Alloy Foams Research Articles

Influence of Gas Pressure and Blowing Agent Content on the Formation of Aluminum Alloy Foam

Apart from density and alloy composition, the structure of solid metallic foams determines their mechanical performance. Herein, the effect of ambient pressure on the foaming behavior of AlSi6Cu4 precursors is studied. In situ X‐ray radioscopy is applied while foaming in a furnace chamber pressurized up to 40 bar. The content of the blowing agent (TiH2) is varied for each of the pressures chosen. The foam density and morphology are analyzed quantitatively using time‐resolved X‐ray radioscopy sequences and postsolidification X‐ray tomography data. The optimal content of blowing agent as well as the pore sizes and distributions is found to depend strongly on the ambient pressure. At high pressures very small, round, and uniformly distributed pores are formed and crack formation is avoided during the gas nucleation stage, which helps to prevent structural defects. Adjusting the ambient pressure allows for better control of the foam structure and density, which is relevant for commercial production and application.

Effect of cell structure on mechanical and bio-corrosion behavior of biodegradable Mg-Zn-Ca foam

This study investigates the fabrication, mechanical properties, and corrosion behavior of biodegradable Mg-1.5Zn-1Ca alloy foams. A series of the alloy foams produced with spherical cells in five different cell sizes between 600 and 2800 µm using the infiltration process. The compressive mechanical properties and corrosion behavior of the foams were evaluated. It was found that increasing the porosity content of the foams led to decreasing the mechanical properties, while the pore size had no significant effect on the mechanical properties. Compared to a pure Mg foam, the precipitation of eutectic phases (α-Mg + Mg6Zn3Ca2 + Mg2Ca) at the grain boundaries of the alloy foams caused a higher compressive strength. Additionally, the Mg-Zn-Ca alloy foams significantly showed a higher corrosion resistance than the pure foam due to the beneficial effects of zinc and calcium. It was also found that an increase in the pore size of the alloy foam increased the corrosion resistance. Accordingly, the highly porous foam with a pore size of ~ 2800 µm and porosity content of ~ 64% exhibited a corrosion rate near the dense Mg-Zn-Ca specimen.

Simulation and modeling of different cell shapes for closed-cell LM-13 alloy foam for compressive behavior

Abstract In the present investigation, a two-dimensional (2D) finite element (FE) model of closed-cell AlSi12Mg1Cu1 alloy foam (AAFs) of 0.35 relative density of different cell shapes, i.e., square, hexagonal, octagonal, and circular shaped cell established with the help of ABAQUS simulation software. Experimentation is also done for 0.35 relative density metal foam to report its compressive behavior. The plateau stress σ p l $\left(\right.{\sigma }_{pl}$ ) and energy absorption capacity (E ab) of AAFs (ρ rd = 0.35) properties are calculated from the plotted stress–strain graph and a significant effect of cell shape on compressive performance observed. By SEM characterization, it was noted that the experimental specimen also had near circular cells. The strength and energy absorption values are calculated for square-shape, circular-shaped, octagonal-shaped, and hexagonal-shaped cells in descending order from maximum to minimum. A convergence study is also carried out concerning the number of elements to obtain the most accurate FE results.

Non-Lubricated Sliding Wear Performance of LM13 Alloy Foam and its Composite Foams Reinforced with ZrSiO4

Non-Lubricated Sliding Wear Performance of LM13 Alloy Foam and its Composite Foams Reinforced with ZrSiO4

LixCu alloy nanowires nested in Ni foam for highly stable Li metal composite anode

Porous metal architectures are widely adopted as three-dimensional conducting scaffolds for constructing Li metal composite anodes, whereas their macropores hinder their practical application due to limited surface area and large pore size of few hundred micrometers. In this work, a network of LixCu solid solution alloy nanowires is in situ formed via infiltrating molten Li-Cu alloy into Ni foam and subsequent cooling treatment, whereby a three-component composite anode consisting of Li metal, LixCu alloy, and Ni foam is fabricated. The LixCu nanowires nested as secondary frame split the macropores into micropores, enlarging the active surface area and inducing uniform Li deposition significantly. The lithiophilicity of the alloy wires and the shrunken void size built by the hierarchical architecture can further tune the nucleation and growth behavior of Li. The multiscale synergetic effect between the primary and secondary scaffold guarantees the composite anode sheet with extraordinarily long-term cycling stability even under high current rates.

Suppression of the Hydrogen Evolution Reaction Is the Key: Selective Electrosynthesis of Formate from CO2 over Porous In55Cu45 Catalysts.

Direct electrosynthesis of formate through CO2 electroreduction (denoted CO2RR) is currently attracting great attention because formate is a highly valuable commodity chemical that is already used in a wide range of applications (e.g., formic acid fuel cells, tanning, rubber production, preservatives, and antibacterial agents). Herein, we demonstrate highly selective production of formate through CO2RR from a CO2-saturated aqueous bicarbonate solution using a porous In55Cu45 alloy as the electrocatalyst. This novel high-surface-area material was produced by means of an electrodeposition process utilizing the dynamic hydrogen bubble template approach. Faradaic efficiencies (FEs) of formate production (FEformate) never fell below 90% within a relatively broad potential window of approximately 400 mV, ranging from -0.8 to -1.2 V vs the reversible hydrogen electrode (RHE). A maximum FEformate of 96.8%, corresponding to a partial current density of jformate = -8.9 mA cm-2, was yielded at -1.0 V vs RHE. The experimental findings suggested a CO2RR mechanism involving stabilization of the HCOO* intermediate on the In55Cu45 alloy surface in combination with effective suppression of the parasitic hydrogen evolution reaction. What makes this CO2RR alloy catalyst particularly valuable is its stability against degradation and chemical poisoning. An almost constant formate efficiency of ∼94% was maintained in an extended 30 h electrolysis experiment, whereas pure In film catalysts (the reference benchmark system) showed a pronounced decrease in formate efficiency from 82% to 50% under similar experimental conditions. The identical location scanning electron microscopy approach was applied to demonstrate the structural stability of the applied In55Cu45 alloy foam catalysts at various length scales. We demonstrate that the proposed catalyst concept could be transferred to technically relevant support materials (e.g., carbon cloth gas diffusion electrode) without altering its excellent figures of merit.

Compressive Properties of Electroless Ni-P Coating Reinforced Magnesium Alloy Foams

In this study, the open-cell Mg-2Zn-0.4Y foams were prepared by infiltration casting method. The Ni/Mg hybrid foams were prepared by electroless Ni-P coating on the foam struts to improve the compressive strength and energy absorption capacity. The compressive properties of the Mg alloy foams and Ni/Mg hybrid foams were studied by quasi-static compressive test. The experimental results show that the Ni-P coating is composed of crystallites. The Ni-P coating can significantly enhance the compressive strength, energy absorption capacity and energy absorption efficiency of the foams.

Aluminium Alloy Foam Modelling and Prediction of Elastic Properties Using X-ray Microcomputed Tomography

X-ray microcomputed tomography has been gaining relevance in the field of cellular materials to characterize materials and analyse their microstructure. So, here, it was used together with finite element modelling to develop numerical models to estimate the effective properties (Young’s modulus) of aluminium alloy foams and evaluate the effects of processing on the results. A manual global thresholding technique using the mass as a quality indicator was used. The models were reconstructed (Marching Cubes 33), then simplified and analysed in terms of mass and shape maintenance (Hausdorff distance algorithm) and face quality. Two simplification procedures were evaluated, with and without small structural imperfections, to evaluate the impact of the procedures on the results. Results demonstrate that the developed procedures are good at minimizing changes in mass and shape of the geometries while providing good face quality, i.e., face aspect ratio. The models are also shown to be able to predict the effective properties of metallic foams in accordance with the findings of other researchers. In addition, the process of obtaining the models and the presence of small structural imperfections were shown to have a great impact on the results.

Preparation of Ni-Fe alloy foam for oxygen evolution reaction

NiFe oxyhydroxide and hydroxide have been proven to be efficient and earth-abundant non-noble metal catalysts for the oxygen evolution reaction (OER). However, the fragile nature of these oxyhydroxides or hydroxides severely reduces the long-term stability and hinders the industrial applications. Meanwhile, the poor electrical conductivity of these materials also has seriously led to the higher overpotential when applying to the OER. Herein, a novel method using polyurethane (PU) sponge as electroplating was carried out to design NiFe alloy foam with different Fe content for OER. The physical properties of NiFe alloy foams were characterized by Scanning Electronic Microscopy (SEM), Energy Dispersive System (EDS) and X-Ray Diffraction (XRD), respectively, suggesting that the porous NiFe alloy is formed with uniform distribution of Ni and Fe. The OER performance was tested by Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS), I-t, etc. The results showed that the doped Fe could significantly improve the conductivity and OER performance of Ni foam. The NiFe alloy foam with 30% Fe exhibited 292 mV overpotential at 10 mA/cm2 and the Tafel slope 126.12 mV/decade in alkaline solution with excellent long-term stability. Without any complex electrode preparation processes and binders, NiFe alloy foam is much convenient to use as anode of water splitting in alkaline media for industrial applications.

Effect of Laser Forming on the Energy Absorbing Behavior of Metal Foams

Abstract Metal foam is light in weight and exhibits an excellent impact absorbing capability. Laser forming has emerged as a promising process in shaping metal foam plates into desired geometry. While the feasibility and shaping mechanism has been studied, the effect of the laser forming process on the mechanical properties and the energy absorbing behavior in particular of the formed foam parts has not been well understood. This study comparatively investigated such effect on as-received and laser formed closed-cell aluminum alloy foam. In quasi-static compression tests, attention paid to the changes in the elastic region. Imperfections near the laser irradiated surface were closely examined and used to help elucidate the similarities and differences in as-received and laser formed specimens. Similarly, from the impact tests, differences in deformation and specific energy absorption were focused on, while relative density distribution and evolution of foam specimens were numerically investigated.

Axial crashworthiness performance of foam-based composite structures under extreme temperature conditions

Due to their unique properties, metal foams can be used under extreme temperature conditions. To this end, this paper investigates the influence of temperature (−196, −25, 25 and 250 °C) on the axial crashworthiness performance of foam-based composites. The composite structures are made of aluminum thin-walled circular tubes, filled with aluminum alloy (A356) foam. It is found that the highest mechanical characteristics are obtained at the cryogenic temperature (−196 °C) due to the hardening behaviour of the matrix material in both foam and tube. Contrary, the softening behaviour of the matrix material at high temperature (250 °C) decreases the mechanical properties of the composite material. Between two extreme temperatures, a transition from brittle-to-ductile deformation occurs. The deformation transition is observed both on the stress–strain curves (gradual reduction of oscillations of the plateau region) and the macroscopic images of the compressed samples (changing the crushing mode from non-axisymmetric < Diamond > to axisymmetric < Concertina >). Moreover, due to the foam-tube interaction effect, the experimental results show that the quasi-static compressive behavior and collapse mechanisms of the composite structures has considerably improved (over 50% in some cases). Furthermore, the strength properties and energy absorption performances of the foam filled tube shows significantly higher values (almost double) compare to empty one.

Compressive behavior of a Zn-22wt%Al-2wt%Cu cellular alloy with different densities, microstructures and cell shapes

Zn22Al2Cu cellular alloy was prepared with six different densities, two microstructures and two cell shapes to determine the effect of these factors on its compressive behavior. NaCl granules with sharp edges, as purchased and with smooth edges obtained by roughly polishing the purchased granules were used as spacers. The elaboration process of the alloy foam consisted of melting the alloy, immersing the granules in the liquid alloy, air-cooling and then dissolving the salt in boiling water. The matrix obtained with the materials had an as-cast microstructure, and a fine microstructure, which was achieved with a heat treatment applied prior to dissolving the NaCl granules. Samples were tested in compression at a 10-3 s-1 strain rate. The smooth shape of the cells caused that the as-cast microstructure in the matrix produces an elastic behavior, which is described by the equation derived by Ashby for the relative elastic modulus and the relative density of sponges. The same type of cell shape embedded in the fine microstructure produces an elastic behavior in compression that depends on the density, which is typical of very low-density foams, although much lower than those achieved in this study. Compressive behavior is chaotic when cells have sharp shape, regardless microstructure type. The alloy studied with 4 mm mean size cells has a compression behavior like a sponge or low-density foam, when its cell walls have smooth contours, and as-cast or fine microstructure, respectively.

Failure Mechanisms of an Al 6061 Alloy Foam under Dynamic Conditions.

The interesting properties of Al 6061 aluminum foams have boosted the research on the correlation between foam composition and morphology and its mechanical response under dynamic conditions. In this study, ingots of an Al 6061-T4 foam were sectioned and analyzed in order to determine their microstructural and morphological characteristics, and then quasi-static and dynamic tests (10−3 to 3 × 102 s−1) were carried out to determine the material mechanical behavior. Dynamic tests, carried out by using the split Hopkinson bar, highlighted that the studied foam is characterized by a very good energy absorption capability, due to its ductile behavior. Nevertheless, the conducted research showed that cell morphology and distribution affect its mechanical behavior in dynamic conditions in which localized cell collapse may result in a decreased energy absorption and efficiency of the foam.

Microstructure and mechanical behaviour of Ti-Cu foams synthesized via powder metallurgy technique

In the present study titanium based copper alloy foams were synthesized using acrawax as a space holder through powder metallurgy route. The effects of distinct pore size range and Cu content on the microstructural features, density, compressive and flexural behaviour was investigated. Results show that the amount of microporosity generated was more in case of foams with coarser pores than finer ones and also it increased with increase in Cu content. The presence of fine pores and lower amount of Cu led to generation of minimal amount of microporosity; resulting into greater relative density of Ti-Cu foams. The plastic collapse stress, plateau stress and bending strength of Ti-Cu foams decreased while densification strain increased with increase in Cu content. The maximum value of plastic collapse stress is reported for Ti-3Cu foam with fine pores. The plateau strength and bending strength of Ti-3Cu foam with fine pores was found to be higher than that of Pure Ti foams and was found to be the most optimized in terms of the characteristic features. The higher values of relative density, plateau and bending strength of Ti-3Cu foams makes them more preferable over pure Ti foams for implants applications.

Enabling Stable Zn Anode via a Facile Alloying Strategy and 3D Foam Structure

AbstractAqueous zinc‐ion battery (AZIB) has become a promising candidate in grid energy storage due to its low cost, environmental friendliness, and high safety. However, AZIB usually suffers from uncontrollable zinc deposition and dendrite growth as well as hydrogen evolution and passivation on the surface of zinc anode. To address the above issues, a unique 3D Zn alloy foam anode built from Zn–Sn–Pb alloy in 3D Cu foam is constructed by a facile hot dipping method. The proposed 3D Zn alloy anode, through introducing elements Sn and Pb, enhances the hydrogen evolution overpotential, reduces the corrosion current, greatly mitigates the self‐corrosion in the electrolyte, and efficiently inhibits the growth of Zn dendrite during cycling. Importantly, such Zn alloy engineering together with a 3D Cu foam current collector enables highly stable Zn storage properties. The full cell assembled using the proposed 3D Zn alloy anode and MnO2 nanosheet cathode exhibits superior reversible capacity (103.4 mAh g−1) and excellent cycling stability (capacity retention of 87% over 4000 cycles) at 1.8 A g−1.

Partially open cell Ti-6Al-2Co ternary alloy foams with a range of size and volume fraction of spacer particle

Partially open cell Ti-6Al-2Co alloys foams of varying cell (pore) size (0 to 500 µm) and volume fraction (40 to 70%) are made by varying the space-holder size (SHS) and volume fraction. The increase of space-holder (spacer) size increased the cell size and cell-wall thicknesses, which led to increased plateau stress, energy absorbed (Toughness), hardness and Young’s modulus. Further, increased spacer content and decrease of strain rate; reduced the strength, toughness, and modulus of Ti6Al2Co ternary alloy foams. The corrosion rate was found to be decreasing with increase of particle size of space-holder Also, the corrosion rate and weight loss percent increases with increase in cell volume fraction. Further, the Ti6Al2Co alloy foam’s mechanical properties were found to have a trend of power-law relations with relative densities.

New insight into fabrication of shaped Mg–X alloy foams with cellular structure via a gas release reaction powder metallurgy route

Shaped Mg alloy foams with closed-cell structure are highly interested for a great potential to be utilized in the fields where weight reduction is urgently required. A powder metallurgical method, namely gas release reaction powder metallurgy route to fabricate Mg–X (X=Al, Zn or Cu) alloy foams, was summarized. The principles on shaped Mg–X foams fabrication via the route were proposed. In addition, the effects of alloying elements, sintering treatment and foaming temperatures on fabrication of shaped Mg–X alloy foams were investigated experimentally. The results show that the key to ensure a successful foaming of Mg–X alloy foams is to add alloying metals alloyed with Mg to form lower melting (< 600 °C) intermetallic compounds by the initial sintering treatment. The foaming mechanism of Mg–X alloy foams also has been clarified, that is, the low-melting-point Mg-based intermetallic compounds melt first, and then reactions between the melt and CaCO3, a foaming agent, release CO gas to make the precursor foamed and finally shaped Mg–X alloy foam with a promising cellular structure is prepared. This route has been verified by successful fabrication on shaped Mg–Al, Mg–Zn and Mg–Cu foams with cellular structure.

Efficient energy absorption of functionally-graded metallic foam-filled tubes under impact loading

Abstract The deformation behavior and crashworthiness of functionally-graded foam-filled tubes (FGFTs) under drop-weight impact loading were investigated. Closed cell aluminum, A356 alloy and zinc foams fabricated by the liquid state processing were used as axial grading fillers for the manufacture of single-layer and multilayer structures with different configurations. The results indicate that the deformation of multilayer foam filled tubes initiates from the low-strength components, and then propagates in the high-strength components through the gradual increment of stress. The use of more A356 alloy and aluminum foam layers provides greater specific energy absorption (SEA) for the graded structures, whereas the high-strength zinc foam has no positive effect on the crash performance. The progressive collapse of graded structures consisting of the aluminum and A356 alloy foams occurs in a symmetric mode under quasi-static and drop-weight impact conditions. However, the zinc foam causes a combination of symmetric and extension modes as well as greater localized deformation under dynamic loading and greater local rupture in quasi-static loading condition. The Al−A356 foam-filled tubes with a combination of the highest SEA (10 J/g) and the lowest initial peak stress (σmax of 10.2 MPa) are considered as the best lightweight crashworthy structures.

Fabrication and evaluation of percent porosity and density reduction of aluminium alloy foam

Aluminium alloy foams are manufactured by various methods, which include foaming of molten aluminum alloy by gas injection and powder metallurgical processing. Non-conventional methods such as direct energy deposition, syntactic method of metal foam fabrication have also been developed for the manufacturing of aluminium alloy foams. Aluminium alloy foams are cellular structure which consists of solid metal such as aluminium, steels and iron with micro pores filled with gases such as hydrogen, carbon di oxide, nitrogen, argon etc. In this research work in order to fabricate aluminum alloy 6063 foam, first aluminium alloy 6063 was melted by using stir casting method as it is economical and simple, 2 wt% titanium hydride was added and mixed into the molten aluminium alloy 6063 at temperature 800 ˚C and then the melt was allowed to cool down to room temperature in order to obtain aluminium alloy 6063 foam. The percent porosity and density of the fabricated aluminium alloy foam is determined with the help of Archimedes principle.

Microstructural Characteristics and Mechanical Properties of 7075 Aluminum Alloy Foam Sandwich Panels Fabricated via Integrated Forming and Foaming

Microstructural Characteristics and Mechanical Properties of 7075 Aluminum Alloy Foam Sandwich Panels Fabricated via Integrated Forming and Foaming