Single Roller Melt Spinning Research Articles

The enhanced mechanical properties in rapid solidification technology al alloy

Abstract As one of the most important alloys of Al-Mg-Si series aluminum alloys, 5083 aluminum alloy is widely used in mechanical parts, structural engineering, modern construction, transportation, and other fields. The objective of the present study is to explore the feasibility of producing 5083 Al alloy ribbons with increased mechanical properties via rapid solidification technology, namely single-roll melt spinning. Metallography, X-ray diffraction, hardness, and tensile tests are used to study and compare the microstructure and mechanical properties of aluminum alloy hot extruded rods and explore the different extrusion temperatures of aluminum alloy. Our results show that the hot-extrusion process (300°C, 350°C, 400°C) is used to process the ultra-fine grain ribbon into bars that can be applied to structural parts. The 5083 alloy bar obtains the best mechanical properties under the 350°C extrusion process, in which the tensile strength is up to 678 MPa and the hardness reaches 118 HV.

Influence of Al addition on the microstructure and properties of Fe25Co25Ni25(Si0.3B0.7)25 high entropy metallic glass

This research work was focused on the development of a new series of high entropy metallic glasses (HE-MGs) combined with higher thermal stability, acceptable soft magnetic property, microhardness and good corrosion resistance by adding various Al content (1–8 at.%) on the basis of Fe25Co25Ni25(Si0·3B0.7)25 high entropy metallic glass using single-roller melt-spinning approach. It is found that the proper addition of Al can efficiently improve the anti-corrosion performance of high entropy metallic glasses, in particular, the corrosion current density is decreased from 7.61 μA/cm2 and 9.26 μA/cm2 for the 1 at.% and 2 at.% Al-added alloys to 5.11 μA/cm2 for the 5 at.% Al-added alloy. However, the improvement of Al content could deteriorate the soft magnetic property and thermal stability of HE-MGs. The saturation magnetization flux density and onset crystallization temperature reduce from 0.85 T to 766.15 K for the 1 at.% Al-added alloy to 0.53 T and 736.75 K for the 8 at.% Al-added alloy. Besides, the Vickers’ microhardness of all investigated alloy ribbons can reach 1124 HV0.2 or above. Therefore, this kind of senary new-type HE-MGs can be used as a promising magnetic shielding metal material with high hardness, superior thermal stability and good anti-corrosion performance for the surface protection of key component in harsh marine corrosive environment.

Pulsed laser-indued nanoscale phase transition in FePC alloy with enhancing the catalytic activity in dye wastewater degradation

A nanoscale heterogeneous environmental catalyst, FePC alloy, was successfully fabricated by a single-roller melt spinning technique. The prepared catalyst had a biphasic disorder structure with α-Fe nanocrystallites embedded in the amorphous matrix. The pulsed laser process effectively improved the nanoscale heterogeneity degree, thermodynamic properties, surface photothermal conversion, corrosion resistance and hydrophilicity of the catalyst. The 60 W pulsed laser processing induced the nanocrystalline Fe3P precipation in the catalyst, which is transformed from α-Fe and amorphous matrix, promoting the electron donation rate of the galvanic cell system; therefore, the 60 W pulsed laser processed catalyst exhibited an excellent catalytic performance, such as a high k value, strong TOC removal rate and low activation energy. In addition, compared with other oxide, metallic crystal and metallic glass catalysts, this catalyst exhibited a much higher surface area-normalized rate constant kSA. The reusability test showed that this catalyst exhibited a reliable stability, and its decolorization efficiency at the 20th cycle still remained above 95 %; moreover, the parameter analysis showed that it had a strong adaptability in the persulfate system. This study provides a new strategy for designing and fabricating the efficient, low-cost and environmental catalysts for dye wastewater degradation.

Anticorrosion and Antimicrobial Tannic Acid-Functionalized Ti-Metallic Glass Ribbons for Dental Abutment.

In this study, a recently reported Ti-based metallic glass (MG), without any toxic element, but with a significant amount of metalloid (Si-Ge-B, 18 atom %) and minor soft element (Sn, 2 atom %), was produced in ribbon form using conventional single-roller melt-spinning. The produced Ti60Zr20Si8Ge7B3Sn2 ribbons were investigated by differential scanning calorimetry and X-ray diffraction to confirm their amorphous structure, and their corrosion properties were further investigated by open-circuit potential and cyclic polarization tests. The ribbon's surface was functionalized by tannic acid, a natural plant-based polyphenol, to enhance its performance in terms of corrosion prevention and antimicrobial efficacy. These properties can potentially be exploited in the premucosal parts of dental implants (abutments). The Folin and Ciocalteu test was used for the quantification of tannic acid (TA) grafted on the ribbon surface and of its redox activity. Fluorescent microscopy and ζ-potential measurements were used to confirm the presence of TA on the surfaces of the ribbons. The cytocompatibility evaluation (indirect and direct) of TA-functionalized Ti60Zr20Si8Ge7B3Sn2 MG ribbons toward primary human gingival fibroblast demonstrated that no significant differences in cell viability were detected between the functionalized and as-produced (control) MG ribbons. Finally, the antibacterial investigation of TA-functionalized samples against Staphylococcus aureus demonstrated the specimens' antimicrobial properties, shown by scanning electron microscopy images after 24 h, presenting a few single colonies remaining on their surfaces. The thickness of bacterial aggregations (biofilm-like) that were formed on the surface of the as-produced samples reduced from 3.5 to 1.5 μm.

Toxic element-free Ti-based metallic glass ribbons with precious metal additions

We introduce four new biocompatible toxic element-free Ti-based metallic glass (MG) compositions with constant metalloid (Si10B5) and varying precious metal (PM) contents for simultaneous improvement in glass-forming ability (GFA) and corrosion properties. Being completely free from cytotoxic elements like Cu, Ni, or Be, which are indispensable for Ti-based bulk metallic glass production, limits the GFA of the studied alloys significantly. However, avoiding these elements also realizes an unprecedented corrosion resistance in simulated body fluids, which supports the potential utilization of the alloys as long-lasting dental implant material. The novel Ti60Zr15Si10B5Pd10, Ti60Zr15Si10B5Pt10, Ti60Zr15Si10B5Pd5Pt5, Ti60Zr15Si10B5Pd5Au5 alloys are obtained in ribbon form using conventional single-roller melt spinning. The effect of the PM additions on the GFA and corrosion resistance of the alloys is investigated comparatively with each other by synchrotron X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and cyclic polarization tests. Further, their Vickers hardness values are deduced using an ultra-sensitive micro indentation method, and the findings are discussed based on the composition dependence. It was found that the Ti60Zr15Si10B5Pd5Pt5 alloy presents a promising GFA while showing outstanding corrosion resistance in a simulated body fluid at 310 K.

Effects of adding B element on amorphous forming ability, magnetic properties, and mechanical properties of FePBCCu alloy

Fe-based amorphous alloys are widely used in power electronics fields such as transformers and reactors due to their low coercivity, high permeability and low loss. However, the relatively low saturation magnetization (<i>B</i><sub>s</sub>) limits their further applications. Generally speaking, the adjustable magnetic Fe content as an effective strategy can ameliorate the magnetic properties, and the higher the Fe content, the higher the obtained <i>B</i><sub>s</sub> is, but the decrease of the corresponding non-magnetic element content will result in the drop of the ability of alloys to form amorphous phase, leading to the deterioration of the magnetic softness and bending ductility of nanocrystalline alloys. To address this critical issue, in this work, based on the metal-metalloid hybridization, the FePBCCu amorphous ribbons, each with a thickness of ~25 μm, are prepared by the single-roller melt spinning method via 7% (atomic percent) B substitution for P, and the effects of B element addition on the ability to form amorphous phase, magnetic properties and mechanical properties of ribbons are investigated. Thermodynamic behavior shows that the addition of small quantities of B element can reduce the structural heterogeneity of alloy and the crystallization driving force as well, thus effectively improving the thermal stability of the amorphous matrix. The melting and solidification curves show that the addition of B can promote alloy to approach to the eutectic composition, and there is a large degree of undercooling. As a result, the critical thickness of ribbons increases from ~21 μm for B-free alloy to ~30 μm for B-added alloy due to the micro-alloying effect. The addition of B increases the effective magnetic moment of magnetic atoms in alloy, resulting in the increase of the saturation magnetization. Furthermore, the results of nanoindentation tests show that the modulus value of the B-added alloy decreases greatlyr and fluctuates in a smaller range than that of the B-free alloy, which is closely associated with the structural uniformity of the alloy.

Corrosion and in vitro cytocompatibility investigation on the designed Mg-Zn-Ag metallic glasses for biomedical application

In the present work, seven Mg-Zn-Ag alloys with the nominal composition of Mg96-xZnxAg4 (x = 17, 20, 23, 26, 29, 32, 35 in at.%) were prepared by induction melting and single-roller melt-spinning. The X-ray diffraction (XRD) analyses indicate the metallic glasses with three composition of Mg73Zn23Ag4, Mg70Zn26Ag4, and Mg67Zn29Ag4 were obtained successfully. The differential scanning calorimetry (DSC) measurement was used to obtain the characteristic temperature of Mg-Zn-Ag metallic glasses for the glass-forming ability analysis. The maximum glass transition temperature (Trg) was found to be 0.525 with a composition close to Mg67Zn29Ag4, which results in the best glass-forming ability. Moreover, the immersion test in simulated body fluid (SBF) demonstrate the relative homogeneous corrosion behavior of the Mg-Zn-Ag metallic glasses. The corrosion rate of Mg-Zn-Ag metallic glasses in SBF solution decreases with the increase of Zn content. The sample Mg67Zn29Ag4 has the lowest corrosion rate of 0.19 mm/yr, which could meet the clinical application requirement well. The in vitro cell experiments show that the Madin-Darby canine kidney (MDCK) cells cultured in sample Mg67Zn29Ag4 and its extraction medium have higher activity. However, the Mg-Zn-Ag metallic glasses exhibit obvious inhibitory effect on human rhabdomyosarcoma (RD) tumor cells. The present investigations on the glass-forming ability, corrosion behavior, cytocompatibility and tumor inhibition function of the Mg-Zn-Ag based metallic glass could reveal their biomedical application possibility.

New-generation biocompatible Ti-based metallic glass ribbons for flexible implants

We introduce five new biocompatible Ti-based metallic glass (MG) compositions with different metalloid and soft metal content for a synergistic improvement in corrosion properties. Without any potentially harmful elements such as Cu, Ni or Be, these novel alloys can eliminate the risk of inflammatory reaction when utilized for permanent medical implants. Excluding Cu, Ni or Be, which are essential for Ti-based bulk MG production, on the other hand, confines the glass-forming ability of novel alloys to a moderate level. In this study, toxic-element free MG alloys with significant metalloid (Si–Ge–B, 15–18 at.%) and minor soft element (Sn, 2–5 at.%) additions are produced in ribbon form using conventional single-roller melt spinning technique. Their glass-forming abilities and their structural and thermal properties are comparatively investigated using X-ray diffraction (XRD), synchrotron XRD and differential scanning calorimetry. Their corrosion resistance is ascertained in a biological solution to analyze their biocorrosion properties and compare them with other Ti-based bulk MGs along with energy dispersive X-ray. Ti60Zr20Si8Ge7B3Sn2 and Ti50Zr30Si8Ge7B3Sn2 MG ribbons present a higher pitting potential and passivation domain compared with other Ti-based MG alloys tested in similar conditions. Human mesenchymal stem cell metabolic activity and cytocompatibility tests confirm their outstanding cytocompatibility, outperforming Ti-Al6-V4.

Influence of partial substitution of Ti for Al on microstructure, thermal stability and corrosion resistance of novel quaternary Ni33.3Y33.3Al33.4-xTix medium entropy metallic glasses

In this present study, the influence of partial substitution of Ti for Al on microstructure, thermal stability and corrosion resistance of novel quaternary low-density Ni33.3Y33.3Al33.4-xTix (x = 3∼21 at.%) medium entropy metallic glass ribbons (ME-MG ribbons) was investigated. According to the rule of atomic radius similarity, by gradually replacing Al by Ti, we have synthesized a series of multi-component glassy alloy ribbons via using a single roller melt-spinning technique and also have examined their phase structure, thermal characteristics, microhardness and anti-corrosion properties. Besides, the phase composition of some representative annealed ribbon samples and the crystallization activation energy of these melt-spun ME-MG ribbons have been also determined and studied in detail. Results show that all of the rapidly solidified alloy ribbons can maintain completely amorphous nature. However, the thermal stability of ME-MG ribbons becomes reduced with the increasing Ti content. The maximum crystallization onset temperature at the heating rate of 20 K/min is around 706.65 K for Ni33.3Y33.3Al30.4Ti3 alloy ribbons. The maximum apparent activation energy of crystallization by means of thermodynamic analysis can be up to ∼803 kJ/mol for Ni33.3Y33.3Al21.4Ti12 alloy ribbons. The average microhardness value of these metallic ribbons can reach 455 HV0.1 or more when Ti content is less than 15 at.%, which is approximately 1.5 times the hardness of the Al-based amorphous alloy ribbons. The microstructural characterization of each ME-MG ribbon surface in as-received state and after a period of 45-hour and 75-hour corrosion immersion in 0.6 M NaCl solution was applied by scanning electron microscopy as well. Substituting moderately Al with Ti can effectively improve the anti-corrosion ability; the most positive pitting corrosion potential and the smallest corrosion current density are approximately -0.145 VSCE and 0.045 μA/cm2 for Ni33.3Y33.3Al24.4Ti9 and Ni33.3Y33.3Al27.4Ti6 ME-MG ribbons, respectively. Thus, it can be deduced that these new-fashioned ME-MG ribbons possess the superior anti-corrosion property, higher microhardness and acceptable thermal stability simultaneously, which may open momentous possibilities for the development and practical application of high-performance metal materials.

Amorphous transformation of ternary Cu45Zr45Ag10 alloy under microgravity condition

The influences of undercooling rate and cooling rate on the microstructural evolution of ternary Cu45Zr45Ag10 alloy using single-roller melt spinning and drop tube are investigated. The rapidly quenched alloy ribbons achieve a homogeneous glass structure. The microstructure of the droplets transforms from the Cu10Zr7 dendrites plus (Cu10Zr7 + AgZr) eutectic into Cu10Zr7 dendrite with the decrease of droplet diameter. As the diameter decreases to 180 μm, the Cu45Zr45Ag10 alloy changes from crystal to amorphous structure, showing that the cooling rate is not the only influence factor and the undercooling play a certain role in the forming of the amorphous alloy at the same time under microgravity condition.

Effect of the substitution of Si for B on thermal stability, magnetic properties and corrosion resistance in novel Fe-rich amorphous soft magnetic alloy

Soft magnetic alloy Fe83.3SixB16-xCu0.7 (x = 0, 1, 2, 3 and 4) ribbons were produced by the single roller melt spinning method. The Si content dependence of magnetic properties and corrosion resistance was investigated. Appropriate addition of Si is effective to the improvement of thermal stability, soft magnetic properties and corrosion resistance in this alloy system. Excellent soft magnetic properties with low coercivity 3.1 A/m and high magnetic flux density 1.66 T can be obtained when x = 1 annealed at 365 °C for 10 min. Compared with the Si-free ribbon, the corrosion resistance of the x = 1 alloy ribbon is also improved. The X-ray photoelectron spectroscopy (XPS) indicates that the formation of an SiO2-enriched passive film is mainly responsible for the high corrosion resistance of Si-containing (x = 1) alloy in 3.5 wt% NaCl solution. Low cost of raw materials, high thermal stability, good soft magnetic properties as well as excellent corrosion resistance make this alloy a promising candidate for future application.

Effect of melt cooling rate on glass transition kinetics and structural relaxation of Vit1 metallic glass

The thin ribbons and the bulk cylindrical rods with diameters of 2 mm and 10 mm of the Vit1 metallic glass (MG) were prepared by the single roller melt spinning method and the copper mold injection casting method, respectively. The cooling rates of the samples during melt solidification were evaluated. The glass transition behaviors of three groups of MG samples with different solidification cooling rates were studied by differential scanning calorimetry (DSC) at different heating rates. The effects of melt cooling rate on the glass transition kinetic parameters such as apparent activation energy (E) and fragility parameter (m) of the Vit1 MG were studied using the Kissinger and the Vogel-Fulcher-Tammann (VFT) equations. Additionally, the structural relaxation enthalpy (ΔHrel) of three groups of MG samples was quantitatively analyzed by DSC through multi-step temperature rise and fall measurements. Results show that the melt cooling rate (R) has a significant effect on the glass transition kinetics and the structural relaxation of the Vit1 MG. As R decreases in the order of magnitude, the glass transition temperature (Tg), E, m, and ΔHrel of the Vit1 MG gradually decreases. Furthermore, in the range of the experimental cooling rates, E, m, and ΔHrel all have an approximately linear relationship with lgR.

Composition optimization of Al-Ni-Ti alloys based on glass-forming ability and preparation of amorphous coating with good wear resistance by plasma spray

Al-based alloys with compositions of Al 100-x-y Ni x Ti y (x = 5, 10, 15; y = 3, 6, 9) and Al 100-x-y Ni x Ti y (x = 10; y = 12, 15) were prepared by single-roller melt-spinning. To overcome the inability to measure the glass transition temperature , the amorphous content calculated from the X-ray diffraction pattern was used to evaluate glass-forming ability. The optimized composition with the highest glass-forming ability was Al 81 Ni 10 Ti 9 . The microhardness of the Al 81 Ni 10 Ti 9 ribbons increased first and then decreased when the ribbons were annealed at temperatures from 150 to 550 °C. Precipitation of α-Al nanocrystals improved the microhardness. There was no amorphous phase in the powders based on the optimized composition prepared by the atomization method, while the amorphous content of the coating obtained by plasma spray reached up to 49.76%. This was because the cooling rate in the spray process was at least two orders of magnitude higher than that in the gas atomization process. The coating had good wear resistance and the wear mechanisms were also analyzed. • A new method to evaluate the glass-forming ability (GFA) for alloys with low GFA; • A kind of Al-based amorphous coating was prepared by the plasma spray technology firstly; • The amorphous phase was not in the atomized powders but formed during the process of plasma spray; • Al-Ni-Ti amorphous coating possess good wear resistance and application prospects on surface engineering;

Calorimetric and structural analysis of the Zr–Fe–Co–B–Mo–W amorphous alloys doped with gadolinium

Abstract The paper presents the calorimetric and structural analysis of the rapidly solidified GdxZr10Fe58-xCo10B15Mo5W2 (where: x = 0, 1, 2, 3, 4, 5) alloy ribbons in as-cast state. The base alloys were obtained by the arc-melting of the high purity constituent elements under a low pressure of Ar protective atmosphere. Subsequently, the ribbon samples were produced by the single-roll melt spinning technique under the low Ar pressure at the linear velocity of the copper roll surface of 32 m/s. X-ray diffraction (XRD) studies have shown amorphous structure of all the alloy. The microstructure of the samples was examined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) measurements were performed at various heating rates. These allowed to determine the thermal stability of the amorphous phase. The Kissinger, Ozawa and Augis-Bennett plots were constructed to determine the activation energies Ea for crystallization. The positron annihilation lifetime spectroscopy (PALS) was used to study the structural changes as well as a degree of disorder in the atomic structure caused by doping the base alloy with Gd.

Characterization of new catalysts prepared by in-situ activation of Ce50Ni50-xAux intermetallic compounds for CO oxidation

In this study, catalysts for CO oxidation were prepared through in-situ activation of Ce50Ni50-xAux intermetallic compounds and characterized; these included Ce50Ni50 and Ce50Ni45Au5. Ribbon samples of intermetallic compounds were fabricated by single-roller melt spinning and then ground into powders for subsequent analysis. XRD patterns of the compounds were indexed as orthorhombic symmetry and no second phase was detected within the limits of low XRD resolution, indicating a homogeneous nature. Among the catalysts evaluated, the metal-oxide complex consisting of Ni–Au and CeO2, synthesized from the in-situ activation of Ce50Ni45Au5 compounds, showed a better catalytic activity for CO oxidation. In the presence of CO, Ce oxidation is thermodynamically favored while Ni oxidation is inhibited. The catalyst of the metal-oxide complex prepared from the Ce50Ni45Au5 compound revealed the CO conversions of 28.1%, 76.3%, 96.3% and 97.1% at reaction temperatures of 100 °C, 150 °C, 200 °C and 250 °C, respectively. SEM results revealed that a large quantity of fine Au–Ni particles were distributed on the CeO2 support after thermal treatment, which contributed to the high CO conversion over the Ce50Ni45Au5 compound at temperatures below 200 °C. Compared with the results in the literature, the high catalytic activity of the Ce50Ni45Au5 intermetallic compound, with a low Au loading of 7.6 wt% and a low surface area of 1.1 m2/g, displayed the most beneficial characteristics for practical applications.

Achievement of superior microwave absorption performance and ultra-wide regulation frequency range in Fe-Co-Nd via tuning the phase constitution and crystallinity

To achieve superior microwave absorption and ultra-wide regulation frequency range under a restricted thickness, (FeCo)100−xNdx (0 ≤ x ≤ 15) powders were prepared through a single roller melt spinning technique. The introduction of Nd decreases the crystallinity of FeCo phase and promotes the formation of secondary Nd2(FeCo)17 phase, which results in apparent reduction of electromagnetic (EM) parameters. The correlations between EM parameters and final microwave absorption properties are discussed in detail. It is found that the suppressed EM parameters modifies the coordination between impedance matching and attenuation performance, ultimately leading to superior microwave absorption performance with broad bandwidth of 6.92 + GHz and RLmin of −52.5 dB under thickness of only 1.45 mm. Moreover, due to the dramatic decline of |μr|·|εr| values, the qualified RL of the samples covers almost all the test frequency (2–18 GHz) with thin thickness of 2 mm, showing great practical value in full-spectrum microwave absorption area with a restricted coating thickness.

The composition design and properties investigation of Al-based amorphous powder

By adding different amounts of rare earth element Y and Gd in Al86Ni8Co1La5, aluminum amorphous ribbon samples were prepared using single roller melt-spinning under 2 different roller speeds. Then X-ray diffraction (XRD), transmission electron microscope (TEM) and differential scanning calorimetry (DSC) were adopted to study the effect of rare earth element Y and Gd additions on phase structure, forming ability and thermal stability of Al86Ni8Co1La5 alloy. The results show that the better chemical composite is Al86Ni8Co1La1Y2Gd2, which can form a whole amorphous strip when the roller speed is 3 m/s. After the better chemical composition is confirmed, the Al-based amorphous powder is produced using gas atomization and its properties are also validated using cold spray technique. The thickness, porosity and amorphous amount of coatings is about 600 μm, 0.5% and 80.2% (CS–C), respectively. These findings indicate that Al86Ni8Co1La1Y2Gd2 amorphous powder can be used as raw materials for cold spray technique.

A Multiple Twin-Roller Casting Technique for Producing Metallic Glass and Metallic Glass Composite Strips.

To date it has not been possible to produce metallic glass strips with a thickness larger than 150 μm via single-roller melt spinning technique, and it remains challenging to produce thick metallic glass strips. In this work, a multiple twin-roller casting technique is proposed for producing thick metallic glass and metallic glass composite strips. A triple twin-roller casting device, as a specific case of the multiple twin-roller, was designed and manufactured. The triple twin-roller device possesses a high cooling rate and involves a long contact time between the melt and the strip, which makes it an efficient technique for producing metallic glass strips that avoids crystallization, although the solidification temperature ranges of metallic glasses are as wide as several hundred Kelvins. The two prepared metallic glass (MG) strips are in a fully amorphous state, and the MG strip shows excellent capacity of stored elastic energy under 3-point bending. Furthermore, the Ti-based metallic glass composite strip produced via the triple twin-roller casting exhibits a novel microstructure with much finer and more homogenously orientated β-Ti crystals, as compared with the microstructure of metallic glass composites produced by the common copper mold casting technique.

Rejuvenated metallic glass strips produced via twin-roll casting

The energy state and atomic level structure of metallic glasses (MGs) are very sensitive to their cooling rates, and a lower cooling rate generally causes a lower energy and more relaxed state of MGs. In this work, the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit. 1) ribbons with a thickness of 40 μm and 110 μm and the strips with a thickness of 320 μm and 490 μm were produced by single-roll melt spinning and twin-roll casting, respectively. The increase in thickness of either ribbons or strips results in a lower energy state with a smaller relaxation enthalpy, a lower content of free volume, and a higher hardness. Although the cooling rate of the twin-roll produced 320 μm-thick strip is almost one magnitude lower than that of the single-roll produced 110 μm-thick ribbon, the former, however, possesses a rejuvenated energy state as compared to the latter. Molecular dynamics simulations reveal that the squeezing force during twin-roll casting affects the evolution of connection types of clusters, and the 2-atom and 4-atom connections are prone to be retained, which results in a higher energy state of MGs. Such a rejuvenation process during twin-roll casting can overwhelm the relaxation process caused by the lower cooling rate. Therefore, twin-roll casting is not only a method being capable for producing strips with a large thickness, but also prone to obtain a high energy state of the MG strip.

Tailoring magnetic characteristics of (Fe1−xCox)81Zr9B10 amorphous alloys via engineering crystallization processes

We report on systematic structural and magnetic characteristics’ evolution studies of (Fe1−xCox)81Zr9B10 (x = 0, 1/6, 1/3, 1/2) amorphous alloys prepared by a single roller melt spinning with post-annealing treatments under a vacuum condition. With representative chemical composition, the crystallization processes of the above four typical amorphous alloys are complicated under the dedicated experimental investigations and interpretation. The α-Mn-type phase is detected in Fe81Zr9B10 alloy, while the β-Mn-type phase is observed for high Co concentration alloys. Both α-Mn-type phase and β-Mn-type phase are the transitional metastable phases formed during the dynamic crystallization. Importantly, the precipitations of metastable α-Mn- and β-Mn-type phases boost up corresponding coercivity (Hc). Along with the transformation of metastable phases, Hc decreases considerably. The precipitation of certain of β-Mn-type phase in the primary crystallization stage facilitates gaining low Hc in the second stage of crystallization. Our work paves a new path to tailor the magnetic characteristics in Fe(Co)-based nanocrystalline alloys by engineering the microstructure of metastable phase(s).