Fe-containing Alloy Research Articles

Creating heterostructures via laser powder bed fusion using titanium and stainless steel mixtures

This study addresses the challenge of breaking the trade-off dilemma between strength and ductility in additively manufactured Titanium (Ti) products. By leveraging concentration non-uniformity and controlled diffusion during in-situ alloying of unalloyed titanium (CP-Ti) and 316L stainless steel (SS316) powders via laser powder bed fusion (LPBF), we formulated a novel Fe-containing alloy with improved printability and enhanced mechanical performance. The microstructure of the as-built Ti alloy comprises a heterostructure of nano-scaled martensitic α′ within the micro-scaled equiaxed prior-β grains, resulting from rapid solidification inherent in LPBF. Since the modified laser-powder bed fusion in this work lacks a pre-heating function, a stress-relief annealing process was conducted to enhance the mechanical properties of the as-built parts. The annealed in-situ alloyed Ti-Fe achieves a superb balance between strength and ductility, with an ultimate tensile strength (UTS) of approximately 1118.0 MPa and an elongation of ∼9.0 %. This study provides insights for designing high-performance Ti alloys with heterostructures using a mixture of elemental powder and alloyed powders via LPBF. The significance of concentration non-uniformity and diffusion during solidification is highlighted, demonstrating how these factors contribute to the formation of superior heterostructures through additive manufacturing.

Effect of Initial Fe Content on Microstructure and Mechanical Properties of Recycled Al-7.0Si-Fe-Mn Alloys with Constant Mn/Fe Ratio.

The effect of initial Fe content on the iron removal efficiency, morphology evolution of the Fe-rich phase and the mechanical properties of the recycled Al-7Si-xFe-1.2xMn alloy during melt holding was studied using an optical microscope (OM), scanning electron microscope (SEM) and tensile testing. The results show that with the increase of the initial Fe content, the residual Fe concentration of the alloys gradually increased, and the corresponding removal efficiency of Fe gradually was increased to 77.67%. The type of Fe-rich phase in the alloys changes from α-Al15(FeMn)3Si2 to a mixture of α-Al15(FeMn)3Si2 and β-Al5FeSi, and its morphological evolution is as follows: coarse Chinese-script + polygon → dense Chinese-script + polygon → polygonal + dense Chinese-script + plate-like. Furthermore, the morphology of the Fe-rich phase in the slag changes from a polygonal shape to an irregular shape with a two-layer structure. The formation and increase of the inner layer with high Mn-content in the irregular-shape phase is the main reason for the increasing residual Fe content. The plasticity of the alloy increases obviously with the increase of the initial Fe content, but the formation of the β-Al5FeSi with plate-like morphology in higher Fe-containing alloy may hinder further improvement of the plasticity.

Tribological Behavior of Microalloyed Cu50Zr50 Alloy

Abstract Promoting the martensitic transformation through optimum microalloying with Fe and/or Mn was observed to be an effective method to enhance the wear resistance of the Cu50Zr50 at% shape memory alloy (SMA). Among all the potential microelements and concentrations, partial replacement of Cu by up to 1 at% Fe and Mn is of interest since from density functional-based calculations, large minimization of the stacking fault energy (SFE) of the B2 CuZr phase is predicted. For this reason, an effective martensitic transformation is expected. The largest decrease of the SFE from 0.36 J/m2 to 0.26 J/m2 is achieved with partial replacement of Cu by 0.5 at% Fe. This results in the highest martensitic transformation upon wear testing, especially at highest load (15 N) for which the mass loss is 0.0123 g compared to 0.0177 g for Cu50Zr50 and a specific wear-rate of 5.9 mm3/Nm, compared to 8.5 for mm3/Nm for Cu50Zr50. This agrees with the low coefficient of friction of 0.48 ± 0.05 and low roughness of 0.200 ± 0.013 µm of the Fe-containing alloy compared to that for Cu50Zr50, 0.55 and 0.415 ± 0.026 µm, respectively. All the worn surfaces show the formation of abrasive grooves, being shallowest for the more wear resistant 0.5 at% Fe alloy. The second more wear resistant alloy contains 0.5 at% Mn. Wear mechanisms of abrasion, adhesion, and delamination have been identified.

Effects of temperature and loading rate on phase stability and deformation mechanism in metastable V10Cr10Co30FexNi50-x high entropy alloys

Room- and cryogenic-temperature compressive properties for the three V10Cr10Co30FexNi50-x (x = 40, 45, 50) high entropy alloys are investigated under quasi-static and dynamic loading conditions. The face-centered cubic (FCC) stability, which is estimated by the calculation of Gibbs free energy difference between FCC and body-centered cubic (BCC) phases, decreases in increasing order of Fe content. The 40Fe and 45Fe alloys consist of FCC single phase, whereas the 50Fe alloy is composed of a duplex structure with ~95 vol% of body-centered cubic (BCC) lath martensite. Under the quasi-static loading condition at room temperature, the dislocation slip prevails in the 40-at.%-Fe-containing alloy, while the twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) are activated in the other alloys. The decrease in testing temperature lowers the FCC stability, activating both TWIP and TRIP mode. Under the dynamic loading, the magnitude of TWIP effect enhances, but that of TRIP effect reduces in comparison to the quasi-static loading. The adiabatic heating induced from the dynamic loading increases the FCC stability, thereby resulting in the reduced TRIP effect. Despite the increased stability, the TWIP occurs more actively because the dynamic loading enables the increased flow stress to readily exceed the critical stress required for TWIP. These variations of deformation mechanisms according to the FCC stability, testing temperature, loading rate, adiabatic heating effect, and increased flow stress effect are systematically correlated by the shifting of stability on the slip-TWIP-TRIP mechanism band.

Towards ferrous medium-entropy alloys with low-cost and high-performance

This article introduces a practical and straightforward strategy to take a paradigm shift in the high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) design concept from equiatomic alloys towards cost-effective ferrous medium-entropy alloys (FeMEAs). Upon deviating from the equiatomic composition in Fe-containing alloy system, we show that various FeMEAs can be developed by pseudo-binary methods. Further, we discuss an overview of the microstructural evolution and mechanical properties of recently-developed FeMEAs, which exhibit a broad spectrum of microstructures and mechanical properties. This viewpoint article highlights insights into the concept of FeMEAs, providing a potential direction for future development of HEAs and MEAs.

Effect of Bifilm Oxides on the Dry Sliding Wear Behavior of Fe-Rich Al–Si Alloys

The effect of bifilm oxides on the dry sliding wear behavior of Fe-rich (1.5 wt.%) F332 Al–Si alloy under as-cast and T6 heat-treated conditions was investigated. Toward this end, the surface oxides were intentionally incorporated into the molten alloy by surface agitation. The results showed that, after sliding under the applied load of 75 N, due to the presence of bifilms, the wear rate of base (0.2 wt.% Fe) and 1.5 wt.% Fe-containing alloys increased by almost 22% and 14%, respectively. The results also indicated that, despite the positive effect on the hardness, T6 heat treatment adversely affected the wear resistance of alloys made under surface turbulence condition. This negative effect can be attributed to the expansion of bifilms which, during heat treatment, are converted to the potential sites for initiation and propagation of subsurface microcracks. However, the strengthening effect exerted by the thermally modified β-Al5FeSi platelets showed that it can compensate the negative effects of bifilm oxides because it improves the wear rate of 1.5 wt.% Fe-containing F332-T6 alloy by about 5% under the applied load of 75 N.

Enhanced Flux Pinning and Microstructural Study of Single-Domain Gd-Ba-Cu-O Bulk Superconductors With the Addition of Fe-Containing Alloy Particles

Introducing secondary-phase inclusions, especially magnetic particles, into the superconducting matrix is regard as an effective way to enhance the performance of high-temperature superconductors. The effect of Fe-B alloy additives on the microstructure and superconducting properties of top-seeded melt growth processed Gd-Ba-Cu-O bulk superconductors has been investigated systematically. Gd-Ba-Cu-O bulks 17 mm in diameter were melt-textured for various amounts of Fe-B additives in the range of 0-1.4 mol%. With the observations of scanning and transmission electron microscopy, the Fe-B alloy additives were found to decompose into Fe-containing particles with submicrometer in diameter. The refinement and homogeneous distribution of Gd2BaCuO5 inclusions seems to be improved remarkably. It leads to enhance flux pinning, flux trapping capability, and critical current density of Gd-Ba-Cu-O bulks, correspondingly. This phenomenon might be related to the magnetic interactions between the Fe-containing particles and the surrounding components, which may be the origin of the improvement of Gd2BaCuO5 nucleation process.

Effects of ultrasonic vibration on the iron-containing intermetallic compounds of high silicon aluminum alloy with 2% Fe

Abstract The effects of ultrasonic vibration (USV), the combined effects of USV and the addition of Mn on the morphology of iron-containing intermetallic compounds of Al–20Si–2.0Fe–2.0Cu–0.4Mg–1.0Ni alloy have been studied respectively. The mechanism of shape-transformation of Fe-containing phases is also investigated. A large amount of long needle-like β-Al5FeSi phases accompanied with a few δ-Al4FeSi2 phases existed in the matrix of high silicon aluminum alloy with 2% Fe in traditional casting process. The effects of acoustic cavitation and acoustic streaming generated by USV which was applied near the liquidus temperature of this alloy, homogenized the solute distribution field and temperature field of the melt, lowered the concentration level of Fe atoms in solidification front, and decreased the start-freezing temperature of β phase. That the formation of acicular β phase was suppressed, contribute to enlarge the forming temperature range of δ phase of the alloy with certain time of USV imposed near the liquidus temperature. The finest δ particles and only a small amount of β phase were obtained in the matrix of the Fe-containing alloy with USV for 120 s. With the complex effects of USV and addition of 0.5% Mn, the forming of acicular β phase was almost repressed and the Fe-containing phases were in forms of fine Al4(Fe,Mn)Si2 and Al5(Fe,Mn)Si particles in the size of 20–30 μm.

Thermal Stability and Mechanical Properties of Ti<SUB>47.4</SUB>Cu<SUB>42</SUB>Zr<SUB>5.3</SUB>TM<SUB>5.3</SUB>(TM = Co, Fe) Metallic Glass Sheets Prepared by Twin-Roller Casting Method

Since Ti-based glassy alloys have high strength and high corrosion resistance, it is useful for an application field of substitution material for biomaterials such as living body bone. For the biomaterial use, the glassy alloys are required to substitute the harmful elements for the human body such as Ni. In the present study, we prepared the Ti47.4Cu42Zr5.3TM5.3(TM = Co, Fe) glassy alloy sheets by a twin-roller casting method, and investigated their thermal stability and mechanical properties. The prepared alloy sheets had flat surfaces with highly white luster, and exhibited a distinct glass transition typical to a glassy phase. The super-cooled liquid region ΔTx defined by the difference between the glass transition temperature (Tg) and the onset temperature for crystallization (Tx) is 50 K for the Ni-containing alloy, 36 K for the Co-containing alloy and 32 K for the Fe-containing alloy. All the alloy sheets exhibit good bending ductility and their Vickers hardness is in the range of 590 to 600.

TiAl基合金の高温酸化挙動に及ぼすH2O, CO2およびN2の影響

TiAl-based alloys (Ti-48Al-2Cr-2Nb, Ti-48Al -2Cr-2Fe, Ti-48Al-2Cr-2W and Ti-48Al-2Cr-1W-1Ta in mol%) were oxidized isothermally at 1123 K for 360 ks in a flow of O2, O2-H2O, H2O, O2-CO2, CO2, O2-N2 or N2 and the influence of H2O, CO2 and N2 in the oxidizing atmosphere on the oxidation behavior has been studied. The oxidation of Nb, W or Ta containing alloys in O2 results in the formation of continuous Al2O3 layers in the scales and thus in superior oxidation resistance. On the other hand, the alloy with Fe shows large mass gains due to oxidation without forming a continuous Al2O3 layer. The presence of H2O in the atmosphere accelerates the oxidation of all the alloys, and this influence is prominent for the Fe-containing alloy. Since H2O affects more significantly TiO2 than Al2O3, the observed influence of H2O is attributable to the anisotropic and enhanced growth of TiO2. While the oxidation behavior of the alloy with Fe is affected by the presence of CO2, the other alloys are not susceptible to it. Although N2 is less influential than H2O and CO2, the alloys with Nb, W or Ta show larger mass gains in O2-N2 than in O2. The influence of CO2 or N2 is attributable to the formation of carbides or nitrides respectively in the scales that impede the continuity of the protective Al2O3 layers. The influence of these gas species is smaller for the alloys forming protective Al2O3 layers in the scales and vice versa.

Structure and magnetocaloric properties of the Fe-doped HoTiGe alloy

The structure and magnetocaloric properties of the Fe-doped HoTiGe compound were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy, x-ray diffraction, magnetometry, and calorimetry. As with the early studies on the undoped compound, the Fe-containing alloy exhibited an antiferromagnetic-to-paramagnetic transition and a magnetocaloric effect peak at 90K. The magnetization (M) versus temperature (T) data showed peaks at 10 and 90K, while M versus field (H) curves showed the presence of a field-induced transition for all T<120K; additionally, for all T<60K, open hysteresis loops at the magnetic transitions were observed. XRD measurements between 10 and 60K under various magnetic fields up to 3184kA∕m (40kOe) showed that the hysteresis was not accompanied by any change in crystallography. The magnetization derived entropy change −ΔSm vs T plot also showed the presence of two peaks, at 20 and 90K; but below 15K, −ΔSm increased steeply with decreasing temperature. It is believed that the minor phases in the Fe-doped alloy give rise to the magnetization-derived −ΔSm peak at 20K. The heat-capacity-derived −ΔSm vs T plot for the Fe-doped alloy also showed the presence of two peaks at 20 and 90K. However, the heat-capacity-derived −ΔSm did not show a rapid rise with decreasing temperature below 15K.

Influence of Fe addition on hydrogen storage characteristics of Ti–V-based alloy

In order to improve the hydrogen storage properties and reduce the cost of Ti–V-based BCC alloys, the effect of Fe substitution for part V on hydrogen absorption–desorption characteristics of Ti–10Cr–18Mn–32V alloy was investigated. It was found that proper amount of Fe addition was effective in improving the activation performance, enhancing the hydrogen absorption–desorption plateau pressure, reducing the hysteresis of hydrogen absorption–desorption plateau, increasing the hydrogen desorption capacity and decreasing the alloy's cost, while it depressed the hydrogen absorption capacity. X-ray diffraction (XRD) patterns and back scattering electron (BSE) images display that the single BCC phase of Fe-free alloy transformed into two phases of, BCC and C14 Laves, of Fe-containing alloy. Three phase transformations happened in the two alloys during the hydrogen release process, which resulted from the formation of three different hydride phases in the two hydrided alloys.

Morphology and microstructure of spring-like carbon micro-coils/nano-coils prepared by catalytic pyrolysis of acetylene using Fe-containing alloy catalysts

Three-dimensional (3D) spring-like carbon nano-coils were obtained in high purity (nearly 100%) and high yield (20%) by the catalytic pyrolysis of acetylene at 750–790 °C using an Fe-based catalyst; 54Fe–38Cr–4Mn–4Mo or 71Fe–18Cr–8Ni–3Mo (SUS513). The morphologies and microstructure were examined in detail, and the growth mechanism is also discussed. The diameter of carbon fiber, from which the carbon nano-coils was formed, was 50–200 nm, the coil diameter 100–1000 nm, and the coil pitch 10–500 nm. The nano-coils were generally grown by a mono-directional growth mode, and laces with various morphologies were very commonly observed on the surface. It was observed that the spring-like carbon nano-coils are actually composed of two fused nano-coils.

Effect of Fe and Mn additions on microstructure and wear properties of spray-deposited Al–20Si alloy

In this study, the hypereutectic Al–Si alloys were synthesized by spray atomization and deposition technique. The microstructures of spray-deposited alloys were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry sliding wear behavior of the alloys was investigated under the applied load of 8.9–35.6 N. The wear behavior of the alloys was dependent on the morphology of the intermetallics in microstructure and applied load. At lower load (8.9 and 17.8N), the Fe-containing alloy showed higher wear rate compared with the binary alloy due to the tendency for embrittlement brought about by needle-like intermetallics. At higher load (35.6 N), Fe- and Mn-containing alloy exhibited inferior wear resistance than the binary alloy due to the fragmentation of the intermetallics, thus leading to easier crack nucleation and propagation.

Morphology of zigzag carbon nanofibers prepared by catalytic pyrolysis of acetylene using Fe-group containing alloy catalysts

The morphologies of the two-dimensional (2D) zigzag carbon nanofibers obtained by the catalytic pyrolysis of acetylene using the Fe-containing catalysts are examined in detail, and the growth mechanism is also discussed. Using the alloy catalyst of Fe-38Cr-4Mn-4Mo at the reaction temperature 750–790 °C, the zigzag carbon nanofibers were formed at a higher content (20–50%) in deposits together with the twisted carbon nanocoils. The morphology of the zigzag carbon nanofibers mainly depended on the catalysts, and carbon nanofibers with various zigzag morphologies were obtained. The growth of large amounts of regular zigzag carbon fibers was observed in the presence of the high Fe-containing alloy catalyst, suggesting that the Fe element plays an important role in the formation of the regular zigzag carbon nanofibers. There is some possibility of masking or deactivating of one crystal face among the three catalyst crystal faces by the Fe element, and thus only two crystal faces are involved in the growth of the 2D-zigzag fibers while the three dimensional-helical/spiral structure of the carbon nanocoils is formed from three crystal faces.

Oxidation behavior of TiAl based alloys in a simulated combustion atmosphere

The cyclic oxidation behavior of Ti–48Al–2Cr–2Nb, Ti–48Al–2Cr–2Fe, Ti–48Al–2Cr–2W, and Ti–48Al–2Cr–1W–1Ta (at.%) was studied in a simulated combustion gas, 10O2–7CO2–6H2O–Bal. N2 (vol.%), at 1173 K for up to 1800 ks (500 h, 25 cycles). Metallographic examinations were performed for oxidized specimens using X-ray diffractometry, SEM, and EPMA. All the alloys except Fe-containing one show excellent oxidation resistance for at least 1800 ks in the test gas by forming thin and protective Al2O3-rich scales. In particular, the mass gains of the W-containing alloys are about a third of that of Ti–48Al–2Cr–2Nb. The oxidation of the Fe-containing alloy is fast and its scale repeated partial spallation. All the results are explained mainly in terms of doping effect of the additional elements to TiO2, their influence on the stabilization of the Al-depletion layer formed beneath the scale, and possible β-phase formation in the substrate. The oxidation resistance of the three alloys in the test gas is better than in the laboratory air. This was found to be due to the lower O2 content in the test gas by additional oxidation tests using another test gas containing 15%O2. Both H2O and CO2 in the test gas significantly enhance the oxidation of Ti–50Al, however they have almost no influence on the oxidation behavior of the three alloys. This indicates that these gases are influential to TiO2-rich scales but not to Al2O3-rich scales. Ta seems to behave similarly as Nb with no synergistic effect with W.