Fe Phase Research Articles

Synergistic effect of residual elements on oxidation rates and oxide/metal interface characteristics in a low-carbon steel oxidized at 1180°C for 3 hours

ABSTRACT Residual elements (Cu, Ni and Sn) of various contents have been added to a low-carbon steel to simulate the scenario of increased use of scrap during steel production. The samples were oxidized in air to represent reheating before hot rolling, using thermogravimetry analysis (TGA). Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were employed to investigate the microstructure and the enrichments at the oxide/metal interface. Results showed the residual elements had an impact on the roughness of the scale/metal interface, internal Fe oxides formation, the amount of Ni&Cu enriched Fe phase and Cu&Sn enriched liquid phase at the interface, and the depth and spacing of the liquid phase penetrations along the grain boundaries. Thermodynamic simulation predicted the effect of residual elements on liquid phases formation at the interface, with good agreement between prediction and experimental results. The influence of residual elements on the oxidation rate was discussed.

Electrochemical reactions driving Mn-enrichment in Fe[sbnd]Mn supergene ores: A mineralogical perspective

Iron and manganese oxides embody a geochemical system of great environmental, biological, and economical relevance. Chemical equilibria and the stability of FeMn phases under surface or near-surface conditions can influence the fate of contaminants in the environment, impact biological metabolic processes, or Fe and Mn phase distribution in weathered ores. In the present work, we focus on the textural, mineralogical, and chemical study of FeMn ores from the weathered zone of a vein-hosted deposit outcropping in the Iberian Pyrite Belt, SW Portugal, by means of micro-Raman spectroscopy coupled with electron microprobe microanalysis. The aims of our investigation are i) identifying the several Fe and Mn phases occurring in differently enriched ores samples, ii) relating their chemical composition with possible mineralization mechanisms, and iii) defining the mineral paragenetic pathway related to the observed textural features. Our approach enabled both the identification of the coexisting Fe and Mn phases, and unravelling paragenetic pathways leading to supergene enrichment mineralizations. Collected evidence demonstrates that changes in Eh/pH can lead to goethite dissolution under reductive conditions, promoting the release of Fe2+ into solution, whose electrochemical interaction with Mn4+ results in the formation of several types of Mn oxides, and secondary goethite. Our data shows a clear relationship between the type of Mn oxide crystallized and the ratio of aqueous Mn3+/Mn4+, alongside other prevalent cations, incorporated into tunnel or interlayer structural sites, which may be also desorbed/solubilized from primary goethite.

Upgraded lithium storage performance of defect-rich Si@C anode assisted by Fe2O3-induced pseudocapacitance

Following a flowsheet comprised of a hydrothermal reaction and a dehydration/carbonization, Si-xFe/O@C anodes featured with Fe-doping and carbon encapsulation were assembled. Comparing with pure Si, Si disseminated with in situ generated nano-scaled ferric oxide (Fe2O3) particulates displays remarkably improved cyclic performance. Fe2O3 may induce amorphization and optimize electrical conductivity, by enhancing the formation of Fe and Li2O amidst charging-discharging cycles. The as-derived Fe phase benefits the transport and storage of lithium-ion and electrons. Meanwhile, numerous tiny interfaces can be constructed between Fe granules and adjacent LixSi or Li2O, and generate pseudocapacitance. After the carbonization of resorcinol-formaldehyde resin encapsulated on Si granules, core-shell structured Si-xFe/O@C particulates can be assembled. Owing to the synergism of defect-rich structure, carbon layer well-wrapped thereon and interfacial pseudocapacitance, these nanocomposite anode materials exhibit long cyclic and upgraded rate performance. After 200 cycles, Si-0.42Fe/O@C anode retains a capacity of 929 mAh·g−1 at 1 A·g−1 and 735 mAh·g−1 at 2 A·g−1. In the rate performance test operated at 5 A·g−1, a high current density, 844 mAh·g−1 could be released. Si-0.42Fe/O@C can be charged with a specific capacity exceeding 250 mAh·g−1 over the potential range of 0.75-3 V at various current densities, demonstrating the contribution of nano-Fe pseudocapacitance effect to the energy storage of Si anodes.

Metallic cladding through microwave energy of the mixture of Ni and 15% SiC powder on AISI 304: A green approach in surface engineering

In the present study, an attempt was made to develop surface cladding on AISI 304 steel by utilizing a mixture of Ni and 15% SiC powder via microwave energy. The microwave cladding process on the AISI 304 was carried out in the in-house developed set-up on the microwave. The microwave cladding process was carried out on 900 W with a 2.45 GHz frequency for 120 seconds irradiation time. SEM images showed a uniform cladding layer and cladding surface with SiC wt.% of 15 and irradiation time of 120 seconds. The energy dispersive X-ray (EDX) pattern of AISI 304 cladding surface coating with Ni and 15% SiC. EDX pattern showed the element weight percent of Ni, Fe, Cr, Si, O, and C is 58%, 22%, 4.98%, 5.97%, 1.45%, and 7.6%, respectively. EDX pattern for the cladding layer showed the element's weight percent of Fe, Ni, Si, C, O, and Cr is 46.34%, 27.3%, 11.12%, 7.9%, 4.2%, and 3.14%, respectively. XRD of the cladding surface shows the presence of Fe, FeNi3, NiSi2, Cr2C, Ni3C, Fe2SiO4, and SiC phases. The average hardness of the cladding surface and cladding layer was found to be about 324 HV and 306 HV, respectively. The hardness of the cladding surface was improved by about 46.60%. Fatigue strength of AISI 304 without and with the microwave cladding of the mixture of 15% SiC and Ni powder was found to be 210 MPa and 245 MPa, respectively, at the cyclic load of 1 × 107 cycles. Though, a micrograph of AISI 304 with the microwave cladding of the mixture of 15% SiC and Ni powder shows the fatigue wear, wear debris, and plastic flow of SiC particles after the wear testing.

Magnetic bond-order potential for iron-cobalt alloys

For large-scale atomistic simulations of magnetic materials, the interplay of atomic and magnetic degrees of freedom needs to be described with high computational efficiency. Here we present an analytic bond-order potential (BOP) for iron-cobalt, an interatomic potential based on a coarse-grained description of the electronic structure. We fitted BOP parameters to magnetic and non-magnetic density functional theory (DFT) calculations of Fe, Co, and Fe-Co bulk phases. Our BOP captures the electronic structure of magnetic and nonmagnetic Fe-Co phases. It provides accurate predictions of structural stability, elastic constants, phonons, point and planar defects, and structural transformations. It also reproduces the DFT-predicted sequence of stable ordered phases peculiar to Fe-Co and the stabilization of B2 against disordered phases by magnetism. Our Fe-Co BOP is suitable for atomistic simulations with thousands and millions of atoms.

ОЦЕНКА ВОЗМОЖНОСТИ ИСПОЛЬЗОВАНИЯ ГИДРОЛИЗНОГО ЛИГНИНА КАК ВОССТАНОВИТЕЛЯ МЕТАЛЛОВ ИЗ ПЫЛИ ДУГОВЫХ ЭЛЕКТРОПЕЧЕЙ

Experimental results on the reduction of zinc and iron from the dust of electric arc furnaces by hydrolytic lignin in an inert atmosphere are given in the work. The thermogravimetric curve data were processed at temperatures of 700–1000 ºC. It was found that the reduction occurs in two stages: 700–800 ºC and 800–950 ºC. Samples of the original dust and those recovered at different temperatures are not single-phase, which was determined by X-ray phase analysis. In the initial dust, such phases as Fe3O4 and ZnO predominate, at 800 ºC the reflections of the FeO phase have the highest intensity, at 1000 ºC the Fe phase appears in the samples. Based on the data of thermal and X-ray phase analysis, reaction equations are proposed that underlie the process of reduction of dust metals by hydrolytic lignin.

Influences of Sn on Fe phase segregation and properties of Cu-5Fe alloy

The Cu-5Fe-xSn alloy was prepared, and the effect of Sn on Fe phase distribution, precipitation kinetics, and properties of the Cu-5Fe alloy were investigated. The tensile strength and conductivity of Cu-5Fe-0.15Sn after aging at 400°C were 712 MPa and 66.6% IACS, respectively. Compared to the Cu-5Fe alloy, the tensile strength increased by about 190 MPa, while the conductivity decreased by only 1.4% IACS. Sn optimises Fe distribution and inhibits dendritic segregation. After drawing, the Fe phase is transformed into Fe fibre. Sn enhances the synergistic deformation ability of Cu/Fe, resulting in better continuity and density of Fe fibres. The precipitation activation energies of Fe in Cu-5Fe and Cu-5Fe-0.15Sn alloys were 95.9 and 84.9 kJ/mol, respectively. HIGHLIGHTS The addition of Sn significantly improves the mechanical properties of Cu-5Fe alloy. Sn addition optimised the primary Fe phase distribution and increased the Fe fibre density. The addition of Sn reduces the ultimate solid solubility of Fe in Cu and promotes the nucleation of γ-Fe phase. Sn reduces the activation energy of Fe phase and promotes the precipitation of Fe phase.

Role of microbial iron reduction in arsenic metabolism from soil particle size fractions in simulated human gastrointestinal tract

Gut microbiota provides protection against arsenic (As) induced toxicity, and As metabolism is considered an important part of risk assessment associated with soil As exposures. However, little is known about microbial iron(III) reduction and its role in metabolism of soil-bound As in the human gut. Here, we determined the dissolution and transformation of As and Fe from incidental ingestion of contaminated soils as a function of particle size (<250 μm, 100–250 μm, 50–100 μm and < 50 μm). Colon incubation with human gut microbiota yielded a high degree of As reduction and methylation of up to 53.4 and 0.074 μg/(log CFU/mL)/hr, respectively; methylation percentage increased with increasing soil organic matter and decreasing soil pore size. We also found significant microbial Fe(III) reduction and high levels of Fe(II) (48 %−100 % of total soluble Fe) may promote the capacity of As methylation. Although no statistical change in Fe phases was observed with low Fe dissolution and high molar Fe/As ratios, higher As bioaccessibility of colon phase (avg. 29.4 %) was mainly contributed from reductive dissolution of As(V)-bearing Fe(III) (oxy)hydroxides. Our results suggest that As mobility and biotransformation by human gut microbiota (carrying arrA and arsC genes) are strongly controlled by microbial Fe(III) reduction coupled with soil particle size. This will expand our knowledge on oral bioavailability of soil As and health risks from exposure to contaminated soils.

Sulfurized nano zero-valent iron prepared via different methods: Effect of stability and types of surface corrosion products on removal of 2,4,6-trichlorophenol

Sulfurization improves the stability and activity of nano zero-valent iron (nZVI). The sulfurized nZVI (S-nZVI) were prepared with ball milling, vacuum chemical vapor deposition (CVD) and liquid-phase reduction techniques and the corresponding products were the mixture of FeS2 and nZVI (nZVI/FeS2), well-defined core-shell structure (FeSx@Fe) or seriously oxidized (S-nZVI(aq)), respectively. All these materials were applied to eliminate 2,4,6-trichlorophenol (TCP) from water. The removal of TCP was irrelevant with the structure of S-nZVI. Both nZVI/FeS2 and FeSx@Fe showed remarkable performance for the degradation of TCP. S-nZVI(aq) possessed poor mineralization efficiency to TCP due to its bad crystallinity degree and severe leaching of Fe ions, which retarded the affinity of TCP. Desorption and quenching experiments suggested that TCP removal by nZVI and S-nZVI was based on surface adsorption and subsequent direct reduction by Fe0, oxidation by in-situ produced ROS and polymerization on the surface of these materials. In the reaction process, the corrosion products of these materials transformed into crystalline Fe3O4 and α/β-FeOOH, which enhanced the stability of nZVI and S-nZVI materials and was conductive to the electron transferring from Fe0 to TCP and strong affinity of TCP onto Fe or FeSx phases. All these were contributed to high performance of nZVI and sulfurized nZVI in removal and minerazilation of TCP in continuous recycle test.

Sources, transport, and deposition of metal(loid)s recorded by sulfide and rock geochemistry: constraints from a vertical profile through the epithermal Profitis Ilias Au prospect, Milos Island, Greece

Drill core samples from the Profitis Ilias Pb-Zn-Cu-Ag-Au vein mineralization on Milos Island, Greece provide new insights into (i) the metal sources, (ii) the primary vertical metal(loid) distribution, and (iii) the supergene enrichment processes in a transitional shallow-marine to subaerial hydrothermal environment. Metal contents of unaltered and altered host rocks combined with Pb isotope analyses of hydrothermal sulfides suggest that most metal(loid)s were derived by leaching of basement rocks, whereas the distinct enrichment of Te is related to the addition of Te by a magmatic fluid. The trace element contents of base metal sulfides record decreasing Au, Te, Se, and Co, but increasing Ag, Sb, and Tl concentrations with increasing elevation that can be related to progressive cooling and fluid boiling during the hypogene stage. The formation of base metal veins with porous pyrite hosting hessite inclusions at ~ 400 m below the surface was triggered by vigorous fluid boiling. By contrast, the enrichment of native Au associated with oxidized Fe and Cu phases in the shallower part of the hydrothermal system resulted from supergene remobilization of trace Au by oxidizing meteoric water after tectonic exhumation to subaerial levels. Disseminated pyrite with higher Tl/Pb ratios and locally elevated Hg concentrations relative to vein pyrite reflects infiltration of the host rocks by boiled liquids and condensed vapor fluids. The vertical and temporal evolution of the Profitis Ilias mineralization, therefore, provides unique insights into the transport and precipitation of Au, Ag, Te, and related metal(loid)s by multiple fluid processes.

Fe(III) Biomineralization in the Surface Microlayer of Acid Mine Waters Catalyzed by Neustonic Fe(II)-Oxidizing Microorganisms

The formation of thin mineral films or encrustations floating on the water surface of low-flow or stagnant zones of acid mine drainage (AMD)-affected streams is probably among the most exotic features that can be found in mining areas. However, most fundamental questions about their origin (biotic vs. abiotic), structure, mineralogy, physical stability and metal-retention capacity remain unanswered. This study aims to reveal the factors promoting their formation and to clarify their composition in detail. With this purpose, the major mineral phases were studied with XRD in surface film samples found in different mine sites of the Iberian Pyrite Belt mining district (SW Spain), and the major oxide and trace metal concentrations were measured with XRF and/or ICP-MS. Fe(III) minerals dominated these formations, with mineralogy controlled by the pH (jarosite at pH~2.0, schwertmannite at pH 2.5–3.5, ferrihydrite at pH &gt; 6.0). Other minerals have also been identified in minor proportions, such as brushite or khademite. These mineral formations show an astounding capacity to concentrate, by orders of magnitude (×102 to ×105), many different trace metals present in the underlying aqueous solutions, either as anionic complexes (e.g., U, Th, As, Cr, V, Sb, P) or as divalent metal cations (e.g., Cu, Zn, Cd, Pb). These floating mineral films are usually formed in Fe(II)-rich acidic waters, so their formation necessarily implies the oxidation of Fe(II) to Fe(III) phases. The potential involvement of Fe(II)-oxidizing microorganisms was investigated through 16S rRNA gene amplicon sequencing of water underneath the Fe(III)-rich floating mineral films. The sequenced reads were dominated by Ferrovum (51.7 ± 0.3%), Acidithiobacillus (18.5 ± 0.9%) and Leptospirillum (3.3 ± 0.1%), three well-known Fe(II)-oxidizing genera. These microorganisms are major contributors to the formation of the ferric mineral films, although other genera most likely also play a role in aspects such as Fe(III) sequestration, nucleation or mineral growth. The floating mineral films found in stagnant acidic mine waters represent hotspots of biosphere/hydrosphere/atmosphere interactions of great value for the study of iron biogeochemistry in redox boundaries.

Mineral characteristics of volcanic ash‐derived soils affecting boron adsorption

AbstractVolcanic ash‐derived soils are naturally deficient in the essential micronutrient B, but they also have maximum adsorption capacities (bB) that are as much as 40 times greater than in nonvolcanic soils, further exacerbating B availability. Because short‐range‐order (SRO) aluminosilicates (allophane and imogolite) and iron (Fe) oxyhydroxides are the main clay‐sized minerals in these soils, we hypothesized that their relative abundances would explain variations in boron sorption capacity (bB). We characterized 23 volcanic ash‐derived soils (Andisols and non‐Andisols) from the Pacific coastal plain of Guatemala by X‐ray diffraction, oxalate and pyrophosphate extractions, and thermal analysis, with four selected soils further examined by Mössbauer spectroscopy (MBS). Only soils with andic character (high SRO Si–Al content) contained considerable amounts of imogolite, with allophane in the clay fraction. Overall, soil SRO Al–Si phases were strongly correlated with clay B adsorption capacity (R = 0.65, p &lt; 0.001) and clay specific surface area (R = 0.88, p &lt; 0.001) suggesting that SRO Al–Si phases are the dominate influence on B behavior in these soils. Fe mineral composition was dominated (39%–71% of total Fe) by SRO Fe(III) oxyhydroxides (nanogoethite and ferrihydrite) of various crystallinities. In low allophane soils, SRO Fe phase abundance correlated with bB as did the abundance of low crystallinity kaolinite phases, suggesting these phases are important when SRO Si–Al content is low. Any efforts to predict B behavior or plan soil fertility treatments in volcanic‐influenced soils needs to consider the impact of SRO phases.

Microstructures, tensile properties, and strengthening mechanisms of novel Al-Mg alloys with high Mg content

This study investigated the microstructures, mechanical properties, tensile deformations, and strengthening mechanisms of the Al-7-mass%-Mg (7Mg) and Al-9-mass%-Mg (9Mg) alloys developed from the Mg+Al2Ca master alloy. The microstructures of both as-extruded alloys comprised an Al matrix and eutectic Mg2Al3, Al2Ca (C15), and Al6(Mn,Fe) phases. The 7Mg alloy mainly consisted of elongated grains surrounded by small equiaxed grains, whereas the 9Mg alloy contained only fine equiaxed grains. Higher Mg content resulted in higher fractions of evenly distributed C15 phases. Tensile tests revealed yield strengths and maximum-tensile strengths of 234 and 429 MPa, respectively, for the 7Mg alloy, and these values increased to 276 and 479 MPa, respectively, for 9% Mg content. The characteristic serrated flow in the 7Mg alloy started at approximately 10% of the engineering strain. In contrast, in the 9Mg alloy, the development of the serrated flow from the beginning of tensile deformation, immediately after the yield point, is considered to be facilitated by the fine equiaxed grains and higher Mg content and number densities of obstacles (owing to the formation of secondary phases). Solid-solution and grain-boundary strengthening mainly contributed to the overall yield strength of the aluminum-magnesium (Al-Mg)-based alloys. Three microstructural factors, higher Mg solid solubility, smaller grain size, and a higher fraction of secondary phases, were responsible for the higher yield strength of the alloy with higher Mg content. Theoretical calculations based on conventional strength-prediction models predicted yield-strength values almost identical to those obtained experimentally, demonstrating the potential of the conventional models to accurately predict the yield strengths of Al-Mg alloys with high Mg content.

Formation mechanism of refined Al6(Mn, Fe) phase particles during continuous rheo-extrusion and its contribution to tensile properties in Al–Mg–Mn–Fe alloys

Tailoring the size and morphology of Al6(Mn, Fe) phase particles is expected to achieve a good combination of strength and ductility in Al–Mg–Mn–Fe alloys. In this study, the microstructural evolution in an Al–5Mg–0.8Mn–0.1Fe (wt%) alloy fabricated through continuous rheo-extrusion was investigated via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation mechanism of the Al6(Mn, Fe) phase particles during continuous rheo-extrusion was revealed. The contribution of the Al6(Mn, Fe) phase particles to the tensile properties of the alloy was discussed. The results indicated that a remarkable refinement effect on the Al6(Mn, Fe) phase particles during continuous rheo-extrusion was achieved. The formation of refined Al6(Mn, Fe) phase particles was primarily attributed to the coefficient of the high cooling rate and shear deformation during continuous rheo-extrusion. Compared with the as-cast alloy containing micron-sized phase particles, the rheo-extruded alloy with nanoscale Al6(Mn, Fe) phase particles exhibited a significant enhancement in strength. During tensile deformation, the small circular cracks around the nano-sized Al6(Mn, Fe) phase particles prolonged the crack propagation time. Hence, a good ductility was obtained in the rheo-extruded alloy. The purpose of this study is to provide a strategy to achieve a high-efficiency processing method and provide insights for manufacturing Al–Mg series alloys with high mechanical performance.

Continuous cultivation of the lithoautotrophic nitrate-reducing Fe(II)-oxidizing culture KS in a chemostat bioreactor.

Laboratory-based studies on microbial Fe(II) oxidation are commonly performed for 5-10 days in small volumes with high substrate concentrations, resulting in geochemical gradients and volumetric effects caused by sampling. We used a chemostat to enable uninterrupted supply of medium and investigated autotrophic nitrate-reducing Fe(II)-oxidizing culture KS for 24 days. We analysed Fe- and N-speciation, cell-mineral associations, and the identity of minerals. Results were compared to batch systems (50 and 700 mL-static/shaken). The Fe(II) oxidation rate was highest in the chemostat with 7.57 mM Fe(II) d-1 , while the extent of oxidation was similar to the other experimental setups (average oxidation of 92% of all Fe(II)). Short-range ordered Fe(III) phases, presumably ferrihydrite, precipitated and later goethite was detected in the chemostat. The 1 mM solid phase Fe(II) remained in the chemostat, up to 15 μM of reactive nitrite was measured, and 42% of visualized cells were partially or completely mineral-encrusted, likely caused by abiotic oxidation of Fe(II) by nitrite. Despite (partial) encrustation, cells were still viable. Our results show that even with similar oxidation rates as in batch cultures, cultivating Fe(II)-oxidizing microorganisms under continuous conditions reveals the importance of reactive nitrogen intermediates on Fe(II) oxidation, mineral formation and cell-mineral interactions.

Temperature effects on the performance of ferroelectric FET with random grain phase variation for non-volatile memory application

We report the temperature effects on the performance of ferroelectric field-effect transistor (FeFET)-based non-volatile memory (NVM) considering random grain phase variation in the ferroelectric layer through simulation. Based on the FE temperature effect model that accounts for both the transistor and ferroelectric degradation, we demonstrate that: (1) at a certain temperature, the memory window (MW) decreases with pronounced effect on low threshold voltage shift and its variation increases as the FE phase decreases; (2) with the temperature increases, the MW decreases with pronounced effect on high threshold voltage shift. The random grain phase variation further exacerbates the MW distribution, thus degrading the sensing margin. These results may provide insights for device design of high-performance FeFET-based NVMs.

Investigation on Solidification in Cu-20wt%Fe Alloy through In Situ Observation

The performance of Cu-Fe alloy is related to the solidification structure, which is directly determined by the microstructure evolution during solidification. The solidification sequence, solid–liquid interface variation, and microstructural evolution of Cu-20wt%Fe alloy at three cooling rates (0.3, 1.5, and 5.0 °C/s) were investigated. The results indicate that the remelting of primary γ-Fe dendrites was directly observed through the solidification experiment, and the partial γ-Fe dendrite was fragmented owing to remelting. The Fe phase morphology changed from the cellular structure to the typical finer and longer dendrite structure with the cooling rate increasing. As the cooling rate increased, the constitutional undercooling caused by the decrease in the Fe atom concentration and the increase in the Cu atom concentration increased in the solidifying interface. There was a parabolic relationship between the growth rate of the dendrite tip and time. Meanwhile, the growth of the primary γ-Fe phase was inhibited by the insufficient diffusion of Fe and Cu at the solidification front, which resulted in a decrease in the Fe phase volume fraction, and the Fe content in the Fe dendritic phase decreased slightly.

Temperature influence on NiFeMo nanoparticles magnetic properties and their viability in biomedical applications.

NiFeMo alloy nanoparticles were synthesized by co-precipitation in the presence of organic additives. Nanoparticles thermal evolution shows that there is a significant increase in the average size (from 28 to 60 nm), consolidating a crystalline structure of the same type as the Ni3 Fe phase but with lattice parameter a=0.362 nm. Measurements of magnetic properties follow this morphological and structural evolution increasing saturation magnetization (Ms) by 578% and reducing remanence magnetization (Mr) by 29%. Cell viability assays on as-synthesized revealed that nanoparticles (NPs) are not cytotoxic up to a concentration of 0.4μg/mL for both non-tumorigenic (fibroblasts and macrophages) and tumor cells (melanoma).

Residual stress mitigation in directed energy deposition

Directed Energy Deposition (DED), a class of additive manufacturing techniques, has seen rapid growth over the last decade for potential applications in aerospace, medical devices, and energy systems. Despite notable progress in the research and development of AM, control and mitigation of residual stress during DED remains a challenge. In this work, we propose a novel approach that can be used for the mitigation of residual stresses in additively manufactured components. Specifically, we propose to mitigate the residual stress state of as-deposited components using alloy design, engineering of solid-state transformations, and the introduction of both hard and soft metallic phases. We demonstrate this strategy with a model system consisting of pure Fe and Fe–Cu. Experimental results indicate that residual stresses can be successfully manipulated by adjusting the alloy composition as a soft metallic phase can accommodate plastic deformation. Moreover, our findings suggest that the solid-state transformations experienced by the Fe and Fe-rich phases contribute to the observed differences in magnitude and location of residual stresses. This study is the first to suggest using residual stress as an engineering criterion in the design of alloys for metal additive manufacturing.

Study on Mechanism of Titanium Slag Smelting in DC electric Arc Furnace

Based on the production practice of a 30MWA large DC electric furnace in Yunnan, this paper discusses the basic reactions in smelting titanium slag, and discusses the thermodynamic and kinetic behaviors of the main elements and impurities. The results show that the reduction reaction in the smelting process is carried out simultaneously in the multi-component system of Al2O3-CaO-MgO-SiO2-TiO2. The titanium slag containing more than 80% TiO2 can be obtained by enrichment smelting of ilmenite in a large high-power enclosed direct current electric arc furnace, and the output includes by-product pig iron. Impurities MgO, CaO and Al2O3 in titanium concentrate will not be reduced during reduction smelting; SiO2, MnO and V2O5 will be reduced in varying degrees, and the reduced products Si, Mn and V will dissolve in the metal Fe phase or be enriched in titanium slag.