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Cellular Metals: Fabrication, Properties and Applications
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Cellular Metals: Fabrication, Properties and Applications

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2020) | Viewed by 56386

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Isabel Duarte

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Guest Editor
Department of Mechanical Engineering, University of Aveiro, Campus Universitário de Santiago, 3810–193 Aveiro, Portugal
Interests: porous and cellular materials; foams; composite and nanocomposite foams; hybrid foams; graded cellular materials; foam-filled structures; manufacturing; physics of metal foaming; geometrical and mechanical characterisation; experimental tests; crashworthiness
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Matej Vesenjak

E-Mail Website
Guest Editor
Faculty of Mechanical Engineering, University of Maribor, Smetanova ul. 17, SI-2000 Maribor, Slovenia
Interests: porous and cellular materials; foams; geometrical and mechanical characterisation; experimental tests; computer simulations; finite element analysis; crashworthiness
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Thomas Fiedler

E-Mail Website
Guest Editor
School of Engineering, The University of Newcastle, Callaghan, NSW 22187, Australia
Interests: metallic syntactic foams; material characterization: physical, geometrical, mechanical, thermal, and corrosion; experimental and numerical analysis; manufacturing procedures
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Lovre Krstulović-Opara

E-Mail Website
Guest Editor
Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, University of Split, R. Boškovića 32, 21000 Split, Croatia
Interests: infrared thermography; material testing; cellular materials; non-destructive testing; metal structures design

Special Issue Information

Dear Colleagues,

It is our pleasure to invite you to submit a manuscript to a forthcoming Special Issue, “Cellular Metals: Fabrication, Properties and Applications”, in Metals (open access journal, Impact Factor: 1.704, https://www.mdpi.com/journal/metals).

Cellular solids and porous metals have become the most promising lightweight multifunctional materials, being used in a wide range of commercial, biomedical, industrial and military applications. This is due to the superior combination of properties derived from their porous cellular structures together with the excellent properties of the metals. In contrast with other cellular materials, the cellular metals are non-flammable, recyclable, extremely tough and are excellent energy absorbers.

This Special Issue is focused on:

  • recent advances in novel manufacturing methods of cellular metals,
  • design of new or improved performances of the cellular structures,
  • geometrical characterization and determination of physical properties,
  • experimental testing, numerical simulations and optimization methods,
  • applications.

We welcome contributions, including review manuscripts from experimentalists, theorists, and computational scientists in this research field.

Publication is subject to the usual conditions set forth by MDPI as the publisher of the journal. This includes the peer review process as well as publication fees. Details may be found on the journal’s website at https://www.mdpi.com/journal/metals.

Should you need any further information about this Special Issue, please do not hesitate to contact us.

Prof. Dr. Isabel Duarte
Prof. Dr. Matej Vesenjak
Prof. Dr. Thomas Fiedler
Prof. Dr.-Ing. Lovre Krstulović-Opara
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Stochastic and periodic cellular structures
  • composite and nanocomposite foams
  • hybrid and syntactic foams
  • open- and closed-cell foams
  • auxetic cellular structures
  • mechanical and thermal properties
  • manufacturing
  • experimental testing and computational simulations
  • application

Published Papers (17 papers)

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Editorial

Jump to: Research, Review

3 pages, 167 KiB  
Editorial
Cellular Metals: Fabrication, Properties and Applications
by Isabel Duarte, Thomas Fiedler, Lovre Krstulović-Opara and Matej Vesenjak
Metals 2020, 10(11), 1545; https://doi.org/10.3390/met10111545 - 20 Nov 2020
Cited by 2 | Viewed by 1708
Abstract
Cellular solids and porous metals have become some of the most promising lightweight multifunctional materials due to their superior combination of advanced properties mainly derived from their base material and cellular structure [...] Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)

Research

Jump to: Editorial, Review

9 pages, 4840 KiB  
Article
Influence of MWCNT Coated Nickel on the Foaming Behavior of MWCNT Coated Nickel Reinforced AlMg4Si8 Foam by Powder Metallurgy Process
by Ferdinandus Sarjanadi Damanik and Günther Lange
Metals 2020, 10(7), 955; https://doi.org/10.3390/met10070955 - 15 Jul 2020
Cited by 5 | Viewed by 2088
Abstract
This research studies the effect of multi-wall carbon nanotube (MWCNT) coated nickel to foaming time on the foam expansion and the distribution of pore sizes MWCNT reinforced AlMg4Si8 foam composite by powder metallurgy process. To control interface reactivity and wettability between MWCNT and [...] Read more.
This research studies the effect of multi-wall carbon nanotube (MWCNT) coated nickel to foaming time on the foam expansion and the distribution of pore sizes MWCNT reinforced AlMg4Si8 foam composite by powder metallurgy process. To control interface reactivity and wettability between MWCNT and the metal matrix, nickel coating is carried out on the MWCNT surface. Significantly, different foaming behavior of the MWCNT coated nickel reinforced AlMg4Si8 was studied with a foaming time variation of 8 and 9 min. Digital images generated by the imaging system are used with the MATLAB R2017a algorithm to determine the porosity of the surface and the pore area of aluminum foam efficiently. The results can have important implications for processing MWCNT coated nickel reinforced aluminum alloy composites. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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12 pages, 6086 KiB  
Article
Fabrication and Mechanical Properties of Rolled Aluminium Unidirectional Cellular Structure
by Matej Vesenjak, Masatoshi Nishi, Toshiya Nishi, Yasuo Marumo, Lovre Krstulović-Opara, Zoran Ren and Kazuyuki Hokamoto
Metals 2020, 10(6), 770; https://doi.org/10.3390/met10060770 - 09 Jun 2020
Cited by 3 | Viewed by 2452
Abstract
The paper focuses on the fabrication of novel aluminium cellular structures and their metallographic and mechanical characterisation. The aluminium UniPore specimens have been manufactured by rolling a thin aluminium foil with acrylic spacers for the first time. The novel approach allows for the [...] Read more.
The paper focuses on the fabrication of novel aluminium cellular structures and their metallographic and mechanical characterisation. The aluminium UniPore specimens have been manufactured by rolling a thin aluminium foil with acrylic spacers for the first time. The novel approach allows for the cheaper and faster fabrication of the UniPore specimens and improved welding conditions since a lack of a continuous wavy interface was observed in the previous fabrication process. The rolled assembly was subjected to explosive compaction, which resulted in a unidirectional aluminium cellular structure with longitudinal pores as the result of the explosive welding mechanism. The metallographic analysis confirmed a strong bonding between the foil surfaces. The results of the quasi-static and dynamic compressive tests showed stress–strain behaviour, which is typical for cellular metals. No strain-rate sensitivity could be observed in dynamic testing at moderate loading velocities. The fabrication process and the influencing parameters have been further studied by using the computational simulations, revealing that the foil thickness has a dominant influence on the final specimen geometry. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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15 pages, 1573 KiB  
Article
Hybrid Structures Made of Polyurethane/Graphene Nanocomposite Foams Embedded within Aluminum Open-Cell Foam
by Susana C. Pinto, Paula A. A. P. Marques, Romeu Vicente, Luís Godinho and Isabel Duarte
Metals 2020, 10(6), 768; https://doi.org/10.3390/met10060768 - 09 Jun 2020
Cited by 23 | Viewed by 4003
Abstract
This paper focuses on the development of hybrid structures containing two different classes of porous materials, nanocomposite foams made of polyurethane combined with graphene-based materials, and aluminum open-cell foams (Al-OC). Prior to the hybrid structures preparation, the nanocomposite foam formulation was optimized. The [...] Read more.
This paper focuses on the development of hybrid structures containing two different classes of porous materials, nanocomposite foams made of polyurethane combined with graphene-based materials, and aluminum open-cell foams (Al-OC). Prior to the hybrid structures preparation, the nanocomposite foam formulation was optimized. The optimization consisted of studying the effect of the addition of graphene oxide (GO) and graphene nanoplatelets (GNPs) at different loadings (1.0, 2.5 and 5.0 wt%) during the polyurethane foam (PUF) formation, and their effect on the final nanocomposite properties. Globally, the results showed enhanced mechanical, acoustic and fire-retardant properties of the PUF nanocomposites when compared with pristine PUF. In a later step, the hybrid structure was prepared by embedding the Al-OC foam with the optimized nanocomposite formulation (prepared with 2.5 wt% of GNPs (PUF/GNPs2.5)). The process of filling the pores of the Al-OC was successfully achieved, with the resulting hybrid structure retaining low thermal conductivity values, around 0.038 W∙m−1∙K−1, and presenting an improved sound absorption coefficient, especially for mid to high frequencies, with respect to the individual foams. Furthermore, the new hybrid structure also displayed better mechanical properties (the stress corresponding to 10% of deformation was improved in more than 10 and 1.3 times comparatively to PUF/GNPs2.5 and Al-OC, respectively). Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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16 pages, 67275 KiB  
Article
Comparative Study on the Uniaxial Behaviour of Topology-Optimised and Crystal-Inspired Lattice Materials
by Chengxing Yang, Kai Xu and Suchao Xie
Metals 2020, 10(4), 491; https://doi.org/10.3390/met10040491 - 08 Apr 2020
Cited by 11 | Viewed by 3685
Abstract
This work comparatively studies the uniaxial compressive performances of three types of lattice materials, namely face-centre cube (FCC), edge-centre cube (ECC), and vertex cube (VC), which are separately generated by topology optimisation and crystal inspiration. High similarities are observed between the materials designed [...] Read more.
This work comparatively studies the uniaxial compressive performances of three types of lattice materials, namely face-centre cube (FCC), edge-centre cube (ECC), and vertex cube (VC), which are separately generated by topology optimisation and crystal inspiration. High similarities are observed between the materials designed by these two methods. The effects of design method, cell topology, and relative density on deformation mode, mechanical properties, and energy absorption are numerically investigated and also fitted by the power law. The results illustrate that both topology-optimised and crystal-inspired lattices are mainly dominated by bending deformation mode. In terms of collapse strength and elastic modulus, VC lattice is stronger than FCC and ECC lattices because its struts are arranged along the loading direction. In addition, the collapse strength and elastic modulus of the topology-optimised FCC and ECC are close to those generated by crystal inspiration at lower relative density, but the topology-optimised FCC and ECC are obviously superior at a higher relative density. Overall, all topology-generated lattices outperform the corresponding crystal-guided lattice materials with regard to the toughness and energy absorption per unit volume. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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13 pages, 5032 KiB  
Article
Stabilization Mechanism of Semi-Solid Film Simulating the Cell Wall during Fabrication of Aluminum Foam
by Takashi Kuwahara, Akira Kaya, Taro Osaka, Satomi Takamatsu and Shinsuke Suzuki
Metals 2020, 10(3), 333; https://doi.org/10.3390/met10030333 - 02 Mar 2020
Cited by 6 | Viewed by 2713
Abstract
Semi-solid route is a fabrication method of aluminum foam where the melt is thickened by primary crystals. In this study, semi-solid aluminum alloy films were made to observe and evaluate the stabilization mechanism of cell walls in Semi-solid route. Each film was held [...] Read more.
Semi-solid route is a fabrication method of aluminum foam where the melt is thickened by primary crystals. In this study, semi-solid aluminum alloy films were made to observe and evaluate the stabilization mechanism of cell walls in Semi-solid route. Each film was held at different solid fractions and holding times. In lower solid fractions, as the holding time increases, the remaining melt in the films lessens and this could be explained by Poiseuille flow. However, the decreasing tendency of the remaining melt in the films lessens as the solid fraction increases. Moreover, when the solid fraction is high, decreasing tendency was not observed. These are because at a certain moment, clogging of primary crystals occurs under the thinnest part of the film and drainage is largely suppressed. Moreover, clogging is occurring in solid fraction of 20–45% under the thinnest part of the film. Moreover, the time to occur clogging becomes earlier as the solid fraction increases. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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18 pages, 7078 KiB  
Article
The Influence of Alloy Composition and Liquid Phase on Foaming of Al–Si–Mg Alloys
by Francisco García-Moreno, Laurenz Alexander Radtke, Tillmann Robert Neu, Paul Hans Kamm, Manuela Klaus, Christian Matthias Schlepütz and John Banhart
Metals 2020, 10(2), 189; https://doi.org/10.3390/met10020189 - 28 Jan 2020
Cited by 15 | Viewed by 3156
Abstract
The foaming behaviour of aluminium alloys processed by the powder compaction technique depends crucially on the exact alloy composition. The AlSi8Mg4 alloy has been in use for a decade now, and it has been claimed that this composition lies in an “island of [...] Read more.
The foaming behaviour of aluminium alloys processed by the powder compaction technique depends crucially on the exact alloy composition. The AlSi8Mg4 alloy has been in use for a decade now, and it has been claimed that this composition lies in an “island of good foaming”. We investigated the reasons for this by systematically studying alloys around this composition by varying the Mg and Si content by a few percent. We applied in situ X-ray 2D and 3D imaging experiments combined with a quantitative nucleation number and expansion analysis, X-ray tomography of solid foams to assess the pore structure and pore size distribution, and in situ diffraction experiments to quantify the melt fraction at any moment. We found a correlation between melt fraction and expansion height and verified that the “island of good foaming” actually exists, and foams outside a preferred range for the liquid fraction—just above TS and between 40–60%—show a poorer expansion performance than the reference alloy AlSi8Mg4. A very slight increase of Si and decrease of Mg content might further improve this foam. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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34 pages, 17384 KiB  
Article
Effects of Eutectic Modification and Grain Refinement on Microstructure and Properties of PM AlSi7 Metallic Foams
by Dirk Lehmhus, Daniela Hünert, Ulrike Mosler, Ulrich Martin and Jörg Weise
Metals 2019, 9(12), 1241; https://doi.org/10.3390/met9121241 - 20 Nov 2019
Cited by 10 | Viewed by 3348
Abstract
For AlSi7 foams, microstructure modification by variation of solidification rates and addition of Sr, B and TiB2/TiAl3 was investigated and its transfer to powder metallurgical metal foaming processes demonstrated. Microstructural characterization focused on grain size and morphology of the eutectic [...] Read more.
For AlSi7 foams, microstructure modification by variation of solidification rates and addition of Sr, B and TiB2/TiAl3 was investigated and its transfer to powder metallurgical metal foaming processes demonstrated. Microstructural characterization focused on grain size and morphology of the eutectic phase. Cooling rates during solidification were linked to secondary dendrite arm spacing, establishing a microstructure-based measure of solidification rates. Effects of refining and modification treatments were compared and their influence on foam expansion evaluated. Studies on foams focused on comparison of micro- and pore structure using metallographic techniques as well as computed tomography in combination with image analysis. Reference samples without additives and untreated as well as annealed TiH2 as foaming agent allowed evaluation of pore and microstructure impact on mechanical performance. Evaluation of expansion and pore structure revealed detrimental effects of Sr and B additions, limiting the evaluation of mechanical performance to the TiB2 samples. These, as well as the two reference series samples, were subjected to quasi-static compression testing. Stress-strain curves were gained and density-dependent expressions of ultimate compressive strength, plateau strength and tangent modulus derived. Weibull evaluation of density-normalized mechanical properties revealed a significant influence of grain size on the Weibull modulus at densities below 0.4 g/cm3. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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17 pages, 7900 KiB  
Article
Mechanical, Thermal, and Acoustic Properties of Aluminum Foams Impregnated with Epoxy/Graphene Oxide Nanocomposites
by Susana C. Pinto, Paula A.A.P. Marques, Matej Vesenjak, Romeu Vicente, Luís Godinho, Lovre Krstulović-Opara and Isabel Duarte
Metals 2019, 9(11), 1214; https://doi.org/10.3390/met9111214 - 12 Nov 2019
Cited by 15 | Viewed by 3273
Abstract
Hybrid structures with epoxy embedded in open-cell aluminum foam were developed by combining open-cell aluminum foam specimens with unreinforced and reinforced epoxy resin using graphene oxide. These new hybrid structures were fabricated by infiltrating an open-cell aluminum foam specimen with pure epoxy or [...] Read more.
Hybrid structures with epoxy embedded in open-cell aluminum foam were developed by combining open-cell aluminum foam specimens with unreinforced and reinforced epoxy resin using graphene oxide. These new hybrid structures were fabricated by infiltrating an open-cell aluminum foam specimen with pure epoxy or mixtures of epoxy and graphene oxide, completely filling the pores. The effects of graphene oxide on the mechanical, thermal, and acoustic performance of epoxy/graphene oxide-based nanocomposites are reported. Mechanical compression analysis was conducted through quasi-static uniaxial compression tests at two loading rates (0.1 mm/s and 1 mm/s). Results show that the thermal stability and the sound absorption coefficient of the hybrid structures were improved by the incorporation of the graphene oxide within the epoxy matrix. However, the incorporation of the graphene oxide into the epoxy matrix can create voids inside the epoxy resin, leading to a decrease of the compressive strength of the hybrid structures, thus no significant increase in the energy absorption capability was observed. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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11 pages, 2692 KiB  
Article
Elasto-Plastic Behaviour of Transversely Isotropic Cellular Materials with Inner Gas Pressure
by Zhimin Xu, Kangpei Meng, Chengxing Yang, Weixu Zhang, Xueling Fan and Yongle Sun
Metals 2019, 9(8), 901; https://doi.org/10.3390/met9080901 - 16 Aug 2019
Cited by 3 | Viewed by 3629
Abstract
The fabrication process of cellular materials, such as foaming, usually leads to cells elongated in one direction, but equiaxed in a plane normal to that direction. This study is aimed at understanding the elasto-plastic behaviour of transversely isotropic cellular materials with inner gas [...] Read more.
The fabrication process of cellular materials, such as foaming, usually leads to cells elongated in one direction, but equiaxed in a plane normal to that direction. This study is aimed at understanding the elasto-plastic behaviour of transversely isotropic cellular materials with inner gas pressure. An idealised ellipsoidal-cell face-centred-cubic foam that is filled with gas was generated and modelled to obtain the uniaxial stress–strain relationship, Poisson’s ratio and multiaxial yield surface. The effects of the elongation ratio and gas pressure on the elasto-plastic properties for a relative density of 0.5 were investigated. It was found that an increase in the elongation ratio caused increases in both the elastic modulus and yield stress for uniaxial loading along the cell elongation direction, and led to a tilted multiaxial yield surface in the mean stress and Mises equivalent stress plane. Compared to isotropic spheroidal-cell foams, the size of the yield surface of the ellipsoidal-cell foam is smaller for high-stress triaxiality, but larger for low-stress triaxiality, and the yield surface rotates counter-clockwise with the Lode angle increasing. The gas pressure caused asymmetry of the uniaxial stress–strain curve (e.g., reduced tensile yield stress), and it increased the nominal plastic Poisson’s ratio for compression, but had the opposite effect for tension. Furthermore, the gas pressure shifted the yield surface towards the negative mean stress axis with a distance equal to the gas pressure. The combined effects of the elongation ratio and gas pressure are complicated, particularly for the elasto-plastic properties in the plane in which the cells are equiaxed. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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17 pages, 5504 KiB  
Article
Optimization and Validation of Sound Absorption Performance of 10-Layer Gradient Compressed Porous Metal
by Fei Yang, Xinmin Shen, Panfeng Bai, Xiaonan Zhang, Zhizhong Li and Qin Yin
Metals 2019, 9(5), 588; https://doi.org/10.3390/met9050588 - 21 May 2019
Cited by 17 | Viewed by 3177
Abstract
Sound absorption performance of a porous metal can be improved by compression and optimal permutation, which is favorable to promote its application in noise reduction. The 10-layer gradient compressed porous metal was proposed to obtain optimal sound absorption performance. A theoretical model of [...] Read more.
Sound absorption performance of a porous metal can be improved by compression and optimal permutation, which is favorable to promote its application in noise reduction. The 10-layer gradient compressed porous metal was proposed to obtain optimal sound absorption performance. A theoretical model of the sound absorption coefficient of the multilayer gradient compressed porous metal was constructed according to the Johnson-Champoux-Allard model. Optimal parameters for the best sound absorption performance of the 10-layer gradient compressed porous metal were achieved by a cuckoo search algorithm with the varied constraint conditions. Preliminary verification of the optimal sound absorber was conducted by the finite element simulation, and further experimental validation was obtained through the standing wave tube measurement. Consistencies among the theoretical data, the simulation data, and the experimental data proved accuracies of the theoretical sound absorption model, the cuckoo search optimization algorithm, and the finite element simulation method. For the investigated frequency ranges of 100–1000 Hz, 100–2000 Hz, 100–4000 Hz, and 100–6000 Hz, actual average sound absorption coefficients of optimal 10-layer gradient compressed porous metal were 0.3325, 0.5412, 0.7461, and 0.7617, respectively, which exhibited the larger sound absorption coefficients relative to those of the original porous metals and uniform 10-layer compressed porous metal with the same thickness of 20 mm. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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13 pages, 4531 KiB  
Article
Automated Continuous Production Line of Parts Made of Metallic Foams
by Isabel Duarte, Matej Vesenjak and Manuel J. Vide
Metals 2019, 9(5), 531; https://doi.org/10.3390/met9050531 - 08 May 2019
Cited by 28 | Viewed by 3332
Abstract
The paper presents an automated continuous production line (7 m × 1.5 m × 1 m) of high-quality metallic foams using a powder metallurgical method. This continuous production line was used to obtain metal foam parts and/or components by heating the foamable precursor [...] Read more.
The paper presents an automated continuous production line (7 m × 1.5 m × 1 m) of high-quality metallic foams using a powder metallurgical method. This continuous production line was used to obtain metal foam parts and/or components by heating the foamable precursor material at melting temperatures close to the temperature of the metallic matrix and cooling the formed liquid metallic foam (in liquid state), which then results in a solid closed-cell metallic foam. This automated continuous production line is composed of a continuous foaming furnace, a cooling sector and a robotic system. This installation has enabled a technological breakthrough with many improvements solving some technical problems and eliminating the risks and dangers related to the safety of workers due to the high temperatures involved in this process. The whole process becomes automatic without any need for human intervention. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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15 pages, 7130 KiB  
Article
Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route
by Takashi Kuwahara, Taro Osaka, Mizuki Saito and Shinsuke Suzuki
Metals 2019, 9(2), 153; https://doi.org/10.3390/met9020153 - 29 Jan 2019
Cited by 9 | Viewed by 3469
Abstract
A2024 alloy foams were fabricated by two methods. In the first method, the melt was thickened by Mg, which acts as an alloying element (melt route). In the second method, the melt was thickened by using primary crystals at a semi-solid temperature with [...] Read more.
A2024 alloy foams were fabricated by two methods. In the first method, the melt was thickened by Mg, which acts as an alloying element (melt route). In the second method, the melt was thickened by using primary crystals at a semi-solid temperature with a solid fraction of 20% (semi-solid route). A2024 alloy foams fabricated through the semi-solid route had coarse and uneven pores. This led to slightly brittle fracture of the foams, which resulted in larger energy absorption efficiency than that of the foams fabricated through the melt route. Moreover, A2024 alloy foams fabricated through the semi-solid route had a coarser grain size because of the coarse primary crystals. However, by preventing the decrease in the alloying element Mg, the θ/θ’ phase was suppressed. Additionally, by preventing the precipitation of the S′ phase, the amount of Guinier-Preston-Bagaryatsky (GPB) zone increased. This resulted in a larger plateau stress. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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11 pages, 3222 KiB  
Article
Aluminum Foam-Filled Steel Tube Fabricated from Aluminum Burrs of Die-Castings by Friction Stir Back Extrusion
by Yoshihiko Hangai, Ryusei Kobayashi, Ryosuke Suzuki, Masaaki Matsubara and Nobuhiro Yoshikawa
Metals 2019, 9(2), 124; https://doi.org/10.3390/met9020124 - 24 Jan 2019
Cited by 9 | Viewed by 3503
Abstract
A mixture of Al burrs of Al high-pressure die-castings and a blowing agent powder was used to fabricate Al foam-filled steel tubes by friction stir back extrusion (FSBE). It was shown that the mixture can be sufficiently consolidated to form an Al precursor [...] Read more.
A mixture of Al burrs of Al high-pressure die-castings and a blowing agent powder was used to fabricate Al foam-filled steel tubes by friction stir back extrusion (FSBE). It was shown that the mixture can be sufficiently consolidated to form an Al precursor that is coated on the inner surface of a steel tube by the plastic flow generated during FSBE. Namely, a precursor coated steel tube can be fabricated from Al burrs by FSBE. By heat treatment of the precursor coated steel tube, an Al foam-filled steel tube can be fabricated. Al foam was sufficiently filled in the steel tube, and the porosity was almost homogeneously distributed in the entire sample. In compression tests of the samples, the Al foam-filled steel tube fabricated from Al burrs exhibited similar compression properties to an Al foam-filled steel tube fabricated from the bulk Al precursor. Consequently, it was shown that an Al foam-filled steel tube cost-effectively fabricated from Al burrs by FSBE compares favorably with an Al foam-filled steel tube fabricated from the bulk Al precursor. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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15 pages, 6258 KiB  
Article
A-242 Aluminium Alloy Foams Manufacture from the Recycling of Beverage Cans
by Nallely Montserrat Trejo Rivera, Jesús Torres Torres and Alfredo Flores Valdés
Metals 2019, 9(1), 92; https://doi.org/10.3390/met9010092 - 16 Jan 2019
Cited by 12 | Viewed by 4029
Abstract
This paper presents and discusses a methodology implemented to study the process of the preparation of aluminium alloy foams using the alloy A-242, beginning from the recycling of secondary aluminium obtained from beverage cans. The foams are prepared by a melting process by [...] Read more.
This paper presents and discusses a methodology implemented to study the process of the preparation of aluminium alloy foams using the alloy A-242, beginning from the recycling of secondary aluminium obtained from beverage cans. The foams are prepared by a melting process by adding 0.50 wt.% calcium to the A-242 aluminium alloy with the aim to change its viscosity in the molten state. To obtain the foam, titanium hydride is added in different concentrations (0.50 wt.%, 0.75 wt.%, and 1.00 wt.%) and at different temperatures (923, 948 K, and 973 K) while the foaming time is kept constant at 30 s. For a set of experimental parameter values, aluminium alloy foams with the average relative density of 0.12 were obtained and had an 88.22% average porosity. In this way, it is possible to state that the preparation of aluminium alloy foams A-242 processed from the recycling of cans is possible, with characteristics and properties similar to those obtained using commercial-purity metals. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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12 pages, 10761 KiB  
Article
Effect of Primary Crystals on Pore Morphology during Semi-Solid Foaming of A2024 Alloys
by Takashi Kuwahara, Mizuki Saito, Taro Osaka and Shinsuke Suzuki
Metals 2019, 9(1), 88; https://doi.org/10.3390/met9010088 - 16 Jan 2019
Cited by 6 | Viewed by 3459
Abstract
We investigated pore formation in aluminum foams by controlling primary crystal morphology using three master alloys. The first one was a direct chill cast A2024 (Al-Cu-Mg) alloy (DC-cast alloy). The others were A2024 alloys prepared to possess fine spherical primary crystals. The second [...] Read more.
We investigated pore formation in aluminum foams by controlling primary crystal morphology using three master alloys. The first one was a direct chill cast A2024 (Al-Cu-Mg) alloy (DC-cast alloy). The others were A2024 alloys prepared to possess fine spherical primary crystals. The second alloy was made by applying compressive strain through a Strain-Induced Melt-Activated process alloy (SIMA alloy). The third one was a slope-cast A2024 alloy (slope-cast alloy). Each alloy was heated to either 635 °C (fraction of solid fs = 20%) or 630 °C (fs = 40%). TiH2 powder was added to the alloys as a foaming agent upon heating them to a semi-solid state and they were stirred while being held in the furnace. Subsequently, A2024 alloy foams were obtained via water-cooling. The primary crystals of the DC-cast alloy were coarse and irregular before foaming. After foaming, the size of the primary crystals remained irregular, but also became spherical. The SIMA and slope-cast alloys possessed fine spherical primary crystals before and after foaming. In addition to average-sized pores (macro-pores), small pores were observed inside the cell walls (micro-pores) of each alloy. The formation of macro-pores did not depend on the formation of the primary crystals. Only in the DC-cast alloy did fine micro-pores exist within the primary crystals. The number of micro-pores in the SIMA and slope-cast alloys was one third of that in the DC-cast alloy. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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Review

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18 pages, 3053 KiB  
Review
Brief Review on Experimental and Computational Techniques for Characterization of Cellular Metals
by Isabel Duarte, Thomas Fiedler, Lovre Krstulović-Opara and Matej Vesenjak
Metals 2020, 10(6), 726; https://doi.org/10.3390/met10060726 - 30 May 2020
Cited by 12 | Viewed by 3345
Abstract
The paper presents a brief review of the main experimental and numerical techniques and standards to investigate and quantify the structural, mechanical, thermal, and acoustic properties of cellular metals. The potential of non-destructive techniques, such as X-ray computed tomography and infrared thermography are [...] Read more.
The paper presents a brief review of the main experimental and numerical techniques and standards to investigate and quantify the structural, mechanical, thermal, and acoustic properties of cellular metals. The potential of non-destructive techniques, such as X-ray computed tomography and infrared thermography are also presented. Full article
(This article belongs to the Special Issue Cellular Metals: Fabrication, Properties and Applications)
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