Metals

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11 pages, 6403 KiB

Open AccessArticle

Foaming Behavior of Microsized Aluminum Foam Using Hot Rolling Precursor

by Fang Wang, Yuqing Bian, Lucai Wang and Wenzhan Huang

Metals 2023, 13(5), 928; https://doi.org/10.3390/met13050928 - 10 May 2023

Cited by 1 | Viewed by 1053

Aluminum foam that is lightweight with high specific strength, high energy absorption and other characteristics can be used in aerospace, transportation, machinery manufacturing and other fields. The PCM method is usually used to prepare closed-cell aluminum foams. The microsized aluminum foams made by [...] Read more.

Aluminum foam that is lightweight with high specific strength, high energy absorption and other characteristics can be used in aerospace, transportation, machinery manufacturing and other fields. The PCM method is usually used to prepare closed-cell aluminum foams. The microsized aluminum foams made by this process can solve the non-uniform pore structures caused by liquid drainage during the foaming process of large aluminum foams. The surface morphology and internal pore structure of microsized aluminum foams are affected by the quality of the precursor used for foaming. In this paper, foamable precursors were obtained via either hot rolling or hot extrusion and subsequently foamed. By analyzing the micromorphology and foaming process of the precursor, the influence of the technological method on the macroscopic pore structure of the final aluminum foam was studied. The results show that the aluminum powder particles in the precursor prepared with the hot rolling method had metallurgical bonding, and the outer surface was dense, with almost no porosity and holes in the interior. The microsized aluminum foam obtained after foaming was smooth in appearance, and the internal pore structure was round and uniform. The reason is that during the foaming process of microsize aluminum foam, the foaming agent was evenly distributed in the precursor of the hot rolling process because of its compact structure. During the foaming process, the decomposed gas of the foaming agent will not escape, and the evenly distributed foaming agent tends to nucleate in situ. In the process of rapid foaming, the pressure in the bubble is enough to resist the liquid drainage phenomenon caused by gravity, and the growth direction of the gas core is isotropic, which promotes the foam structure to be more rounded and uniform. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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12 pages, 6437 KiB

Open AccessArticle

Preparation and Heat Dissipation Properties Comparison of Al and Cu Foam

by Yao Huang, Zexin Li, Lucai Wang, Leilei Sun, Xiaohong You, Wenzhan Huang and Fang Wang

Metals 2022, 12(12), 2066; https://doi.org/10.3390/met12122066 - 30 Nov 2022

Viewed by 1189

Abstract

The space holder method, a kind of powder metallurgy method which can avoid the process of melting metal to prepare metal foams, has particular significance in solving the difficulty of preparing metal foams with high melting points. In this paper, Na₂S [...] Read more.

The space holder method, a kind of powder metallurgy method which can avoid the process of melting metal to prepare metal foams, has particular significance in solving the difficulty of preparing metal foams with high melting points. In this paper, Na₂S₂O₃·5H₂O, a novel space holder, was used to prepare aluminium foam and copper foam, which were then used to test the heat dissipation performance of the metal foams. We first prepared two kinds of cell structures for (spherical cell and composite cells) aluminium and copper foam, then, we compared the performances of their heat dissipation, and it was found that both the spherical cell metal foam and composite cell metal foam promoted heat dissipation in the environment of natural convection, and the difference between them was not apparent. In the environment of forced convection, the composite porous metal showed a better heat dissipation performance. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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10 pages, 4178 KiB

Open AccessArticle

Improved Compressive Properties of Lattice Structure Based on an Implicit Surface Hybrid Optimization Design Method via Selective Laser Melting

by Xiong Xiao, Liangwen Xie, Rongyao Tang, Jiaan Liu, Peng Song, Xianyong Zhu, Jiali Zhao, Cheng Jiang, Song Yang and Peng Wu

Metals 2022, 12(9), 1477; https://doi.org/10.3390/met12091477 - 05 Sep 2022

Cited by 4 | Viewed by 1442

Abstract

In recent years, the lattice structure produced by additive manufacturing is a type of metal foam that has been increasingly investigated for its unique mechanical properties. However, the conventional Computer-Aided Design (CAD) is inefficient, the triply periodic minimal surfaces are rarely mixed, and [...] Read more.

In recent years, the lattice structure produced by additive manufacturing is a type of metal foam that has been increasingly investigated for its unique mechanical properties. However, the conventional Computer-Aided Design (CAD) is inefficient, the triply periodic minimal surfaces are rarely mixed, and the smooth transitions at the boundaries are not considered. In this study, a hybrid optimization design method based on implicit surfaces is proposed, which combines multiple implicit surfaces to achieve the continuous change in the curvature at the structure junctions and reduce the stress concentration. The hybrid lattice structures designed by this method were additively manufactured using 316L alloy via a selective laser melting. The results of the finite element analysis and mechanical compression test show that the hybrid lattice structures generated by this method exhibit a higher yield strength and energy absorption. These works can be used for other implicit surfaces, improve and enrich the types of implicit surfaces, and provide more good choices for practical applications. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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13 pages, 7062 KiB

Open AccessArticle

Quasi-Static Three-Point Bending Behavior of Aluminum Foam Sandwich with CFRP Face-Sheets

by Xinyuan Wang, Zhuokun Cao and Gaofeng Fu

Metals 2022, 12(8), 1393; https://doi.org/10.3390/met12081393 - 22 Aug 2022

Cited by 4 | Viewed by 1921

Abstract

Aluminum foam sandwich panels are excellent structure–function integrated materials. With high specific strength, cushioning energy absorption and sound absorption of aluminum foam material, they overcome the disadvantage of the low strength of single aluminum foam materials. In this paper, the response of aluminum [...] Read more.

Aluminum foam sandwich panels are excellent structure–function integrated materials. With high specific strength, cushioning energy absorption and sound absorption of aluminum foam material, they overcome the disadvantage of the low strength of single aluminum foam materials. In this paper, the response of aluminum sandwich panels comprising aluminum foam cores and carbon fiber reinforced plastic (CFRP) face-sheets was investigated under quasi-static three-point bending, and the effect of core thickness as well as core density on flexural loads and deformation modes was studied. The experimental results show that increasing the thickness and the density of the core materials can increase the flexural load and bending stiffness in the bending process. The aluminum foam sandwich panels mainly include the following deformation modes in the three-point bending process: indentation, core shear, face-sheet fracture and debonding. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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7 pages, 1559 KiB

Open AccessCommunication

Fabrication and Characterization of Porous Copper with Ultrahigh Porosity

by Jian Xiao, Yong Li, Jinming Liu and Qianlei Zhao

Metals 2022, 12(8), 1263; https://doi.org/10.3390/met12081263 - 27 Jul 2022

Cited by 5 | Viewed by 1755

Abstract

The fabrication of porous copper with ultrahigh porosity by adding 90% spacer content was an unsolved technical problem in the field. In this study, the green compacts placed on a layer wire mesh during the decomposition process of needlelike carbamide as space holder [...] Read more.

The fabrication of porous copper with ultrahigh porosity by adding 90% spacer content was an unsolved technical problem in the field. In this study, the green compacts placed on a layer wire mesh during the decomposition process of needlelike carbamide as space holder with volume content up to 90% was successfully conducted to fabricate nondestructive porous copper. Compared with the green compacts directly placed on an alumina plate, the use of this support was crucial for manufacturing highly-porous copper. Characterization of macro- and microscopic morphologies as well as quasi-static compressive test for the obtained porous copper samples was carried out. The results show that the porosity of porous copper samples with 87.3% was slightly smaller than the spacer content. The SEM observation indicates that the internal pores of porous copper formed an open-cell structure and its skeleton was very dense. The compressive tests show that the stress–strain curve of a porous copper sample exhibits the typical characteristics of elastic-plastic metal foam. The energy absorption properties of porous copper samples were also comparable. This study provides a possibility for the preparation of porous copper and other metals with ultrahigh porosity by the well-known space holder method. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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10 pages, 19150 KiB

Open AccessArticle

The Microstructure and the Properties of 304 and 430 Steel Foams Prepared by Powder Metallurgy Using CaCl₂ as a Space Holder

by Jichao Liang, Guangcheng Zhang, Yun Zhou, Shaowei Song, Xiaoqing Zuo and Hui Wang

Metals 2022, 12(7), 1182; https://doi.org/10.3390/met12071182 - 12 Jul 2022

Viewed by 1650

Abstract

In order to prepare stainless steel foams (SSFs) with high specific strength, cost-effective performance, and multiple relative density ranges, this work used CaCl₂ as a space holder to prepare 304 and 430 SSF samples with different relative densities using the powder metallurgy [...] Read more.

In order to prepare stainless steel foams (SSFs) with high specific strength, cost-effective performance, and multiple relative density ranges, this work used CaCl₂ as a space holder to prepare 304 and 430 SSF samples with different relative densities using the powder metallurgy method. The microstructure and the properties were compared and analyzed by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and a universal testing machine. The results show that the matrix of 304 SSFs is austenite and 430 is ferrite. In the quasi-static compression test, when the relative density was in the range of 0.33~0.12, their compressive strength increased with the relative density increasing; the maximum compressive strength of 304 SSFs reached 40.29 MPa and that of 430 SSFs was 49.79 MPa. While the compressive strength of 430 SSFs is significantly higher than 304 SSFs at a similar relative density, 304 SSFs show better stability in the plastic deformation stage. When the deformation reached densification, the maximum energy absorption value of 304 SSFs reached 15.94 MJ/m³, while 430 SSFs was 22.70 MJ/m³. The energy absorption value increased with the relative density increasing, and 430 SSFs exhibited a higher energy absorption capacity than 304 SSFs. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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8 pages, 1897 KiB

Open AccessCommunication

New Insights into Fabrication of Al-Based Foam with Homogeneous Small Pore-Structure Using MgCO₃/Zn Composite Powder as a Foaming Agent

by Xianzhen Wang, Qingxuan Meng, Tianze Wang, Xuming Chu, Aiqin Fan and Hui Wang

Metals 2022, 12(5), 786; https://doi.org/10.3390/met12050786 - 02 May 2022

Cited by 6 | Viewed by 1532

Abstract

Due to its excellent mechanical properties and ultra-lightweight, Al-based foam with homogeneous small pore-structures has wide applicational prospects in many industrial fields. However, during the foaming process of molten Al, it is difficult to manipulate the pore structures of the Al-based foam by [...] Read more.

Due to its excellent mechanical properties and ultra-lightweight, Al-based foam with homogeneous small pore-structures has wide applicational prospects in many industrial fields. However, during the foaming process of molten Al, it is difficult to manipulate the pore structures of the Al-based foam by means of the ALPORAS^© production route due to the violent gas-releasing performance of TiH₂ as a traditional foaming agent. Herein, we developed the melt-foaming route, that is, using MgCO₃/Zn composite powder as a foaming agent instead of TiH₂, the Al-based foam with homogeneous small pore-structures (average diameter was about 1 mm) was prepared successfully. Meanwhile, the decomposition model of the MgCO₃/Zn composite powder was proposed and further verified experimentally. The decomposition kinetics of the MgCO₃/Zn composite powder was also analyzed. Our findings not only shed light on the practical manufacturing of Al-based foam with homogeneous small pore-structures, but provide an insightful improvement for melt-foaming approaches. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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18 pages, 5989 KiB

Open AccessArticle

Low-Temperature Reactive Sintered Porous Mg-Al-Zn Alloy Foams

by Solomon-Oshioke Agbedor, Donghui Yang, Jianqing Chen, Lei Wang and Hong Wu

Metals 2022, 12(4), 692; https://doi.org/10.3390/met12040692 - 18 Apr 2022

Cited by 7 | Viewed by 1811

Abstract

By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn [...] Read more.

By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn (x = 1, 5) alloy foams was investigated. The phase diagram simulation approach was used to determine the sintering temperature. The analysis results show that the formation of binary secondary phases or intermetallic compounds is a crucial factor in achieving bonding strength for the porous Mg alloy foams. The intermetallic compounds were formed by solid-state diffusion between the metal powder elements. Mg₁₇Al₁₂ intermetallics was the most stable compound formed in the cell walls of porous Mg alloy foams. The addition of Zn influences the solubility and stability of the intermetallic compound. Thermodynamic calculations show that Mg₁₇Al₁₂ was preferentially formed in the cell walls owing to its high negative enthalpy energy. Moreover, various metastable transition phases may exist in the microstructures, especially in the porous Mg-9Al-5Zn alloy foam. The intermetallic phases act as reinforcing phases, combined with grain refinement, significantly increasing the strength of the foam. At the given relative density of 0.42, the porous Mg-9Al-5Zn alloy foam exhibits the highest yield strength of 9.0 MPa, which is 23% higher than the strength of the porous Mg-9Al-1Zn alloy foam. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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14 pages, 4209 KiB

Open AccessArticle

Tensile Behavior and Performance of Syntactic Steel Foams Prepared by Infiltration Casting

by Yong Mei, Chao Fu, Ying Fu, Yong Ding, Enge Wang and Quanzhan Yang

Metals 2022, 12(4), 668; https://doi.org/10.3390/met12040668 - 14 Apr 2022

Cited by 1 | Viewed by 1519

Abstract

Syntactic steel foams (SSFs) were prepared by low-pressure infiltration of molten ASTM CF-8 cast austenitic stainless steel into randomly and densely packed Al₂O₃ hollow spheres. The microstructure of the SSFs was characterized by scanning electron microscopy and energy dispersive spectrometry. [...] Read more.

Syntactic steel foams (SSFs) were prepared by low-pressure infiltration of molten ASTM CF-8 cast austenitic stainless steel into randomly and densely packed Al₂O₃ hollow spheres. The microstructure of the SSFs was characterized by scanning electron microscopy and energy dispersive spectrometry. Using dumbbell-shaped specimens, the density of the as-cast SSFs is measured in the range from 3.33 to 3.64 g/cm³ and their ultimate tensile strength from 83.1 to 97.6 MPa. No significant chemical reaction was detected between the fillers and matrix. The quasi-static uniaxial tensile deformation of the syntactic foams underwent elastic deformation, plastic deformation, and then a failure stage, showing similar tensile behavior to plastic bulk metals but different behavior to common metal foams. From the good ductility of the metal matrix, a clear macroscopic plastic deformation was observed before the ductile fracture of the syntactic foams. A constitutive relationship of the SSFs under uniaxial tensile loads has been proposed. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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7 pages, 24191 KiB

Open AccessCommunication

Generation of a Strength Gradient in Al-Cu-Ca Alloy Foam via Graded Aging Treatment

by Wei Zhao, Siyuan He, Chen Zhang, Yuxuan Li, Yi Zhang and Ge Dai

Metals 2022, 12(3), 423; https://doi.org/10.3390/met12030423 - 28 Feb 2022

Cited by 2 | Viewed by 1561

Abstract

In this study, a strength gradient is produced in Al-Cu-Ca alloy foam by aging treatment with a temperature gradient. The microscopic results show that the morphology and the amount of Al₂Cu strengthening precipitates in the base alloy change with the local [...] Read more.

In this study, a strength gradient is produced in Al-Cu-Ca alloy foam by aging treatment with a temperature gradient. The microscopic results show that the morphology and the amount of Al₂Cu strengthening precipitates in the base alloy change with the local aging temperature. Graded microstructures in the base alloy are realized along with the temperature gradient, subsequently producing the strength gradient in the Al-Cu-Ca foam. Under compression, the lower strength portion of the foam sample firstly collapsed until complete densification and then extended to the higher strength portion, suggesting a notable strength gradient. The tailorable graded aging treatment provided a higher degree of freedom in designing and producing the strength gradient in aluminum foam. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)

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