Fe-based Metallic Glass Powders Research Articles

Simultaneously healing cracks and strengthening additively manufactured Co34Cr32Ni27Al4Ti3 high-entropy alloy by utilizing Fe-based metallic glasses as a glue

Solidification cracking issues during additive manufacturing (AM) severely prevent the rapid development and broad application of this method. In this work, a representative Co34Cr32Ni27Al4Ti3 high-entropy alloy (HEA) susceptible to crack formation was fabricated by selective laser melting (SLM). As expected, many macroscopic cracks appeared. The crack issues were successfully solved after introducing a certain amount of Fe-based metallic glass (MG) powder as a glue during SLM. The effect of MG addition on the formation and distribution of defects in the SLM-processed HEA was quantitatively investigated. With an increasing mass fraction of the MG, the dominant defects transformed from cracks to lack of fusion (LOF) defects and finally disappeared. Intriguingly, the MG preferred to be segregated to the boundaries of the molten pool. Moreover, the coarse columnar crystals gradually transformed into equiaxed crystals in the molten pool and fine-equiaxed crystals at the edge of the molten pool, inhibiting the initiation of cracks and providing extra grain boundary strengthening. Furthermore, multiple precipitates are formed at the boundaries of cellular structures, which contribute significantly to strengthening. Compared to the brittle SLM-processed Co34Cr32Ni27Al4Ti3 HEA, the SLM-processed HEA composite exhibited a high ultimate tensile strength greater than 1.4 Ga and enhanced elongation. This work demonstrates that adding Fe-based MG powders as glues into SLM-processed HEAs may be an attractive method to heal cracks and simultaneously enhance the mechanical properties of additively manufactured products.

Effect of Fe-based metallic glass on microstructure and properties of Hastelloy X manufactured by laser powder bed fusion

Hastelloy X is widely used in aerospace because of its excellent high-temperature performance. Laser powder bed fusion (LPBF) can be used to manufacture Hastelloy X and its reinforced materials with more complex structures and better performance. In this study, Hastelloy X reinforced materials added Fe-based metallic glass powder was manufactured using LPBF, and four sequences of 0, 3, 5, and 7 wt%. The introduction of Fe-based metallic glass powder has exhibited notable improvements in the mechanical properties at room and high temperatures. At room temperature (RT), the 5 wt% reinforced material exhibited a larger increase in hardness, with a yield strength and ultimate tensile strength of 856Mpa and 1081 MPa, and the reduction in elongation was only 9.6%. At high temperatures, introducing Fe-based metallic glass enhanced the yield strength and ultimate tensile strength, and the elongation was greatly improved at 800 ℃. The enhancements are mainly due to the grain size refinement caused by the introduction of Fe-based metallic glass powder, which increases dislocation density and grain boundary strengthening. In addition, as the content of Fe-based metallic glass increased, the corrosion resistance of the samples was also improved due to increased Cr and W content and the refinement of grains. This study provides a new research direction for improving the properties of Hastelloy X.

Structural evolution of MgO layer in Mg-based composites reinforced by Metallic Glasses during the SPS sintering process

The SPS sintering process is used in this study to create 50 wt % micro-sized spherical Fe-based metallic glass powders reinforced magnesium matrix composites (FMGP). The release of trace amounts of Cr in Fe-based metallic glass particles due to a positive mixing enthalpy with Mg not only improves the mechanical suitability of the interface between the metallic glass and the matrix but also contributes to the solution to the increasing problem of fracture toughness of the composite. Following the inclusion of metallic glass particles (50 wt %), the tensile strength (23%), yield strength (50%), and plasticity (more than 8%) were significantly increased. The Cr diffused to the interface and dissolved into the MgO in the form of replacement, forming the oxidation transition layer with the MgO and α-Mg at the interface and distributed among a discontinuous form, according to the analysis of the high-resolution transmission diagram of the composites and the calibration of the diffraction spots of the magnesium matrix at the interface. This enhances mechanical interface matching and transforms the composite's fracture process from inter-crystalline to quasi-destructive, increasing the material's fracture toughness. Once established, the model's first-principles computation and analysis are consistent with the test results.

Efficient degradation of orange II dye using Fe-based metallic glass powders prepared by commercial raw materials

An efficient, economical and reusable Fe-based metallic glass (MG) powders were prepared for degrading Orange II solution. The influence parameters such as initial pH, temperature, recycle times and initial Orange II concentration were investigated for the degradation efficiency. The experimental result shows that 98.6% degradation rate was achieved within 2 min using low dosage Fe–Si–B–P–C glassy powders at acidic pH value. In addition to the metastable properties of glassy powders, the excellent degradation performance can relate to the spongy porosity of powder surface appeared during degradation treatment. We also found that the degradation rate improved obviously with the increase of temperature or acid strength in solution. After recycle experiment of six times, the glassy powders still maintained high degradation efficiency to Orange II solution. This work will contribute to the development of cheap and high quality glassy powders with excellent ability to degrade azo dyes.

Mechanical properties and tribological behavior of aluminum matrix composites reinforced with Fe-based metallic glass particles: Influence of particle size

Aluminum matrix composites consisting of Al2024 and Fe-based metallic glass powders were prepared via powder metallurgy by using an optimized matrix to reinforcement particle size ratio, the influence of glassy particle size on mechanical properties and dry sliding wear behavior of the composites were investigated. The composites showed dense structure and homogenous three-dimensional distribution of the reinforcements independent of particle size. The particle size has negligible influence on yield strength, while ultimate tensile strength and ductility gradually decrease with increasing particle size. Reduced specific wear rate was observed when particle size increases, most likely because of the evolution of the surface topography during sliding where the wear of matrix is protected when particles are large.

Comparison of tribological behavior of Fe-based metallic glass coatings fabricated by cold spraying and high velocity air fuel spraying

High wear between surfaces may lead to an increase of cost of production in mechanical engineering industry. To solve this problem, Fe-based amorphous coatings prepared using appropriate technology can provide an effective and economical surface protection. In this work, Fe-based metallic glass powders were deposited by cold gas dynamic spraying (CGDS) and high velocity air fuel (HVAF) technology onto 35CrMo steel alloy. Scanning electron microscopy, energy dispersive X-Ray spectroscopy and microhardness measurement were employed to identify the morphology, microstructure, thickness, porosity, elements distribution and hardness of the as-sprayed coatings, while X-ray diffraction and thermogravimetry and different thermal analysis were applied to clarify the amorphous nature. The dry sliding wear tests were conducted using a ball-on-plate linear tribometer with the counter-face of ZrO2. The worn surface and worn-off debris collected after friction were studied to investigate the wear mechanism. The results display a denser and more uncrystallized structure of CGDS coating than HVAF coating. Moreover, CGDS coating has lower coefficient of friction (COF) and wear rate at different applied loads, indicative of improved wear-resistance.

Interpretation of densification behavior of spark plasma sintered Fe-based metallic glass powders from the standpoint of internal friction

In this study, Fe-based bulk metallic glass (BMG) was fabricated using spark plasma sintering (SPS) method and compacts with various densities were obtained at different temperature. To better understand the densification process of metallic glass powders, internal friction was employed to study the internal structural evolution as a function of temperature. Three stages were found in the dynamic relaxation spectroscopy, and exhibited mechanical behavior was closely related to the densification process. By further analyzing relaxational dynamics using Quasi Point Defects (QPD) theory, the correlation factor χ which is indicative of atomic mobility was calculated. The results showed that χ increased sharply above Tg, suggesting intensified atomic motion in super-cooled liquid region (SLR). Furthermore, χ reaches peak value at two adjacent crystallization peak respectively, indicating the feasibility of improving compact density at second crystallization temperature range above SLR. The combination of strengthened atomic motion induced activated diffusion and superplastic deformation of MG powders in SLR facilitated densification of MG powders concurrently.

Consolidation of Fe-Based Metallic Glass Powders by Hot Pressing

An alternative route to obtain bulk metallic glasses is by consolidation of metallic glass powders by deforming these materials in the temperature interval between the crystallization temperature and the glass transition temperature, where the material flows with a reduced viscosity. In the present work, bulk parts of the Fe43.2Co28.8B19.2Si4.8Nb4 alloy were produced by hot-pressing gas-atomized powders (GAP) under different uniaxial pressures. Different microstructural analysis revealed that the initial powder as well as the consolidated parts were mostly amorphous, with similar transformation temperatures, showing that bulk samples of this alloy can be produced by conformation in the supercooled liquid region. The sample conformed under the highest pressure (1GPa) exhibited the highest relative density of 96.1±0.5%. These results show that hot pressing of Fe-based gas-atomized powders is a promising route for producing Fe-based bulk metallic glasses.

Optimization of Sintering Time and Holding Time for 3D Printing of Fe-Based Metallic Glasses

Fe-based metallic glasses are amorphous alloys with high strength, high hardness, and excellent corrosion resistance; however, the immaturity of processing methods has prevented their wide application in industrial production. Fe-based metallic glass parts were manufactured employing pneumatic injection additive manufacturing in this study. An evenly dispersed and stable Fe-based metallic glass powder slurry with a solids content of 50% was prepared firstly. Then the Fe-based metallic glass parts were printed. The printed parts were dried, debinded, and sintered for strengthening. The deformations of the printed parts and sintered parts relative to the original model were then analyzed by a 3D scanning reconstruction method. The slightly average bulging and sunken deformation of the printed parts and sintered parts confirmed the good printing accuracy of the pneumatic injection manufacture system. The effects of the sintering temperature and holding time on the properties of the sintered parts were studied. For a sintering temperature of 580 °C and holding time of 1 h, the surface quality of the sintered parts was better. The sintering of 3D-printed Fe-based metallic glass parts was preliminarily realized in this study, and the feasibility of preparing Fe-based metallic glass using pneumatic injection additive manufacture was verified.

Study of printing parameters of pneumatic-injection 3D printing of Fe-based metallic glass

A helpful method to process Fe-based metallic glass called pneumatic-injection 3D printing is proposed. Considering the characteristics of Fe-based metallic glass particles, such as large particle size, high density, and complex surface ions, their wettability and suspension stability were investigated using experiments based on the Washburn equation. The effect of pH value, powder's morphology and granularity on wettability was qualitatively analyzed. Multiple dispersants for the slurries of Fe-based metallic glass powder were tested. The experimental results revealed the wettability of the spherical powder with a size range of 45–200 μm was relatively high. An alkaline environment was not conducive to the wetting and stable dispersion. Ammonium polyacrylate was found to be the best dispersing agent for the Fe-based metallic glass powder. A uniform, stable Fe-based metallic glass slurry with a solid content of 50% was prepared. The width of the printed line increased with the pressure and decreased with increasing nozzle speed. The study of printing parameters provides guidance to improve the quality and accuracy of pneumatic-injection 3D printing of metallic glass.

Mechanism and kinetics of treatment of acid orange II by aged Fe-Si-B metallic glass powders

The mechanism and kinetics of acid orange II (AOII) treated by aged gas-atomized Fe-Si-B metallic glass (MG) powders were investigated in this study. The decolorization reaction is shown to obey the pseudo-first-order kinetic model, and the treatment processes could be divided into two stages: a slow step followed by a rapid one. This observation is in accordance with the following results, the azo dye is simply adsorbed onto the Fe-based MG powders in the initial stage, because the oxide layer coated on the powder surface depresses the degradation reaction by covering the activity sites, and then the degradation occurs with the desquamation of the powders. The AOII could be degraded with a rapid reaction rate when the Fe-based MG powders are applied to the treatment process again, because of the consumption of the oxide layer and the unchanged core of the Fe-based MGs. These findings will promote the practical application of MGs in degrading azo dyes.

A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders.

A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

Metastable microstructures containing zero valent iron for fast degradation of azo dyes

A novel iron powder obtained by ball milling ribbons of a rapidly solidified cast iron was tested for azo dye degradation in aqueous solution versus commercial Fe and a Fe-based metallic glass powders. The cast iron powders were at least as efficient in promoting the degradation reaction of ethyl-orange and direct blue-6 as the ball-milled metallic glass: dyes decomposition was complete in about an hour. The efficiency of alloy samples increases as a function of the decrease of particles size and does not appear to be strongly due to the structure of the phase containing Fe. The main reason for catalytic efficiency is the presence of metastable phases in the material. The zero valent iron that they contain is more prone to provide electrons for the degradation of N–N double bonds. The starting material is cheap and the sample preparation is straightforward. Therefore, it is believed these samples are suitable for fast degradation at room temperature of azo dyes compared with metallic glasses recently proposed in the literature.

Corrosion Resistance of Coating with Fe-based Metallic Glass Powders Fabricated by Laser Spraying

Corrosion Resistance of Coating with Fe-based Metallic Glass Powders Fabricated by Laser Spraying

Effect of Zr on Microstructure of Metallic Glass Coatings Prepared by Gas Tunnel Type Plasma Spraying

Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared.