Fe-Cu Alloys Research Articles

Microstructure and properties of cold-drawn Cu and Cu-Fe alloy wires

Copper and Cu-Fe alloy wires were cold drawn at room temperature, and the microstructure and properties were characterized and analyzed. The results show that, at the same drawing strain, the strength and ductility of Cu-Fe wires are higher than those of copper wires. At a drawing strain of 4, the tensile elongation of Cu-Fe alloy wires is about 5%, much higher than 2% for pure copper wires. For Cu-Fe wires, with increasing drawing strain, the Fe phase is elongated along the drawing direction and forms a fiber structure with a <110> texture. In addition to the <111> and <100> fiber textures in the copper wire, a high-intensity of texture with a <112> orientation forms in Cu-Fe alloy wires. The ductility of the Cu-Fe alloy wires is greatly preserved due to dynamic recrystallization. Moreover, with the additional refining effect of nano-copper fibers in the Fe phase, the strength of the material is greatly improved.

Design of high strength Fe–C–Cu alloys for laser powder bed fusion

Two Co- and Ni-free high strength steel alloys from the Fe–C–Cu system, Fe-0.2C–6Cu wt.% (FeCu) and Fe-0.2C-3.5Cu-0.2Si–1Mo–1Cr-0.2 V wt. % (FeCu+), were designed and evaluated for use in laser powder bed fusion (LPBF) printing for non-stainless automotive applications. A computational materials design approach combined with melt-spinning was employed to design Co- and Ni-free printable compositions. Custom gas atomized powders were acquired and characterized for chemistry, contaminants, defects, and particle size distribution. Parameter development was performed on a Renishaw AM250 to obtain specimens with consolidation greater than 99.8% density. Single step heat treatment studies determined peak hardnesses of 426 VHN for the FeCu alloy and 435 VHN for the FeCu+ alloy. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) revealed the heat-treated microstructure to be lath martensite with 2.6–2.8 nm diameter Cu precipitates, within the same diameter range as previously reported for BCC Cu strengthening in other steels. Tensile tests demonstrated yield strengths of 1208 MPa for the FeCu alloy and 1274 MPa for the FeCu+ alloy. Process-induced porosity and lack-of-fusion defects were observed on the fracture surfaces of the printed tensile specimens. With further parameter optimization, these alloys have the potential to be a low-cost, high-strength steel option for use in metal 3D printing for automotive applications.

Influence of elasticity on the morphology of fcc-Cu precipitates in Fe-Cu alloys. A phase-field study

Cu-rich precipitation ensures high strength and satisfactory ductility of steels at low carbon content. Although in an over-aged state, it leads to the degradation of mechanical properties. It is of prime importance for nuclear reactor vessel steels, which are exposed to extreme conditions at elevated temperature for a long time. The precipitates at this state have an fcc structure and possess a characteristic elongated morphology. The invariant-line model was mostly used to explain the morphology of fcc-Cu precipitates in the bcc-Fe matrix, although it has several limitations. It idealizes morphology and does not consider the elastic properties of both precipitate and matrix. Also, this method does not reveal the influence of the eigenstrains on kinetics and the formation of the nanostructure. Besides, the influence of the applied stress on the precipitation process can’t be revealed with this method.With this in mind, we developed a phase-field model to investigate the formation of the elongated morphology of fcc-Cu precipitates in the bcc-Fe matrix. The effect of diffuse interface and discretization on the behavior of solution was verified with a sharp-interface model and invariant-line prediction. It was found that simulated precipitates agree qualitatively with available experimental data. The role of a minimal mismatch line on the morphology formation was verified. Also, it was shown that the anisotropy of elastic properties has a minor effect on morphology formation. The applied stress with different magnitudes and directions has a minor effect on the morphology of precipitates. Nevertheless, it results in variant selection due to the difference in interaction energy. The bifurcation diagram of interaction of two precipitates was constructed. The equilibrium configurations reveal that elasticity enhances the kinetics of the reaction and that there is a twin-like configuration, which enhances the accommodation of shear-like eigenstrain and reduces the elastic interaction energy.

Phase Transitions of Cu and Fe at Multiscales in an Additively Manufactured Cu-Fe Alloy under High-Pressure.

A state of the art, custom-built direct-metal deposition (DMD)-based additive manufacturing (AM) system at the University of Michigan was used to manufacture 50Cu–50Fe alloy with tailored properties for use in high strain/deformation environments. Subsequently, we performed preliminary high-pressure compression experiments to investigate the structural stability and deformation of this material. Our work shows that the alpha (BCC) phase of Fe is stable up to ~16 GPa before reversibly transforming to HCP, which is at least a few GPa higher than pure bulk Fe material. Furthermore, we observed evidence of a transition of Cu nano-precipitates in Fe from the well-known FCC structure to a metastable BCC phase, which has only been predicted via density functional calculations. Finally, the metastable FCC Fe nano-precipitates within the Cu grains show a modulated nano-twinned structure induced by high-pressure deformation. The results from this work demonstrate the opportunity in AM application for tailored functional materials and extreme stress/deformation applications.

The interaction mechanisms between dislocations and nano-precipitates in CuFe alloys: A molecular dynamic simulation

Molecular dynamics (MD) simulations are employed to study the interaction mechanisms between dislocations and nano-precipitates in CuFe alloys. On one hand, the critical shear stress to activate nucleation of dislocations around α-Fe nano-precipitates is substantially reduced, which promotes twinning deformation and dislocation gliding away from the nano-precipitates. On the other hand, nano-precipitates could also prevent dislocations from moving towards themselves. A hybrid model is developed to demonstrate the strengthening behaviors with an enhancing efficiency factor (β) introduced. Large α-Fe nano-precipitates lead to high strengthening efficiency, but an optimized size is obtained owing to the softening effect of large nano-precipitates. Moreover, the strengthening effects of nano-precipitates will disappear if the loading speed exceeds a critical value.

High Strength and High Electrical Conductivity in Cu-Fe Alloys with Nano and Micro Fe Particles

High Strength and High Electrical Conductivity in Cu-Fe Alloys with Nano and Micro Fe Particles

Density and molar volumes of liquid alloys of iron with C, B, Si, P, Cu, Al, Ni, Cr and Mn

The paper discusses density and molar volume of liquid alloys of iron with C, B, Si, P, Cu, Al, Ni, Cr and Mn. Liquid alloys of iron with other metals are considered as substitutional solutions using the hard-sphere model. Deviations of molar volumes of Fe-Cu and Fe-Al alloys from the ideal solutions were analysed using relationship between excess volume and entropy. Alloys of iron with Ni, Cr and Mn are close to the ideal solutions. Calculated volumes are in agreement with experimental data. Alloys of Fe with C, B, Si and P are considered as interstitial solutions using P. Gaskell�s model developed for amorphous alloys of transition metals with metalloids. Calculated partial molar volumes of C, B, Si and P in dilute binary solutions at 1823 K are (cm3/mol): 1.59, 3.37, 7.06 and 6.26 respectively. The model correctly describes the liquid alloys of iron with metalloids as interstitial solutions.

Numerical Investigation for Measuring Interfacial Tension of Undercooled CuFe Alloy by an Oscillating Droplet Method in the International Space Station

Numerical Investigation for Measuring Interfacial Tension of Undercooled CuFe Alloy by an Oscillating Droplet Method in the International Space Station

Verification of Possibility of Molten Steels Decopperization with ZnAl2O4

In the previous research works, ZnAl2O4 material was considered as one of the solutions for the decopperization process of molten steels; up to 33% of decopperization efficiency was reported by utilising the ZnAl2O4 filter. In order to verify the decopperization possibility of ZnAl2O4 materials, iron-based alloys with various copper and carbon contents were interacted with ZnAl2O4 substrates in a heating microscope under an argon gas atmosphere at 1600 °C. Fe-Cu alloys were found to react with the ZnAl2O4 substrate during the interaction process, and a reaction layer with a complex composition around the alloy droplet was formed; however, Cu was not detected in the reaction layer. Cu was later found infiltrated inside of the ZnAl2O4 substrates. Furthermore, the Cu-Zn compounds were detected when the copper content in Fe-Cu alloys was 10 wt% Cu. After interaction experiments, copper was decreased in all cases. Thereby, the copper evaporation and infiltration into the ZnAl2O4 substrate were considered as the reasons for copper loss. Moreover, oxygen dissolved in melt was found to have a great effect on the copper evaporation process.

The study of microhardness of powder metallurgy fabricated Fe-Cu alloy using vickers indenter

In the present study, micro hardness values of Iron-Copper based alloys with different compositions have been obtained by using Vickers indenter. The samples Fe-5Cu-1Sn-7.5BN (wt. %), Fe-5Cu-1.5Sn-5BN (wt. %) and Fe-5Cu-2.5Sn-2.5BN(wt. %) were prepared using Powder metallurgy technique. The elemental powder mixture was mixed for 2 hours, and compacted at a pressure of 500Mpa, and then was sintered in dry hydrogen atmosphere at a temperature of 9000C for 50 minutes time. Vickers hardness values were obtained under the loads of 0.01 kg to 0.3 kg. The material with 2.5 wt. % of Sn exhibited the highest value of the hardness. The material with higher hardness shows better mechanical and tribological properties and can be used for various applications such as gears, bearings, connecting rods cams etc. Copyright © 2017 VBRI Press.

Irradiation and thermal effects on the mechanical properties and solute cluster evolution of Fe-Cu alloy

Fe-1.3at.% Cu alloys were irradiated at 563 K and 773 K to explore the irradiation and thermal effects on the mechanical properties and solute cluster evolution of Fe-Cu alloy. Nanoindentation and atom probe tomography were performed to characterize the hardness and distribution of the solute atoms. The results show that hardness of the alloy increases after irradiation at both temperatures and higher hardness increment is observed at 773 K. Cu clusters with a high number density are formed after irradiation. The volume fraction of the clusters increases from about 0.70% at 563 K to 2.80% at 773 K. These clusters contribute to the hardening of the irradiated alloys. Upon comparing the size and number density of these clusters at different temperatures with different doses of 0, 0.018 and 0.18 dpa, it’s found that although both irradiation and thermal effects enhance the precipitation of Cu atoms from the matrix, they have an opposite effect on the evolution of Cu clusters: thermal effect enhances the growth of stable Cu clusters, whereas irradiation primarily promotes the nucleation of the Cu clusters and decomposes the larger Cu clusters.

Hierarchical microstructure and strengthening mechanism of Cu-36.8Fe alloy manufactured by selective laser melting

A near-full dense Cu-36.8Fe alloy was manufactured by selective laser melting (SLM). The as-SLMed Cu-Fe alloy exhibits an excellent combination of both high strength and superior ductility. The exceptional mechanical performances are associated with the unique hierarchical microstructures, including molten pools, sub-micron cellular bi-phasic structures and nano-scaled precipitates. The formation of hierarchical microstructures is presumably owing to rapid cooling rate of molten pool, repeat heating during SLM and intrinsically immiscible feature between Cu and Fe. These findings can provide insights for the application of SLM technique to other immiscible alloys and their design with higher mechanical performances.

Laser powder bed fusion of ultrahigh strength Fe-Cu alloys using elemental powders

Laser powder bed fusion (LPBF) was employed to produce Fe and Fe-(10–50 vol%) Cu immiscible alloys using elemental powders. The addition of 10 vol% Cu to Fe resulted in ultrahigh compressive yield and ultimate strengths of >~ 1000 and ~ 1400 MPa (more than 2 times greater than those in LPBF Fe and 4–6 times than in conventionally processed Fe), respectively, with fracture strain of ~ 20%. However, a further increase in the amount of Cu gave rise to significantly more heterogeneous microstructures with non-uniform distribution of Cu, leading to considerable liquation cracking, large voids and reduced strength and plasticity. Strengthening was primarily attributable to the dispersion of nano-Cu particles of 2–5 nm with spacings of < 10 nm and ultrafine grains (<~ 50–300 nm). The substantial grain refinement in Fe-Cu alloys during LPBF was mainly a result of the confinement of Fe crystals by Cu films, hindering their growth. By analysing microstructures in single laser tracks, single layers, top and middle sections of the LPBF Fe, it was revealed that constitutional undercooling during solidification or the subsequent transformations of γ → α were responsible for the formation of equiaxed, rather than columnar, grains in pure Fe.

Influence of Fe Addition on the Microstructure and Mechanical Properties of Cu Alloys

The influence of Fe addition on the microstructure and mechanical properties of Cu alloys was studied. Combined with phase identification via EDS, X-ray diffraction shows that only Cu matrix and α-Fe phase exist in Cu-5Fe, Cu-10Fe and Cu14Fe alloys. With the addition of Fe, the grain size refines from 1011 μm in pure Cu to around 46 μm in Cu-Fe alloys. Phase identification of the alloys via EBSD shows that the α-Fe phase with an average grain size of about 4 μm is ocated in grain boundaries and in the grain interior.

CO2 Hydrogenation to Olefin-Rich Hydrocarbons Over Fe-Cu Bimetallic Catalysts: An Investigation of Fe-Cu Interaction and Surface Species

Previously, we reported a strong Fe-Cu synergy in CO2 hydrogenation to olefin-rich C2+ hydrocarbons over the γ-Al2O3 supported bimetallic Fe-Cu catalysts. In this work, we aimed to clarify such a synergy by investigating the catalyst structure, Fe-Cu interaction, and catalyst surface properties through a series of characterizations. H2-TPR results showed that the addition of Cu made both Fe and Cu easier to reduce via the strong interaction between Fe and Cu. It was further confirmed by X-ray absorption spectroscopy (XAS) and TEM, which showed the presence of metallic Fe and Fe-Cu alloy phases in the reduced Fe-Cu(0.17) catalyst induced by Cu addition. By correlating TPD results with the reaction performance, we found that the addition of Cu enhanced both the moderately and strongly adsorbed H2 and CO2 species, consequently enhanced CO2 conversion and C2+ selectivity. Adding K increased the adsorbed-CO2/adsorbed-H2 ratio by greatly enhancing the moderately and strongly adsorbed CO2 and slightly suppressing the moderately and strongly adsorbed H2, resulting in a significantly increased O/P ratio in the produced hydrocarbons. The product distribution analysis and in situ DRIFTS suggested that CO2 hydrogenation over the Fe-Cu catalyst involved both an indirect route with CO as the primary product and a direct route to higher hydrocarbons.

Investigation of Cu heteroatoms and Cu clusters in Fe-Cu alloy and their special effect mechanisms on the Fenton-like catalytic activity and reusability

Fe/Cu bimetallic materials are promising Fenton-like catalysts to deal with the increasing environmental pollution. However, it remains a great challenge to prepare conveniently desirable Fe/Cu co-catalysts with brilliant catalytic efficiency and simultaneously reveal their co-catalytic mechanism. Herein, we report a facile approach of generating Fe-Cu alloys with outstanding Fenton-like catalytic performance via a straightforward electrodeposition method. The degradation ability of Fe-Cu alloy mainly comes from Fe2+/H2O2 reaction, while the Cu components including the Cu heteroatoms in Fe lattice and the independent Cu clusters in alloy play a notable assistant role. Experiments and density functional theory (DFT) calculations indicate that the Cu heteroatoms enhance the capacity of adjacent Fe atoms for the adsorption of H2O2 to generate more •OH, while the independent Cu clusters suppress the surface passivation of catalyst for improving the reusability in cycle experiments. Our study will promote the industrial application of bimetallic Fenton-like catalysts for water treatment.

Effect of Zr addition on metastable Liquid-Liquid Phase Separation of Cu-Fe alloys

The liquid-liquid phase separation (LLPS) behavior was investigated in Cu-Fe alloys that consisted of 60 wt % or 80 wt % Cu and balance iron, without or with addition of 1 wt% Zr. Both Zr-free alloys clearly showed LLPS at metastable spinodal temperatures prior to γ-Fe nucleation, whereas Zr-added showed γ-Fe phase evolution without LLPS. Addition of Zr was highly effective to activate γ-Fe nucleation by decreasing the mixing enthalpy and also accelerating heterogeneous nucleation. A combination of thermal instrumental analysis and classical nucleation theory yielded an effective assessment made of LLPS behavior below the liquidus temperature of Cu-Fe alloys. Furthermore, it was possible to control the solidification mechanism of Cu-Fe alloy by zirconium addition.

Microstructure evolution and magnetic properties of metastable immiscible Cu-Fe alloy with micro-alloying B element

In the present study, metastable immiscible Cu-20Fe-xB alloys with different B addition content were systematically investigated. Experimental results demonstrated that the introduction of micro-alloying B element results in significant change in the solidification microstructure. It was found the volume fraction of phase-separated Fe-rich spherulite increases with increasing B addition content accompanied with an increase in the average size, which experimentally confirms that the liquid-liquid phase separation is further enhanced as B addition increases. In addition, statistical result on scaled size distribution of the phase-separated Fe-rich spherulite indicated that both the concentrated location for the first and second peak are shifted to a larger size scale with increasing B addition. Phase diagram calculation confirms that a stable miscibility gap comes into being by introducing B element, and the length of miscibility gap for Cu-20Fe alloy is obviously enlarged with increasing B addition amount. This should be responsible for such above-mentioned experimental results. Besides, the magnetic properties of Cu-20Fe alloy can be obviously enhanced with B addition. For Cu-20Fe-0.3B alloy, the saturated magnetization is 41.74 emu/g, which is 32.3% significantly higher than that of the original Cu-20Fe alloy (31.56 emu/g). It is anticipated that the present study provides a feasible method by tailoring the micro-alloying B content for immiscible Cu-Fe alloy thus offering desired magnetic properties.

Atomic scale insights into the rapid crystallization and precipitation behaviors in FeCu binary alloys

Molecular dynamics (MD) simulations are employed to probe the crystallization and precipitation behaviors in FeCu alloys. The alloys will undergo liquid phase separation at high temperature, after which α-Fe nucleates preferentially, then metastable Cu solid solutions in BCC lattice (ε` phase) nucleate and transform into FCC structure (ε-Cu) via martensite phase transformation immediately. Reversible order-disorder transformation behavior is observed during time-consuming crystallization process of ε-Cu. Interestingly, the ε`-Cu with only approximately three atomic layers in thickness exists stably near BCC/FCC α/ε interface at room temperature, following the Kurdjumov–Sachs (K–S) orientation relationship. The lower nucleation energy and interface energy are the reasons for the existence of abnormal ε`-Cu at the interface. It is also found that the composition and cooling rate play key roles on the final phase structure. The alloys can be fully crystallized upon cooling down at a rate of 0.1 K/ps.

Fe-Cu Alloy-Based Flexible Electrodes from Ethaline Ionic Liquid

The effective implementation of energy storage systems within flexible structures has recently become of particular interest. Here, the fabrication of inexpensive flexible electrodes via a number of straightforward methods formed the motivation for this research. Thin film-based Fe-Cu alloys were cathodically electrodeposited on a graphite substrate. As ionic liquids consist purely of ions (not solvent), they have recently been used in some electrochemical applications. In this study, therefore, Fe-Cu alloy coatings were prepared from an ethaline ionic liquid containing iron and copper salts. The electrochemical behaviour of Fe-Cu alloy films was determined by scanning between − 1.0 V and − 0.3 V in 1 M KOH at various scan rates ranging from 5 mV s−1 to 200 mV s−1. These films were characterised in terms of their structural and morphological properties by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and x-ray diffraction (XRD). Formation of iron and copper alloy was differentiated depending on applied potential. The supercapacitive ability of Fe-Cu-coated film observed in 1 M KOH electrolyte demonstrated a specific capacitance of 304 F g−1 at a scan rate of 5 mV s-1. The reaction between the alloy and the electrolyte was mainly controlled by a surface-controlled reaction. An asymmetric supercapacitor was constructed with an Fe-Cu-coated graphite negative electrode and a non-woven graphite positive electrode. Four asymmetric supercapacitors were connected in series and used to light up a blue light-emitting diode. This study shows that ethaline ionic liquid is a promising medium for the preparation of alloy-based electrodes in energy storage applications.