Aluminum Alloy Foam Research Articles

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.

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.

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

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.

Effect of Heating Temperature, Holding Time and Stabilization Temperature on the Al-Foam Properties

The interest in metallic foam is increasing since their cellular structures have a unique combination of properties such as high stiffness, low density, lightweight, high specific strength, and thermal insulation. Commonly, the performance of metallic foam can be improved by the heat treatment process. However, the previous heat treatment methods still present the brittle crack path and the research on heat treatments of the metal foam properties is very limited. In this study, individual parameters in stress relieving treatment that contribute to Al-Foam properties were investigated. The stress-relieving process of the samples was performed using a vacuum furnace. The composition of aluminium foam was determined by X-Ray Fluorescence (XRF). The hardness test was conducted using a microhardness tester. Quasi-static compression test was conducted by a universal testing machine. From the SEM-EDX elemental images, it can be observed that traces of Ca, Fe, Ti, and Si have a homogeneous distribution in the Al-matrix. In the result obtained, the mechanical properties of aluminium alloy foam decrease when the heating temperature is enhanced. The mechanical properties of closed-cell aluminium alloy increase with the reduction of the holding temperature. This was due to the recovery and recrystallization process which depended on time and temperature during the heat treatment process. The mechanical properties of aluminium foam were raised after increasing the stabilization temperature. This finding was due to the vibrational atomic motion in the recovery process.

Characteristics of Pore Morphology in Aluminum Alloy Foams Fabricated by Semi-Solid Route among Multiple Experimental Runs

A semi-solid route is expected to be a fabrication method that can fabricate aluminum alloy foams with a variety of mechanical properties, but the allowance fluctuation of the fabrication conditions of aluminum alloy foams with high reproducibility is not clear. The objective of this study was to reveal the allowance fluctuation between the setting temperature and the actual temperature of the melt to fabricate stable foams, having pores with small pores and high circularity, and the influence of the increasing volume fraction of the solid on the pore morphology. Al-Si alloy foams were fabricated five times by adding a blowing agent into a semi-solid slurry under the same setting fabrication conditions, such as the temperature and concentration of oxygen in the atmosphere. The results of small relative standard deviations of pore diameter and circularity indicated that the conducted fabrication process had high reproducibility, even if the volume fraction of the solid changed in a range of 5%. When the volume fraction of the solid exceeds the minimal fraction of primary crystals for prevention of drainage, the clogging effect works more efficiently because the ratio of clogged cell walls increases. Additionally, the preferred range of the volume fraction of the solid for the fabrication of stable foam was revealed to be around 15% to 35%.

Effect of Ti content on the cell structure and compressive and energy absorption properties of Al3Ti/Al6061 foam composite

Aluminium alloy foams are often used as cushioning parts for automobiles because of their excellent energy absorption properties and lightweight characteristics. Their energy absorption properties mainly depend on the cell structure of the foam, but the cell structure of aluminium alloy foams prepared by the powder metallurgy method is usually difficult to control. In this work, Al3Ti/Al6061 foam composite (AT-FC) was prepared by powder metallurgy using TiH2 as the blowing agent and a mixture of Al6061 and Ti powder as the foaming matrix. The effects of different Ti contents on the cell structure, cell distribution and morphology of AT-FC were focused on, and their mechanical properties under quasi-static compressive loading were investigated. The experimental results showed that different Ti contents could regulate the cell size and improve the cell morphology and distribution, in which AT-FC contains 7.5 wt% Ti had the best cell structure with an average cell size of about 1.56 mm and an average circularity of 0.82. By comparing the compressive yield strength, energy absorption and specific energy absorption of AT-FC with different Ti contents, the AT-FC with 10 wt% Ti had the best compressive yield strength of 8.96 MPa and AT-FC with 7.5 wt% Ti had the best energy absorption of 6.50MJ/m3.

Microstructural characteristics and mechanical properties of 7075 aluminum alloy foam sandwich panels fabricated via integrated forming and foaming

A new integrated forming and foaming method based on friction stir welding (FSW) was proposed for foam sandwich panels. The microstructure characteristics of the precursors and foams with different welding parameters were analyzed using optical microscopy and scanning electron microscope (SEM/EDS). The temperature field and flow field of foam precursor joint in FSW were simulated by Fluent CFD software. The microstructural characteristics of foam precursor after hot forming were analyzed using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The effect of foam precursor deformation on foam evolution was also investigated. The results show that the formability of foam precursor is the same as that of rolled plate. Aluminum foam sandwich panel with homogenous pore structure is prepared at 680 °C for 225 s. After hot forming, the equiaxed recrystallized grain is obtained, and the dislocation and the second phase provide reinforcement. In addition, Rgoss{110}〈110〉 texture component strength increases. When the tensile strain is 0.15, smaller and more uniform pores are produced. Numerical simulations show that the peak temperature gradually decreases with the increase of the distance of the stirring head center. In addition, the temperature on the advancing side (AS) is higher than that on the retreating side (RS). When the tool travel speed is 50 mm/min and rotational speed is 2000 r/min, the maximum material flow velocity at the joint section is 184.2 mm/s and the highest concentration of powder tracing particles is 0.0123 kg/m3. It is proved that the integrated forming and foaming method can solve the problem in manufacturing of complex curved AFS components.

Production of Refined and Modified Closed-Cell Aluminum Foams by Melt-Foaming Method

Closed-cell A356 aluminum alloy foams refined and modified were successfully fabricated by using barite and calcium carbonate as thickening and foaming agents, respectively. A melt treatment consisting of adding master alloys of Al-5Ti-1B and Al-10Sr for refining the dendritic microstructure and modifying the primary eutectic silicon, respectively, were included in the foaming process. The microstructure and mechanical properties of the foams manufactured were analyzed and compared with foams produced without the refining and modifying treatments. The secondary dendritic arm spacing (SDAS) was determined by optical measurements. Lower SDAS values were obtained in foam regions closer to the mold walls due to the high solidification rate imposed during the cooling step and a decrease in the SDAS values for the foams produced with the addition of the Al-5Ti-1B master alloy was evident. Additionally, the addition of the Al-10Sr master alloy caused the formation of solid solution dendrites and a fine irregular fibrous form of silicon. Foams produced with the melt treatment exhibit a good combination of structure and mechanical properties. Therefore, the melt route established is a feasible way to improve foam performance where the lowest SDAS and the highest mechanical properties were obtained for the closed-cell foams produced.

Energy Transfer Efficiency Based Nonlinear Ultrasonic Testing Technique for Debonding Defects of Aluminum Alloy Foam Sandwich Panels

In order to improve the accuracy of detection results of debonding defects of aluminum alloy thin plate, the nonlinear ultrasonic technology is used to detect the simulated defect samples, aiming at problems such as near surface blind region caused by the interaction of incident wave, reflected wave and even second harmonic wave in a short time due to the small thickness of thin plates. An integral method based on energy transfer efficiency is proposed to calculate the nonlinear ultrasonic coefficient to characterize the debonding defects of thin plates. A series of simulated debonding defects of different sizes were made using aluminum alloy plates with four thicknesses of 1 mm, 2 mm, 3 mm and 10 mm. By comparing the traditional nonlinear coefficient with the integral nonlinear coefficient proposed in this paper, it is verified that both methods can quantitatively characterize the size of debonding defects. The nonlinear ultrasonic testing technology based on energy transfer efficiency has higher testing accuracy for thin plates.

Experimental study on the impact resistance of hollow thin-walled aluminum alloy tubes and foam-filled aluminum tubes (6063-T5)

This paper presents a study on the axial impact resistance of hollow thin-walled aluminum alloy tubes and aluminum foam-filled thin-walled tubes. 15 hollow thin-walled aluminum alloy tubes and 15 thin-walled aluminum alloy tubes filled with aluminum foam were tested under drop hammer impacts. The process of the impact, the failure modes of the specimens, the time history curves of impact forces, and the vertical deflections were recorded in the test. The effects of impact velocity, aluminum alloy wall thickness, cross-sectional width, and aluminum foam on the performance of the hollow and aluminum foam-filled thin-walled aluminum alloy tubes were discussed. In addition, a finite element model was established to simulate the test considering the strain rate effect of aluminum alloy and aluminum foam. The results showed that both hollow and foam-filled thin-walled aluminum alloy tubes were damaged to different degrees. Under the same impact energy, the damage of the foam-filled thin-walled aluminum alloy tube was less severe than that of the hollow thin-walled aluminum alloy tube; under the axial impact load of the drop hammer, the most effective way to improve the impact resistance of the hollow and foam-filled thin-walled aluminum alloy tubes was to increase the wall thickness of the outer thin-walled aluminum alloy tube, while the effect of increasing the cross-sectional size of the outer thin-walled aluminum alloy tube on the impact resistance of the specimen is less significant. The peak impact force, vertical deflection and the duration of impact forces are most sensitive to the impact velocity.

Analyzing the influence of the investment casting process parameters on microstructure and mechanical properties of open-pore Al–7Si foams

Aluminum alloy foams with high specific compressive strength and good energy absorption capacity are widely used as structural materials and shock absorbers. The investment casting process offers an interesting opportunity for the production of open-pore aluminum foams. However, foam casting differs from casting of solid parts, and there is a lack of practical knowledge about the microstructure tuning of the ultra-thin cast struts. Our study focuses on the influences of the casting conditions such as mold temperature on the microstructure and consequently on the mechanical properties of aluminum-silicon alloy foams. We investigated microstructural features using various metallography techniques and defined mechanical properties under uniaxial compression test. Here, we observed improvements in the strut microstructure together with decrease of the mold filling by reduction of the mold temperature. Microstructure improvements involve transformation of a single dendritic aluminum grain in each strut to globular grains along with a more homogeneous distribution of the silicon particles across the strut cross-section. These changes bring higher ductility and energy absorption efficiency to the foams, which are evident from the smoother plateau of the stress-strain curves. Decline of the mold filling, on the other hand, has negative effect on the overall mechanical properties.

Quasistatic deformation analysis of melt-based molded die-cast open-cell aluminum alloy foam

Quasistatic deformation analysis of melt-based molded die-cast open-cell aluminum alloy foam

Effect of Laser Forming on the Fatigue Behavior of Metal Foams

Abstract Metal foam is an excellent lightweight material with promising industrial applications. Laser forming has been studied and shown to be a viable non-contact method to shape metal foam panels into desired geometry without fracturing the foam’s cellular structure. However, whether laser forming alters the fatigue performance of metal foam has not been well understood. This study focuses on the tension-to-tension fatigue behavior of closed-cell metal foam before and after laser forming. Fatigue tests were conducted at different load levels on as-received and laser treated aluminum alloy foam with two different scanning patterns. Fatigue life were comparably tested and subsequently investigated, and fracture surface was closely examined to relate to the fluctuation in fatigue life and varying data scatter of fatigue life between as-received and laser formed specimen. Numerical models with equivalent foam geometry were used to investigate the strain distribution after laser forming, and helped to elucidate the fatigue life improvement after laser forming. Fatigue simulations where foam structure approximated with regular Kelvin cell was conducted demonstrate the effect of stress concentration on fatigue life. Generally, laser forming resulted in an improvement in fatigue performance of the aluminum alloy foam.

Low-cycle fatigue assessment of open-cell A332 aluminum alloy foams

Though metal foams are used in applications where they could be exposed to cyclic loading, their fatigue strengths also must be evaluated concerning this fact that these materials have much lower resistance to cyclic loads than their base bulk materials. In this study, the open cell foam specimens which are produced by A332 aluminum alloy stir casting and solidification under pressure, are subjected to force-controlled cyclic compressive loading. Experiments revealed that the produced foams have a good capacity for fatigue loading so that in the range of stress range below 90% of corresponding yield stress, almost no low-cycle fatigue occurs.

Aluminium foam with sub-mm sized cells produced using a rotating gas injector

Closed-cell solid aluminium alloy foams should ideally contain small and equally sized cells for the sake of better and more predictable mechanical properties, but real foams generated by injection of gas into melts usually exhibit a broad distribution of cell sizes and shapes. Here we investigate how gas bubbles in an aluminium alloy melt containing stabilizing SiC particles can be created in a controlled way by letting the injector move on a circular orbit through the melt at different velocities and adapting the gas flow. The structures of the resulting solidified foams are characterized by X-ray tomography. We identify conditions that allow us to obtain near-monodisperse foams with cell sizes below 1 mm and are able to reduce the content of SiC particles from the usual 20 vol% to 8 vol%.

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.