co2

The effect of stress-annealing on the mechanical and magnetic properties of several Fe-based metal-amorphous nano-composite soft magnetic alloys

Fe-based metal-amorphous nanocomposites (MANCs) are the subject of many contemporary studies for their unique tunable soft-magnetic properties. The alloys can exhibit some of the smallest losses and highest power storage capabilities of available materials used in electromagnetic inductors. Here, the magnetic and mechanical properties of Fe72.5Nb2Mo2Cu1Si15.5B7 at.%, Fe68.5Co5Ta3Cu1Si16.5B6 at.%, Fe68.5Co5Ta3Cu1Si16B6.5 at.%, and Fe73.5Ta3Cu1Si16B6.5 at.% melt-spun alloys were investigated in relation to their ability to be stress-annealed to tune permeability while simultaneously minimizing losses in tape-wound inductor cores. Mechanical and physical properties of the as-cast and processed ribbons including relaxation and crystallization temperatures and failure strains were measured using thermomechanical analysis (TMA), uniaxial tension, and bend tests to help inform the stress-annealing parameters. Magnetic properties were measured for the as-cast and stress-annealed materials in both wound-cores and flat ribbon strips. The alloys exhibited severe embrittlement during heating, thus creating significant challenges when tuning magnetic properties with an in-line stress-annealing (SA) process. However, when conditions were optimized, core losses as low as 1.14 W·kg−1 were obtained when cores were excited at 10 kHz to a maximum induction field of 0.1 T, which are among the lowest reported in the literature. Based on this preliminary effort, understanding of the stress state in amorphous precursor ribbons prior to SA could reveal the key to developing more robust in-line SA processes for brittle Fe-based MANCs.

Comparison of Oliver-Pharr and Work of Indentation Approach to Determine the Mechanical Properties of Melt-Spun Al-12%Wt.Si-0.5%Sb Alloy

In this research, the hardness and reduced modulus of Al-%wt.12-%wt.0.5Sb melt-spun alloy were evaluated by using depth sensing indentation and atomic force microscopy techniques. We considered two approaches, Oliver-Pharr and Work of Indentation, to analyse the load-displacement curves. The ratio of final depth to maximum depth was found to be higher than the reported critical value of 0.70, which mean that pile-up was dominant in the melt-spun. A pile-up around the deformed surface was observed from atomic force microscope, which is consistent with the aferomentioned result. The hardness calculated by Oliver-Pharr method was higher than that calculated by Work of Indentation Approach. According to the results, Work of Indentation Approach was more reliable than the Oliver-Pharr approach because of reducing pile-up affect.

Effects of Sb and/or Sn concentrations on the SbSn formation in a ternary melt-spun Pb–Sb–Sn alloy

The Pb–Sb–Sn alloy still considered a mandatory choice in the production of the metallic grids in lead-acid batteries. This work aims to study the effects of the commutative concentration of Sb and Sn on the formation of SbSn IMC in ternary melt-spun Pb–Sb–Sn alloy, as well as the effects of initiated on its structural, mechanical and electrical properties. X-ray diffractions (XRD), Dynamic resonance technique, Vickers hardness tester, and High Precision Micro-ohmmeter were used to investigate the melt-spun Pb–Sb–Sn alloys. The results showed that a balanced Sb–Sn content in the melt-spun Pb80–Sb10–Sn10 alloy results in a high concentration of refined SbSn and small particle sizes for α-Pb and SbSn (44.37 and 20.13 nm respectively), low lattice distortion (4.56 × 10−4), low cell volume (120.993 (Å)3), and the highest density (9.232 g/cm3) compared to that of the other melt-spun alloys. Mechanical improvements in terms of room-temperature dynamic Young's modulus (20.8 GPa), bulk modulus (42.3 GPa), shear modulus (7.2 GPa), and Vickers micro-hardness (115.706 MPa) have been revealed, which are strongly related to structural changes. The refined and high concentration of SbSn is responsible for its improved electrical conduction and electrical stability at elevated temperatures (its electrical performance). The aforementioned characteristics suggest that melt-spun alloy is more reliable for use in harsh environments, such as under the hood of a vehicle.

Influence of preparation methods on the hydrogen absorption properties of Zr7V5Fe getter alloy

Zr-V-Fe alloys are promising getter materials due to their remarkable hydrogen storage properties. In this work, the effects of preparation methods including annealing, melt-spinning, and melt-spinning & annealing on the microstructure as well as the activation properties and hydrogen absorption properties of Zr7V5Fe alloy are systematically investigated. Phase structure investigations show that annealed alloys have the largest cell volume of the main hydrogen-absorbing phase ZrV2. Compared to annealed alloys, the cell volume of α-Zr phase and ZrV2 phase is smaller in melt-spun alloys. As for the melt-spun & annealed alloy, the cell volume of ZrV2 phase decreases and the cell volume of α-Zr phase increases after annealing. And the PCT curves show that with the cell volume of the ZrV2 phase increasing, the plateau pressure decreases while the hydrogenation capacity increase accordingly. As a result, the annealed alloy has the lowest plateau pressure about 0.02 Pa and the highest hydrogenation capacity about 1.4 wt% at 623 K. The kinetic curves illustrate that the hydrogen absorption process is diffusion-controlled for all of the alloys. The melt-spun & annealed alloy has the best hydrogen absorption kinetic performance because it has a well homogeneous distribution of α-Zr phase after melt-spinning and annealing treatment. Melt-spun as well as melt-spun & annealed alloys have no incubation period and exhibit superior activation properties compared to annealed alloys. This is due to the higher content of Zr elements and thinner passivation layer on the surface of melt-spun and melt-spun & annealed alloys than that of annealed alloy.

Magnetic softening of the Fe83Si3B11P2Cu1 amorphous/nanocrystalline alloys with large-size pre-existing α-Fe grains by high heating-rate annealing

The microstructure and soft magnetic properties of Fe83Si3B11P2Cu1 (at.%) nanocrystalline ribbons with different thicknesses up to 40 μm obtained by annealing the amorphous/nanocrystalline precursors at various heating rates (HRs) were studied. It was found that the thicker melt-spun alloy ribbons contain more and coarser α-Fe grains owing to the lower cooling rates during the solidification of melt spinning. By rapidly annealing the relatively thick amorphous/nanocrystalline precursors with the large-size pre-existing α-Fe grains at a high HR of about 100 °C/s, the resultant nanocrystalline alloys exhibit low coercivity (Hc) of about 5.2 A/m and high saturation magnetization (Bs) of about 1.83 T, which are approximate to the nanocrystalline alloys acquired by annealing the precursors with an amorphous structure. The strong competition among the formation of primary nuclei and the growth of the pre-existing and the newly-nucleated α-Fe induced by the more rapid annealing could effectively suppress the coarsening of the pre-existing α-Fe with the large size up to about 30 nm, which facilitates the formation of the fine and uniform nanostructure and magnetic softening of the resultant nanocrystalline alloys.

The Influence of Boron on Microstructural Evolution, Mechanical and Magnetic Behavior of Amorphous Fe91−x(Zr5-Nb4)Bx Melt-Spun Alloys

In this work, we report a systematic study on the microstructure evolution of rapid solidified Fe91−xZr5Nb4Bx alloys (x = 10, 15, 20, 25, 30 at%) under melt-spinning conditions. Mechanical and magnetic properties are also evaluated. X-ray diffraction patterns indicate that the microstructure across the compositional series consists of an amorphous matrix with partial crystallization when boron concentration is increased. These features were identified by transmission electron microscopy (TEM). The radial distribution function (RDF) affords to resolve the nearest-neighbor configuration. The tensile and microhardness properties were measured to correlate the microstructural evolution with boron content. On the other hand, the magnetic properties of these alloy series were determined by vibrating sample magnetometry (VSM); the saturation magnetization and Curie temperature showed an increasing tendency when increasing the boron content, reaching values up to 110 Am2kg−1 and 465 K, respectively. In addition to the aforementioned, the coercive field remained constant. All these magnetic properties were correlated with the microstructure features observed by XRD, RDF and TEM.

Hydrogen storage performance of LaNi3.95Al0.75Co0.3 alloy with different preparation methods

Rare-earth AB5-type La–Ni–Al hydrogen storage alloys are widely studied due to their extensive application potentials in hydrogen isotope storage, hydrogen isotope isolation and hydrogen compressors, etc. Good hydriding/dehydriding kinetics, easily activation, high reversibility are important factors for their practical application. However, their overall hydrogen storage performance, especially plateau pressure and hydrogen absorption/desorption durability need to be further optimized. In this study, the microstructures and the hydrogen storage properties of as-cast, annealed, and melt-spun LaNi3.95Al0.75Co0.3 alloys were investigated. The experimental results of XRD and SEM showed that all alloys contained a pure CaCu5 type hexagonal structure LaNi4Al phase. The cell volume increased in an order of annealed ​> ​melt-spun ​> ​as-cast, resulting in a lower hydrogen absorption/desorption plateau pressure and a more stable hydride phase. The hydrogen storage capacity of three alloys was almost the same. The slope factor of the annealed and melt-spun alloys is smaller than the as-cast alloy, indicating that heat-treatment process can make the alloys more uniform. For the cycle stability of the alloys, the hydrogen absorption rate of the annealed alloy and melt-spun alloy was much faster than that of the as-cast alloy after 500 cycles. The melt-spun alloy showed high pulverization resistance during hydrogen absorption/desorption, and exhibited an excellent cycling retention of 99% after 500 cycles, suggesting that melt-spinning process can enhance the cycle stability and improve the cycle life of the alloy.

Oxide Formation in a Melt Spun Alloy in the Zr-Ni-Cu System

The microstructure of a melt-spun Zr28Ni44Cu28 (at. %) alloy was characterized in order to determine the structures and compositions of the crystalline phases that compete with glass formation during rapid solidification. Two crystalline phases were identified, namely, a face centered cubic (FCC) zirconium oxide phase and a primitive cubic version of the big-cube oxide phase, using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy techniques. Our results indicate that the Zr-O atomic pair interaction is preferential compared to the other atomic pair possibilities, supporting the formation of Zr-based oxides over the equilibrium phases in the ternary Zr-Ni-Cu system. Further, the results provide insight into the mechanisms of oxygen-induced crystallization in Zr-based BMGs and the corresponding decrease in glass forming ability (GFA) with increasing oxygen concentrations.

Tunning Ce valence and optimizing intergranular phase to prepare high abundance (La, Ce, Pr)-Fe-B permanent alloys with excellent properties

The regulation of Ce valence and the optimization of intergranular phase can effectively improve magnetic properties, which is beneficial in promoting the application of high abundance rare earth in permanent magnets. In this work, [(La0.3Ce0.7)xPr1-x]17Fe78B6 (x = 0.1–0.7) melt-spun alloys are prepared. The results illustrate that, Ce shows the mixed valency consisting of Ce3+ and Ce4+ configuration, and when x = 0.3, the alloy possesses the highest Ce3+ ratio. Meanwhile, the highest Ce4+ ratio can be determined in x = 0.1 alloy. TEM characterization demonstrates that, the intergranular rare earth oxides including CeO2 phase, Pr2O3 phase, (Pr, Ce)2O3 as well as La2O3 phase can be determined, among which CeO2 phase, existed in x = 0.3 alloy, is more beneficial in elevating the coercivity. Thus, the optimum comprehensive magnetic properties with the remanence of 6.5 kG and the coercivity of 14.9 kOe can be obtained in x = 0.3 alloy. In addition, due to more uniform microstructure of melt-spun alloy with x = 0.3, higher thermal stability can be obtained. Elemental metallurgical behavior reveals that La, Ce and Pr elements are enriched in intergranular phase, and main phase region is rich for Fe element.

Effects of La on Thermal Stability, Phase Formation and Magnetic Properties of Fe–Co–Ni–Si–B–La High Entropy Alloys

The microstructure, phase formation, thermal stability and soft magnetic properties of melt-spun high entropy alloys (HEAs) Fe27Co27Ni27Si10−xB9Lax with various La substitutions for Si (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) were investigated in this work. The Fe27Co27Ni27Si10−xB9La0.6 alloy shows superior soft magnetic properties with low coercivity Hc of ~7.1 A/m and high saturation magnetization Bs of 1.07 T. The content of La has an important effect on the primary crystallization temperature (Tx1) and the secondary crystallization temperature (Tx2) of the alloys. After annealing at relatively low temperature, the saturation magnetization of the alloy increases and the microstructure with a small amount of body-centered cubic (BCC) phase embedded in amorphous matrix is observed. Increasing the annealing temperature reduces the magnetization due to the transformation of BCC phase into face-centered cubic (FCC) phase.