Intermetallic Research Articles

Electron Beam Welding of Copper and Aluminum Alloy with Magnetron Sputtered Titanium Filler

In this work, the results from the electron beam welding of copper and Al6082T6 aluminum alloy with a titanium filler are presented. The influence of the filler on the structure and mechanical properties of the welded joint is studied in comparison with one without filler. The X-ray diffraction (XRD) method was used to obtain the phase composition of the welded joints. Scanning electron microscopy (SEM) was used for the study of the microstructure of the welds. Energy-dispersive X-ray spectroscopy (EDX) was applied to investigate the chemical composition. The mechanical properties were studied by means of microhardness measurements and tensile tests. A three-phase structure was obtained in the fusion zone consisting of an aluminum matrix, an intermetallic compound CuAl2, and pure copper. The application of Ti filler significantly decreased the amount of molten copper introduced in the molten pool and the number of intermetallic compounds (IMCs). This improved the strength of the joint; however, some quantity of IMCs was still present in the zone of fusion (FZ), which reflected the microhardness of the samples. The application of a titanium filler resulted in refining the electron beam weld’s structure. The finer structure and the reduced amount of the brittle intermetallic phases has led to an increase in the strength of the joint.

Highly effective flame-retardant coatings consisting of urea-formaldehyde resin/aluminium hydroxide/boric acid for polystyrene foam: Properties and mechanisms investigation

The flame-retardant properties of expanded polystyrene (EPS) foam were enhanced by constructing a flame-retardant coating on its surface using melamine modified urea-formaldehyde resin (MUF), H3BO3, and Al(OH)3 as raw materials. A coating consisting of an equal proportion of H3BO3 and Al(OH)3 demonstrated superior mechanical properties, flame-retardant properties, and smoke suppression ability. Additionally, this coating increased the compressive strength of EPS material by 43.30 %, raised the carbon residue from 0.14 % to 32.4 %, elevated the limiting oxygen index to 37.4 %, and achieved a vertical combustion rating of V-0 according to UL-94 standards. These improvements were accompanied by a reduction in peak heat release rate by 59.36 %, total smoke production by 51.99 %, maximum smoke density by 80.13 %, and smoke density rating by 89.52 %. Furthermore, the coated material exhibited satisfactory water resistance, thermal insulation, and transparency. Simulation results show that the MUF/H3BO3/Al(OH)3 coating system generated various metal and non-metal compounds during combustion along with NOx, COx, and H2O gases. The beneficial flame-retardant effect of the coating can be attributed to the hybrid flame-retardant effect of H3BO3 and Al(OH)3 in both the gas and condensed phases.

Transient liquid phase bonding of Hastelloy X to Ni3Al intermetallic compound: Microstructure and phase transformation study

The microstructure of dissimilar transient-liquid-phase (TLP) bonding of Hastelloy X nickel base super alloy to Ni3Al intermetallic by AWS BNi2 filler metal at different temperatures (1000–1150 °C) and time ranges (60–180 min) was investigated. A novel study was done to correlate the phase transformation during bonding with microstructure and phase transformation using field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HR-TEM), and high temperature X-ray diffraction (HTXRD). Efforts were performed to correlate the phase transformation stages during isothermal solidification (IS), formation of Cr-Mo precipitates in diffusion affected zone (DAZ) and dissolution of nickel silicides (eutectic morphology) in athermal solidification zone (ASZ) with their respective reaction temperatures. The high tendency of Hastelloy X to react intensely with filler metal generated Mo-Cr rich phase in DAZ. The ISZ was developed across the joint area after holding at 1100 °C for 180 min. High temperature XRD results on half joint of HX revealed new phases generated at above 1050 °C including BNi2,BNi3, and Ni2Si (Ni-Si eutectic phase) confirmed by FESEM. On the other half joint (Ni3Al), no BNi phases were generated nor nickel silicides by increasing temperature as high as 1150 °C.

Synergistic Anti-Dermatophytic Potential of Nanoparticles and Essential Oils Combinations

AbstractConventional antifungal therapies becoming less effective in treating dermatophytic infections. For this reason, researchers are looking for alternative treatments. The current research has tested the antifungal efficacy of eight novel synthesized metallic nanoparticle compounds: Ag0.49Cr2.51O4, Ag0.99Fe1.01O3, CoLa0.019Fe1.981O4, Co0.99Fe1.99O4, Ag0.99Cr1.01O2, Ca0.99Fe1.99O4, CoBi0.019Fe1.981O4, and Cu0.99Fe1.99O4 were synthesized by a flash auto-combustion reaction to evaluate synergistic potential of the Np’s exhibited antifungal activity in combination with Cinnamon, clove, lemongrass, tea tree and thyme essential oils extracted by soxhlet method against Microsporum canis, Trichophyton tonsurans, T. violaceum, T. verrucosum, and Epidermophyton floccosum. Four nanoparticle compounds exhibited antifungal activity which were: Ag0.49Cr2.51O4, Ag0.99Fe1.01O3, CoLa0.019Fe1.981O4, and Co0.99Fe1.99O4 against all tested dermatophytes. Maximum inhibition was recorded in the cases of Ag0.99Fe1.01O3, Ag0.99Fe1.01O3 + cinnamon against M.canis. Least minimum inhibitory concentrations were attained by Cinnamon against M. canis, Ag0.99Fe1.01O3 against M.canis, T. tonsurans, and T.violaceum, Ag0.99Fe1.01O3+Cinnamon against M. canis, T. violaceum and, T. verrucosum, Ag0.99Fe1.01O3 + Clove, and Ag0.99Fe1.01O3 + Lemongrass against M. canis. The study showed promising results regarding the synergistic antifungal efficacy of nanoparticle compounds combined with essential oils in the cases of Ag0.99Fe1.01O3 with cinnamon, Ag0.99Fe1.01O3 with clove and Ag0.99Fe1.01O3 with lemon grass against all tested dermatophytes.

Construction of polymer-derived double transition metal compound/carbon matrix nanocomposites for efficient electromagnetic wave absorber

As typical dielectric materials, transition metal compounds have a broad potential in the field of stealth, but their application is still hampered by poor conductivity. In this study, based on the mechanism of electrostatic self-assembly of heteropolyacids and organic ligands, the electrostatic structures obtained after the introduction of different heteropolyacids into the conductive phase pyrrole are carbonized. On the one hand, the as-prepared transition metal compounds/carbon matrix nanocomposites produce synergistic effects and optimize impedance matching, and on the other hand, the formation of the abundant heterogeneous interfaces as well as the doping of the N, P heteroatoms induce the generation of interfacial polarisation and dipole polarisation, all of which provide the opportunities to produce composites with enhanced electromagnetic wave absorption properties. Unsurprisingly, the best synthesised sample, Mo2C/W2C/NPC, exhibits a significantly improved electromagnetic wave absorption performance, with an effective bandwidth of 5.7 GHz at a matched thickness of 2.5 mm, where the minimum reflection loss value of −54.5 dB is also achieved. The total effective bandwidth of the Mo2C/W2C/NPC-35 wt% is up to 10.5 GHz (7.3–17.8 GHz) via adjusting the matching thickness in the range of 1.7–3.5 mm. Therefore, this study reflects that dual transition metal compound/carbon based composite wave-absorbing materials provide a new material basis for the construction of high-performance absorption materials.

Combustion and energy performance of multiple aluminum-based alloy particles

The long ignition delay time, high ignition temperature and agglomeration prevent the aluminum (Al) particles from fully releasing the chemical energy stored within them during combustion. Al-based alloy fuels with high energy density and excellent combustion performance have become a potential candidate for replacement with pure Al. Therefore, understanding the combustion and energy performance of Al-based alloys is beneficial for the development of Al-based energetic materials. Herein, the combustion and energy performance of pure Al and three Al-based alloys were comparatively investigated by means of a thermal analysis system, an ignition and combustion test apparatus, and a variety of physicochemical property characterizations. The results showed that all three Al-based alloys contained at least one intermetallic compound. Al-boron (B) and Al-magnesium (Mg)-B alloys had higher theoretical energy densities than pure Al, while Al-Mg did not. The thermal oxidation properties of all three alloys were significantly better than those of pure Al. Compared with pure Al, the three alloys showed higher burning rate, shorter ignition delays, more vigorous combustion, and higher burnout at room pressure in air. This is still true after adding AP. According to the compositions of the condensed combustion products, the possible chemical reactions during the combustion of the alloys were speculated. Grasping the combustion mechanisms of the alloys is challenging due to the relative lack of thermodynamic data on intermetallic compounds. Finally, a comprehensive comparison of the combustion processes of pure Al and alloys was made. Although the Al-Mg alloy does not have the same theoretical energy density as pure Al, the more outstanding combustion performance and fewer two-phase flow losses may make up for the gap in theoretical energy density.

In-situ atomic tracking of intermetallic compound formation during thermal annealing

Intermetallic compounds (IMCs) with ordered atomic structure have gained great attention as nanocatalysts for its enhanced activity and stability. Although the reliance of IMC preparation on high-temperature annealing is well known, a comprehensive understanding of the formation mechanisms of IMCs in this process is currently lacking. Here, we employ aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) to track the formation process of IMCs on carbon supports during in-situ annealing, by taking PtFe as a case study within an industry-relevant impregnation synthesis framework. We directly discern five different stages at the atomic level: initial atomic precursors; Pt cluster formation; Pt-Fe disordered alloying; structurally ordered Pt3Fe formation, and final Pt3Fe-PtFe IMC conversion. In particular, we find that the crucial role of high-temperature annealing resides in facilitating the diffusion of Fe towards Pt, enabling the creation of alloys with the targeted stoichiometric ratio, which in turn provides the thermodynamic driving force for the disorder-to-order transition.

Exploration microstructural evolution and wear mechanisms of wire arc additive manufacturing NiTi/Nb bionic composite materials

NiTi/Nb layered heterogeneous structure (LHS) materials with different layer spacings were designed and fabricated using composite wire arc additive manufacturing. The NiTi/Nb LHS samples consisted of NiTi phase and β-Nb phase, and no other intermetallic compounds were formed. The NiTi layer in the NiTi/Nb LHS sample changes from a homogeneous eutectic microstructure to a gradient heterogeneous eutectic microstructure as the layer thickness increases. The Nb layer grains are much smaller than the NiTi layer grains, and no obvious texture is formed in the NiTi/Nb LHS samples. NiTi/Nb LHS samples still have a certain recoverable strain at room temperature, with a maximum recoverable strain of 4.36 % after 10 cycles of 10 % strain compression. The wear rate of the NiTi layer of the NiTi/Nb LHS samples was lower than that of the Nb layer. The main wear mechanisms on the Nb surface are abrasive wear, adhesive and oxidative wear while the main wear mechanism on the NiTi surface is adhesive wear. When the layer thickness ratio of NiTi layer to Nb layer is 2:1, the NiTi/Nb LHS samples form a gradient heterogeneous eutectic structure in the NiTi region, which in turn enhances the wear resistance of the LHS samples. In this study, cross-scale NiTi alloy and Nb heterogeneous components were constructed by wire arc additive manufacturing, which showed good wear resistance. The design provides a new solution for integrated additive manufacturing repair of heterogeneous metals in engineering applications.

Dissimilar impact spot welding of high-thickness aluminum-steel sheets using vaporizing foil actuators

The automotive industry’s shift towards multi-material structures necessitates efficient joining of aluminum and steel, yet techniques for high-thickness (>2 mm) dissimilar AA6XXX-HSLA steel pairs, remain underexplored. This study explores vaporizing foil actuator welding for spot welding 2.5 mm AA6111-HSLA 340 steel pairs, demonstrating successful joint formation via lap-shear testing and microscopy. Post-weld heat treatment influences joint strength and fracture behavior, with intermetallic compound (IMC) formation at the weld interface affecting mechanical properties. IMC cracking is observed in heat-treated samples. Fracture analysis reveals material transfer and secondary brazing action outside the weld zone. VFAW lap-shear failure loads outperform other joining techniques.

Fabrication of Al-Ti intermetallic alloy via aluminothermic reduction process from TiO2 in molten salts

ABSTRACT A novel method based on the aluminothermic reduction of TiO2 in Na3AlF6-AlF3-CaF2 molten salts has been proposed to prepare Al-Ti intermetallic alloys in this research. The Al-Ti intermetallic alloy was obtained by reducing dissolved TiO2 in electrolyte molten salt using liquid Al as a reductant at the stirring rate of 200 r/min for 5 min under 960°C, and it was mainly enriched in the Al matrix which was dispersed in molten salts. The lower alloy layers in the melt pool were characterised by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), taking advantage of the specific gravity difference between the molten salt and the alloy. The TiAl3 was the major intermetallic alloys phase formed between Al and Ti according to XRD results. The Al2O3 by-product in the reduction process of TiO2 was dissolved in electrolyte molten salt.

Trailblazing multi-material structure: Niobium alloy to tungsten–copper composite using wire-arc additive manufacturing

Integrating tungsten and niobium alloys into a single component offers synergistic benefits for fusion reactor applications. Additive manufacturing, particularly for components with complex geometries, further amplifies these advantages. This study examines the fabricability of a multi-material structure composed of a W–Cu composite and an Nb–Zr alloy using wire-arc additive manufacturing. The resulting W–Cu/Nb–Zr structure was free from significant defects like porosity or cracks, though the formation of hard intermetallic compounds was observed. Numerical analysis indicated considerable residual stress accumulation at the interface. During tensile testing, fractures occurred in the W–Cu composite near the interface, with the specimens exhibiting an ultimate tensile strength of 218 ± 3 MPa and an elongation of 5.7 ± 1 %.

Laser lap joining of R60702 zirconium alloy and 304 stainless steel utilizing CoNiTiV high entropy alloy

In this study, the laser lap welding of R60702 zirconium alloy and 304 stainless steel was successfully achieved by incorporating CoNiTiV high entropy alloy (HEA) interlayer. The addition of HEA interlayer altered elemental diffusion and prevented the formation of Zr-Fe intermetallic compounds. The maximum tensile and shear strength of the joint (998.4 N) is 2.5 times that of the sandwich joint without the HEA layer (392.1 N), with the displacement also increasing by 85 %. The inclusion of the intermediate HEA layer transforms the original brittle fracture mode into a tough-brittle mixed fracture mode. The elimination of Zr-Fe intermetallic compounds is the primary factor contributing to the enhancement of mechanical properties. The main phase composition includes α-Zr, Cr2Zr, CoTi2, Ni7Zr2 and Zr3Co phase.

Sabatier principle based design of high performance FeCoNiMnMoP high entropy electrocatalysis for alkaline water splitting

FeCoNi-based high entropy intermetallic compounds are promising substitutes for noble metal catalysts for hydrogen evolution reaction (HER) and oxygen evolution (OER), while their activity is restricted by the synergistic effect between the elements. In this paper, the theoretical model of FeCoNiMnMoP bifunctional catalyst has been reasonably designed given the volcanic curve of M−H bond energy as a valuable guide for candidate metal elements. Theoretical calculations show that the synergistic effect between multiple sites not only accelerates the electron transfer but also reduces the rate-determining step (RDS) barrier. At the same time, the introduction of Mo also enhances the total density of states and reduces the d-band center, thus optimizing the adsorption and dissociation of intermediates. The experimental results confirm that the theoretical model has excellent catalytic performance. In the alkaline solution, FeCoNiMnMoP‖FeCoNiMnMoP requires only an ultra-low cell voltage of 1.49 V for overall water splitting when the current density is 10 mA cm−2. In general, novel insights on the effects of intermetallic synergies on water decomposition are provided, which is helpful for the design of bifunctional catalysts based on volcanic diagrams.

Crystal structure re-determination of binary IrAl2.75 into Ir8Al21.22

The Ir8Al21.22 binary intermetallic compound was synthesized using arc melting technique. Its crystal structure probed by single-crystal X-ray diffraction is a superstructure variant of the previously reported cubic IrAl2.75 compound. Ir8Al21.22 crystallizes in the Fmm2 space group with the unit cell parameters of a = 15.3307(9) Å, b = 15.3226(10) Å, c = 15.3129(9) Å, and V = 3597.1(4) Å3. The crystal structure contains columns of interpenetrating distorted icosahedral clusters – a characteristic feature of the approximant phases and quasicrystals. Electronic structure calculations indicate strong hybridization between valence orbitals of iridium and aluminum atoms accompanied by the formation of pseudogap, which separates the valence and conduction bands.

Microstructure and mechanical properties of Mg/Al laminated composite: The effect of transition layer thickness

This study successfully prepared Mg/Al laminated composites with various thicknesses of pure Cu transition layer via extrusion, overcoming the challenge of forming of Mg/Al composite plates through stacked extrusion technology. The effects of varying Cu layer thicknesses on the microstructure, mechanical properties, and fracture behaviors were systematically investigated. Microstructure analysis showed an uneven Cu layer distribution at the interface of the composite plate, characterized by alternating thicker and thinner layers, which stemmed from the low fluidity of pure Cu during extrusion. Although the thicker Cu layer significantly inhibited the diffusion of Mg and Al elements, there was still a significant enrichment of Mg-Al intermetallic compounds (IMCs) in the thinner Cu layer. There hard and brittle IMCs caused cracking during the deformation process. Increasing Cu layer thickness did not significantly affect the microstructure but contributed to the decrease of strength owing to increased stress concentration. Moreover, the thicker Cu layer exacerbated its uneven distribution and Mg-Al IMCs enrichment at the interface, resulting in a pattern of first decreasing and then increasing elongation and shear strength of the laminated composite.

Investigating laser and ultrasonic welding of pouch cell multi-foil current collectors for electric vehicle battery fabrication

The escalating necessity for more efficient and defect-free joining of ‘ultra-thin foil collectors-to-tabs’ in electric vehicle (EV) Li-ion pouch cells motivates this study. The prevalent ultrasonic welding (USW) method for these joint types, faces limitations such as design constraints and access requirements, laser welding (LW) emerges as a promising alternative offering flexibility, one-side access and faster speeds with efficient heat input. This study aims to investigate the feasibility of LW as a viable alternative to USW for joining current collectors-to-tab joints. It compares the mechanical, metallurgical, electrical and thermal analysis of the joints to evaluate both welding techniques for joint defects. The comparison of solid-state material mixing during USW and the intermixing of aluminium (Al) and copper (Cu) during fusion LW using EDX analysis presents interesting observations in the study. The USW generates a thin transition layer with intermetallic compounds (IMCs) attributed to the diffusion of Cu into the Al matrix during joining, which is comparatively lower as in the case of LW with higher material mixing with brittle IMCs like Al2Cu and Al4Cu9. However, the joint strength of LW is comparatively lower than the USW joint attributed to the reduced fusion zone area. Furthermore, from the electrical contact resistance and the joint temperature analysis, it was found that the resistance and temperature vary by as much as 13% and 6%, respectively, for the 50 A and 75 A passing currents when the USW is replaced with the LW process.

Enabling Invar to Ti6Al4V transitions through copper in functionally graded laser powder bed fused components

This study examines the microstructural evolution, elemental distribution, phase composition, and hardness variations in multi-material samples fabricated using Laser Powder Bed Fusion (LPBF) with Invar and Ti6Al4V with compositional gradients mediated by copper. A range of compositional transitions from Invar to Ti6Al4V with different copper fractions are reported. Defects such as gas and keyhole pores were detected in well-deep keyhole mode areas, while lack of fusion defects were observed in samples with pure Cu interlayers due to poor wettability and processing parameter variations. Crack formation between interlayer gradient zones and Invar regions was linked to FeNi and CuNi intermetallic phases. Intermetallic compounds (e.g., FeNi, CuNi, TiFe, TiNi) significantly influenced the microstructure and mechanical performance. Vickers hardness testing shows varying hardness across different builds, with the highest hardness being observed in the gradient zone enabled by pure copper (approximately 620 HV). This study also underscores the need for tailored component design linking build processing parameters and compositional transitions in multi-material LPBF to achieve desired properties and component structural behaviour.

Physico-Chemical and Microstructural Analysis of Al-Mg-Si Alloy Matrix Composites Reinforced Groundnut Shell ash Particulates

Metal matrix composites are an appealing alternative to monolithic metals for a variety of technical applications due to their superior mechanical and physical properties throughout a broad range of operating conditions. In the current study, different weight percentages of 150 µm groundnut shell ash (GNSA) particles (2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 25% and 30%) were used to reinforce Al-Mg-Si alloy. Stir-casting was used to prepare the composite in a permanent mild steel mould. A number of the composites' physical, chemical, and microstructural characteristics (density, percentage porosity, XRF and SEM-EDS) were assessed, compared, and analysed with those of the matrix alloy. Oxides that could enhance the composites' mechanical, physical, and structural qualities were found during the structural assessment evaluation of the reinforcement. The microstructural analysis demonstrated that the GNSA reinforcements' secondary phase was uniformly distributed throughout the primary phase of the Al-Mg-Si alloy matrix. The added GNSA particles decreased the produced composite's density below that of the base alloy, and the percentage porosity of the composites rose as the groundnut shell ash content increased and remained within the upper limit allowed for cast aluminium metal matrix composites. The composites that were created showed evidence of intermetallic compound formation.

Hydrogen, Oxygen, and Lead Adsorbates on Al13Co4(100): Accurate Potential Energy Surfaces at Low Computational Cost by Machine Learning and DFT-Based Data.

Intermetallic compounds are promising materials in numerous fields, especially those involving surface interactions, such as catalysis. A key factor to investigate their surface properties lies in adsorption energy maps, typically built using first-principles approaches. However, exploring the adsorption energy landscapes of intermetallic compounds can be cumbersome, usually requiring huge computational resources. In this work, we propose an efficient method to predict adsorption energies, based on a Machine Learning (ML) scheme fed by a few Density Functional Theory (DFT) estimates performed on n sites selected through the Farthest Point Sampling (FPS) process. We detail its application on the Al13Co4(100) quasicrystalline approximant surface for several atomic adsorbates (H, O, and Pb). On this specific example, our approach is shown to outperform both simple interpolation strategies and the recent ML force field MACE [arXiv.2206.07697], especially when the number n is small, i.e., below 36 sites. The ground-truth DFT adsorption energies are much more correlated with the predicted FPS-ML estimates (Pearson R-factor of 0.71, 0.73, and 0.90 for H, O and Pb, respectively, when n = 36) than with interpolation-based or MACE-ML ones (Pearson R-factors of 0.43, 0.39, and 0.56 for H, O, and Pb, in the former case and 0.22, 0.35, and 0.63 in the latter case). The unbiased root-mean-square error (ubRMSE) is lower for FPS-ML than for interpolation-based and MACE-ML predictions (0.15, 0.17, and 0.17 eV, respectively, for hydrogen and 0.17, 0.25, and 0.22 eV for lead), except for oxygen (0.55, 0.47, and 0.46 eV) due to large surface relaxations in this case. We believe that these findings and the corresponding methodology can be extended to a wide range of systems, which will motivate the discovery of novel functional materials.

Microstructural evolution of Fe-25 W powder beds during CO2-H2 redox cycling at 800 °C

Fixed powder beds of Fe-25 W at% powders show excellent resistance to degradation during CO2-H2 redox cycling at 800 °C, releasing CO and H2O, respectively, with 100 % metal utilization. During cycling up to 165 full redox cycles (∼500 h), the reaction kinetics improve with cycle number and a stable, hierarchically-porous microstructure forms that shows neither sintering nor densification. The sintering inhibition provided by W addition to Fe stems from the formation of Fe-W mixed phases: as an intermetallic compound (Fe2W) in the reduced state and as a ternary oxide (FeWO4) in the oxidized state. In addition to the large channels running between coarse (100 µm) powder agglomerates, each agglomerate in the powder bed shows both microporosity due to sintering inhibition, and submicron porosity due to a chemical vapor transport reduction mechanism that is active when FeWO4 is reduced by H2 at high temperature. This hierarchical porosity enables fast reactions due to the short diffusion distance to free surfaces, and non-tortuous gas flow through the powder bed. As a result, under high CO2 flow, the CO2:CO ratio is sufficiently high to oxidize Fe3O4 to Fe2O3, improving the CO conversion capability on a per-mole basis.