Alloy Foams Research Articles

MICROSTRUCTURE AND WEAR BEHAVIOR CHARACTERIZATION OF STIR-CAST ALUMINUM 6063 ALLOY AND ITS FOAM: A COMPARATIVE STUDY

In this research work, aluminum 6063 alloy foam was synthesized through stir casting using varying amounts of titanium hydride as a foaming agent. A comparative microstructural and wear behavior analysis of stir-cast aluminum 6063 alloy and its foam is presented. The oxide and aluminide phases present as intermetallic compounds in the stir-cast aluminum 6063 alloy foam ensure the stability of the synthesized foam. In order to optimize the effect of wear parameters on the tribological properties of stir-cast aluminum 6063 alloy foam, the L933 orthogonal array (OA) was designed and modeled statistically. The tribological properties of stir-cast aluminum 6063 alloy and its foam were evaluated by pin-on-disc tests. The optimal tribological properties of the synthesized foam are 0.29 coefficient of friction, 8.6 N frictional force, and 0.00025 mm3/N-m specific wear rate. The tribological properties of stir-cast aluminum 6063 alloy foam are superior to those of aluminum 6063 alloy and comparable to other aluminum foams described in the literature.

Performance Assessment on the Manufacturing of Zn-22Al-2Cu Alloy Foams Using Barite by Melt Route

A barium-rich Celestine (Sr,Ba)SO4 concentrate from the primary Mexican ore production was used as a thickening agent to produce closed-cell Zn-22Al-2Cu alloy foams, while calcium carbonate was used as a foaming agent. The microstructure and mechanical properties of the foams were analyzed by optical microscopy, scanning electron microscopy, and compression tests, respectively. The Zn-22Al-2Cu alloy foams showed a typical lamellar eutectic microstructure, constituted by a zinc-rich phase (η) and a (α) solid solution that was richer in aluminum, while a copper-rich (ε) phase was formed in the interdendritic regions. The SEM micrographs show the presence of small particles and aggregates that are randomly scattered in the cell walls and correspond to unreacted calcite and Celestine–Barian particles, especially for the higher barite addition. The compressive curves showed smooth behavior, wherein the particles at the cell walls did not affect the foam’s compressive behavior. The trial containing 1.5 wt. % of BaSO4 and 1.0 wt. % of CaCO3 showed a higher energy absorption capacity of 5.64 MJ m−3 because of its highest relative density and lowest porosity values. The Celestine–Barian concentrate could be used as a foaming agent for high melt-point metals or alloys based on the TGA results.

Comparison of Energy Absorptive Capacities of Different Aluminum Alloy Foams Placed Inside the Crash Box

Increasing population worldwide and the resulting increasing number of automobiles increase the risk of traffic accidents. Due to this increasing risk, automobile manufacturers take various safety measures to protect drivers and passengers in case of possible accidents. Crash boxes are one of the passive safety system elements that are the first to absorb the impact in the event of a front or rear impact accident, absorbing the resulting deformation energy and ensuring that it is transmitted into the car at the least possible level. Therefore, increasing the energy absorption ability of crash boxes is an extremely important issue. In this study, it was aimed to increase the energy absorption capabilities by placing aluminum foam based materials produced by using the powder metallurgy method using three different aluminum alloys (Al2024, Al5083, and Al6061) inside the crash boxes, which are normally manufactured as hollow. In addition, the produced aluminum foams were compared in terms of pore sizes with SEM images. It can be said that Al6061 is the most ideal material among the alloys used in terms of pore structure and homogeneity. On the other hand, Al6061 alloys produced the greatest damped energy value within the parameters of the investigation, 221.711 J. This value was 169.556 J for Al2024 alloy and 214.101 J for Al5083 alloy. As a result, it was concluded that the amount of energy absorption can be increased by about 4-5 times by using metallic foams produced using aluminum materials compared to the empty crash box.

Al and A356 Alloy Foam Castings Modified with Low Concentrations of Nano-Sized Particles: Structural Study and Compressive Strength Tests

Aluminum and A356 alloy foam castings are produced using a melt-foaming method. Prior to foaming, the melt is modified with nano-sized particles (SiC, TiN, or Al2O3). The nano-sized particles are mixed with micro-sized Al particles, which are ultrasonically treated and hot-extruded. Thus, the so-called “modifying nano-composition” is obtained. The resulting compositions are introduced into the melt of the Al foam at the following mass concentrations of nanoparticles: SiC: 0.038 wt. %; TiN: 0.045 wt. %; and Al2O3: 0.046 wt. %. For the A356 foam, we use the following concentrations: SiC: 0.039 wt. %; TiN: 0.052 wt. %; and Al2O3: 0.086 wt. %. The macrostructure of the foam castings is investigated by CT scanning and 3D analysis. The pore size distributions and accumulative fraction dependencies are determined for all samples. The microstructure of the foam castings is investigated by SEM-EDS analysis. The results confirmed the presence of individual nano-sized particles, as well as clusters of particles in foam walls. The conducted compression tests show a significant increase in the plateau stress (up to 237%) of the modified aluminum foam castings compared to non-modified castings. However, a similar effect of the nano-compositions on A356 alloy foam castings is not observed. The obtained results show that the above-indicated concentrations of nanoparticles can positively influence the mechanical properties of aluminum foam castings. The novelty of the current study is two-fold: (1) such low concentrations of added nanoparticles have never been used before to alter Al foam’s properties, and (2) an original method of introducing the nanoparticles into the melt is applied in the form of nano-compositions.

Constructing dual-scale high-entropy alloy/polymer interpenetrating networks to develop a lightweight composite with high strength and excellent damping capacity

Lightweight materials with high strength and excellent damping capacity are of great significance for reducing weight and vibration and maintaining stability in industrial applications. However, these characteristics are usually difficult to achieve simultaneously in traditional damping materials. Here, we provide a design strategy for dual-scale interpenetrating networks. By infiltrating the viscoelastic polymer containing CrMnFeCoNi nanoalloy/carbon nanotube networks into CrMnFeCoNi high-entropy shape memory alloy foam with a three-dimensional network structure, the dual-scale CrMnFeCoNi/polymer interpenetrating phase composite was developed. When the carbon nanotube loading is 2 wt%, the composite exhibits a compressive strength of 37.2 MPa and an energy absorption capacity of 22.5 MJ·m−3 (ε = 65 %), with a mere density of 2.528 g·cm−3. In the temperature range of 20 ∼ 150℃, its loss factor exceeds 0.132 with a peak value of 0.206. Compared with CrMnFeCoNi foam, its compressive strength, energy absorption capacity and peak internal friction are increased by 85 %, 65 % and 156 %, respectively. The construction of dual-scale interpenetrating networks introduces high-density interfaces, and the coupling of multi-scale intrinsic damping and interface damping endows the composite with high ground-state damping. The superposition of the phase transformation peak of CrMnFeCoNi foam and the glass transition peak of polymer composite matrix enables a wide damping temperature window. This study offers a new perspective for developing high-performance damping materials.

Effect of Calcium Addition on the Aluminum Alloy A201 Foam

To study the effect of calcium on the porosity, sphericity, and microstructure of Al–Cu foams, a gradient calcium content (0.5, 1.0, 1.5, and 2.0 wt%) is added into aluminum A201 alloy (Al–Cu alloy) for the cellular aluminum foam preparation via the melt foaming method (TiH2 is used as a bubbling agent). Thereafter, the porosity of the prepared Al foams and their pore size are found to increase, and the sphericity of pores tends to approach to unit with calcium addition. This phenomenon is then explained through the modified thermophysical properties (i.e., surface tension and viscosity) of A201 alloy melts caused by the calcium addition. After the microstructure analysis, a bunch of secondary phases in the A201 + Ca alloy foams, e.g., CalAl2Si2, Al2Cu, and Al20CaTi2 as well as an eutectic phase with a great copper content Al8CaCu4 are detected by means of scanning electron microscopy/energy‐dispersive X‐Ray spectroscopy and X‐Ray diffraction analysis.

Damage kinetics and compression behavior of Al alloy foam using in situ SRμCT

Damage kinetics and compression behavior of Al alloy foam using in situ SRμCT

Controllable La Deficiency Engineering within Perovskite Oxides for Enhanced Overall Water Splitting.

Recently, perovskite (ABO3) nanomaterials have been widely explored as a class of versatile electrocatalysts for oxygen evolution reactions (OER) due to their remarkable compositional flexibility and structural tunability, but their poor electrical conductivity hinders hydrogen evolution reaction (HER) activity and further limits the large-scale application of perovskite oxide in overall water splitting (OWS). In this study, hollow-nanotube-structure LaxCo0.4Fe0.6O3-δ (x = 1.0, 0.9, and 0.8) perovskites with superior HER/OER activity were synthesized on nickel-iron alloy foam (denoted LaxCoFe/NFF) using hydrothermal with a subsequent calcination strategy. Among them, La0.9CoFe/NFF not only exhibited extraordinary HER electrocatalytic performance (160.5 mV@10 mA cm-2 and 241.0 mV@100 mA cm-2) and stability (20 h@10 mA cm-2), but also displayed significant OER electrocatalytic activity (234.7 mV@10 mA cm-2 and 296.1 mV@100 mA cm-2) and durability (20 h@10 mA cm-2), outperforming many recently reported HER/OER perovskite catalysts. The increase in oxygen vacancies caused by the introduction of La deficiency leads to the expansion of the lattice, which greatly accelerates the HER/OER process of La0.9CoFe/NFF. Additionally, the naturally porous skeleton can prevent catalysts from aggregating as well as delay the corrosion and dissolution of catalysts in the electrolyte under high applied potentials. Furthermore, the assembled two-electrode configuration, utilizing La0.9CoFe/NFF (cathode and anode) electrodes, only requires a low cell voltage of 1.573 V at 10 mA cm-2 for robust alkaline OWS, accompanied by remarkable durability over 20 h. This work provides inspiration for the design and preparation of high-performance and stable bifunctional perovskite electrocatalysts for OWS.

Nonlinear low-velocity impact analysis of sandwich plates with titanium face sheets and porous aluminum core reinforced by GPLs

This study examines the nonlinear dynamic response of sandwich plates under low-velocity impacts (LVIs), which consist of a porous aluminum foam core with functionally graded (FG) graphene platelets (GPLs) reinforcement and two titanium alloy face sheets. The finite element method is employed to perform the numerical simulations and the Hertz contact theory is used to model the impact behavior. The generic Halpin-Tsai model, which incorporates the porosity effect, is adopted to estimate the mechanical properties of core made of the FG-GPLRC, based on the experimental data of the closed-cell aluminum alloy foam. The simulation results reveal that the FG-X configuration has the highest impact resistance, and that the addition of GPLs improves the impact performance. Moreover, a thicker core can reduce both the first contact time and the vibration period of plates, while a looser boundary condition can prolong the vibration time after the first impact. Additionally, a higher impactor velocity, mass and radius lead to a higher deflection and contact force. The oblique impact decreases the impact energy. This work provides a lighter and stiffer design for structure engineers when components suffer low-velocity impact.

Numerical Simulation of Aluminum Foams by Space Holder Infiltration

AbstractThis study explores the simulation and analysis of the infiltration process for manufacturing A356 aluminum alloy foams using vacuum pressure. The infiltration technique, known for its versatility in liquid-state metal processing, is widely employed for metal foam production due to its ease of application. The study investigates the relationship between the geometric parameters of the preform, system pressure, and filling times, revealing a correlation. The simulation using the Flow 3D software determines the pressure and vacuum time required to achieve successful aluminum foam without filling failures. Experimental validation through infiltration casting using NaCl as a removable preform aligns with the simulated results, yielding high-quality aluminum foam samples with diverse pore sizes (0.5 mm, 1.0 mm, and 2.0 mm), uniform and interconnected pore distribution, average porosity percentages of 65%, and a relative density of 0.35. The research contributes insights into optimizing the infiltration process for aluminum foam fabrication, bridging the gap in limited literature on cellular metals.

Investigation of Mechanical Properties of Ti6Al4V Alloy Foams produced by Powder Metallurgy Method

In this study, it was aimed to production titanium alloy implants, which are widely used in the biomedical industry, as foamed materials under different mechanical alloying and sintering conditions using the powder metallurgy method Tİ6Al4V alloy is good mechanical properties, good biocompatibility properties and good corrosion resistance used as hard tissue replacements and implants. Similar mechanic properties with bone are expected from the implant to work coherently for long cycles of use and without any failure. Especially, elastic modulus of implant must be similar with bones, if not, some damages at bone surface and fallowing repeats of implant surgeries are reported. This situation has a destructive effect on health, finance, and comfort of the patient/user of the implant. In this study, powder metallurgy and space holder removal methods were used to produce porous Ti6Al4V specimens. Throughout the project study different space holder materials and binder agents were used. As weight percent, 20%, 30%, 40%, 60%, 70%, 80% porous specimens were pressed at uniaxial press machine, and sintered to the 850 ºC at argon atmosphere in furnace to reduce the oxidation to the level as low as possible. The E-Modulus values of the specimens reached the desired values with increasing porosity. It was obtained as 88 MPa in the specimen with 80% porosity, decreasing inversely proportionally, especially from the 60% porosity rate.

Accessible Ni‐Fe‐Oxalate Framework for Electrochemical Urea Oxidation with Radically Enhanced Kinetics

AbstractUrea oxidation reaction (UOR) has been utilized to substitute the oxygen evolution reaction (OER), to escalate the energy conversion efficiency in electrochemical hydrogen generation processes with denitrification of widespread urea in wastewater. This study reports breakthroughs in Ni‐based UOR electrocatalysts, particularly with NiFe oxalate (O‐NFF), derived from Ni3Fe alloy foam with prismatic nanostructures and elevated surface area. The O‐NFF achieves cutting‐edge performances, representing 500 mA cm−2 of current density at 1.47 V RHE and exceptionally low Tafel slope of 12.1 mV dec−1 (in 1 m KOH with 0.33 m urea). X‐ray photoelectron/absorption spectroscopy (XPS/XAS) coupled with density functional theory calculations unveil that oxalate ligands induce charge deficient Ni center, promoting stable urea‐O adsorption. Furthermore, Fe dopants enhance oxalate‐O charge density and H‐bond strength, facilitating C‐N cleavage for N2 and NO2− formation. The extraordinary UOR kinetics by the tandem effects of oxalate and Fe prevent Ni over‐oxidation, corroborated by operando XAS, minimizing OER interference. It agrees with an adaptive reconstruction to Fe‐doped β‐NiOOH on top surface in extended urea electrolysis with marginal loss in UOR kinetics. This findings shed light to bimetal‐organic‐framework as (pre)catalysts to improve industrial electrolytic H2 production.

The electrocatalytic self-reconstruction of ultrathin 2D MOF nanoarrays supported on alloy foam improves the oxygen evolution reaction

Investigating the self-reconstruction process of MOF-supported electrodes is of significant importance for understanding the reaction mechanisms in electrocatalytic oxygen evolution reaction (OER). By using 1,1′-ferrocenedicarboxylic acid (FcDA) as the ligand and NiFe foam (NFF) as the current collector, a self-supported T50NiFc-MOF/NFF electrode was synthesized through the introduction of triethylamine (TEA) to regulate the deprotonation process. The optimized T50NiFc-MOF/NFF exhibited excellent electrocatalytic OER performance, requiring only 217 mV to drive a current density of 10 mA cm−2, surpassing commercial RuO2. Additionally, the T50NiFc-MOF/NFF showed a remarkable electrocatalytic stability of over 70 h. The unique 2D MOF nanoarrays and strong coordination bonds between the metal and ligand in the as-prepared self-supported electrode contribute to the enrichment of electrochemical active sites and catalytic stability. Through a self-construction process, the 2D MOF nanoarrays on the electrode surface were in-situ converted into a more active metal-LDH during alkaline electrocatalysis, which played a crucial role in improving the electronic structure of the electrode, demonstrating its importance in achieving efficient OER processes.

Production, stability and properties of ultrafine MgAl2O4 (spinel) particles stabilized Mg–3Ca alloy foams

The present work reports the synthesis and mechanical behavior studies of Mg–3Ca alloy foams stabilized by ultrafine MgAl2O4 (spinel) particles. The MgAl2O4 particles was created in-situ in the Mg–3Ca alloy melt through the reaction of Mg, Al and O. Foaming was done by adding dolomite (CaMg(CO3)2) as blowing agent in the melt. The foaming behaviour was studied for different MgAl2O4 content in Mg–3Ca and holding times (10 and 15 min). The study reveals that the presence of MgAl2O4 significantly influences the foaming behavior of Mg–3Ca alloy resulting in equiaxed cell structure, uniform cell size distribution, higher expansion in comparison to the Mg–3Ca alloy foam which contains only MgO and CaO. An in-depth phase and microstructural analysis were performed to investigate the particles present in the gas-solid interface of the foam that contributes to foam stabilization. The quasi-static compression studies of foams exhibited better compressive strength (≈3–11 MPa) and energy absorption capacity (≈1.3–5.7 MJ/m3) in comparison to the Mg foams reported in the literature. The ductility of the Mg foams was also measured and compared with that of existing aluminium foams.

Lightweight and Highly Porous Ni-Ti Alloy Foams Synthesized by Powder Metallurgy using NaCl as Space Holder

Lightweight and Highly Porous Ni-Ti Alloy Foams Synthesized by Powder Metallurgy using NaCl as Space Holder

Effect of Mg Content Change on the Production of Closed-Cell Aluminum Alloy Foam by Selective Laser Melting

Effect of Mg Content Change on the Production of Closed-Cell Aluminum Alloy Foam by Selective Laser Melting

Highly Lithiophilic Oxidative Interfacial Layer for 3D Foam-Based Lithium Metal Anode: Lithium Impregnated Metal Foam Anode (LIMFA)

Numerous lithium-infused (or impregnated) lithium-metal anodes using pure Ni foams with excellent properties have been developed for use in Li batteries. However, pure Ni exhibits high reactivity with molten Li during infusion (e.g., coating, impregnation, etc.). Herein, a high-performance and ultra-stable (against molten Li) lithium-impregnated metal foam anode (LIMFA) is fabricated by a simple oxidation of nickel based alloy foam at 900 °C in air. A symmetric cell test employing the LIMFA anode showed stable stripping and plating performance. For thermal batteries without cup, LIMFA provided the highest reported specific capacity and first discharge of molten Li. After the cell discharge, the Ni based foam exhibited no Li leakage, surface damage, or structural collapse. Given these advantageous properties, in addition to its high specific capacity, LIMFA is expected to aid in the development of thermal batteries with enhanced performance.

Exploring damping behavior of novel polymer-derived aluminum alloy foam

Aluminum foams have excellent high-temperature damping capabilities. However, the use of metallic hydrides to synthesize foams reduces cell ductility, due to brittle intermetallics. This study demonstrates the damping behavior of AA2024 alloy foam synthesized using Polymethyl Hydrogen Siloxane as a foaming agent. Damping capacity was studied as a function of temperature (25 to 300 °C), frequency (1 to 80 Hz) and stress amplitude (1.5 to 21.5 MPa) using Dynamic Mechanical Analyzer. For comparison, monolithic samples of AA2024 at various conditions were also tested. The damping capacity of foams was about three times higher than the monolithic samples under certain conditions. The increased damping was a consequence of dislocation activity resulting from mode conversion around the numerous microscopic pores in the aluminum foam.

Nonlinear low-velocity impact response of sandwich beams with FG porous aluminum core reinforced by GPLs

Sandwich beam structures facing low-velocity impact frequently throughout their life cycle, making it necessary to investigate the impact response of these structures to enhance their design and reliability in service. In this paper, sandwich beam structures subjected to nonlinear low-velocity impacts are investigated, comprising a functionally graded (FG) porous aluminum core reinforced by graphene platelets (GPLs) and two aluminum alloy face sheets. The mechanical properties of FG-GPLRC core are predicted by a generalized Halpin-Tsai model, which takes porosity into account, where the material properties of the closed-cell aluminum alloy foam are established on experimental data. The numerical investigations are conducted using the finite element method and apply the Hertz contact law. The simulation results indicate that the FG-X pattern, where the porosity coefficients are designed to have the maximum values at the top and bottom layers, while to have the minimum values at the mid-plane layers, exhibits the best impact resistance, and that the incorporation of GPLs enhances the impact response. Furthermore, the findings suggest that the thickness of the core has no impact on the duration of the initial impact. Moreover, an increase in impactor velocity, density and radius results in an increase in both deflection and contact force.

Heterostructured Bimetallic MOF-on-MOF Architectures for Efficient Oxygen Evolution Reaction.

Electron modulation presents a captivating approach to fabricate efficient electrocatalysts for the oxygen evolution reaction (OER), yet it remains a challenging undertaking. In this study, an effective strategy is proposed to regulate the electronic structure of metal-organic frameworks (MOFs) by the construction of MOF-on-MOF heterogeneous architectures. As a representative heterogeneous architectures, MOF-74 on MOF-274 hybrids are in situ prepared on 3D metal substrates (NiFe alloy foam (NFF)) via a two-step self-assembly method, resulting in MOF-(74 + 274)@NFF. Through a combination of spectroscopic and theory calculation, the successful modulation of the electronic property of MOF-(74 + 274)@NFF is unveiled. This modulation arises from the phase conjugation of the two MOFs and the synergistic effect of the multimetallic centers (Ni and Fe). Consequently, MOF-(74 + 274)@NFF exhibits excellent OER activity, displaying ultralow overpotentials of 198 and 223mV at a current density of 10mA cm-2 in the 1.0 and 0.1M KOH solutions, respectively. This work paves the way for manipulating the electronic structure of electrocatalysts to enhance their catalytic activity.