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Metals, Volume 2, Issue 1 (March 2012) – 6 articles , Pages 1-78

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Research

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3258 KiB  
Article
Method of Preventing Shrinkage of Aluminum Foam Using Carbonates
by Takuya Koizumi, Kota Kido, Kazuhiko Kita, Koichi Mikado, Svyatoslav Gnyloskurenko and Takashi Nakamura
Metals 2012, 2(1), 1-9; https://doi.org/10.3390/met2010001 - 23 Dec 2011
Cited by 14 | Viewed by 7046
Abstract
Metallic foams are commonly produced using titanium hydride as a foaming agent. Carbonates produce aluminum foam with a fine and homogenous cell structure. However, foams produced using carbonates show marked shrinkage, which is clearly different from those produced using titanium hydride. It is [...] Read more.
Metallic foams are commonly produced using titanium hydride as a foaming agent. Carbonates produce aluminum foam with a fine and homogenous cell structure. However, foams produced using carbonates show marked shrinkage, which is clearly different from those produced using titanium hydride. It is essential for practical applications to clarify foam shrinkage and establish a method of preventing it. In this research, cell structures were observed to study the shrinkage of aluminum foam produced using carbonates. The cells of foam produced using dolomite as a foaming agent connected to each other with maximum expansion. It was estimated that foaming gas was released through connected cells to the outside. It was assumed that cell formation at different sites is effective in preventing shrinkage induced by cell connection. The multiple additions of dolomite and magnesium carbonate, which have different decomposition temperatures, were applied. The foam in the case with multiple additions maintained a density of 0.66 up to 973 K, at which the foam produced using dolomite shrank. It was verified that the multiple additions of carbonates are effective in preventing shrinkage. Full article
(This article belongs to the Special Issue Metal Foams)
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708 KiB  
Article
Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading
by Andreas Böhner, Thomas Niendorf, Doris Amberger, Heinz Werner Höppel, Mathias Göken and Hans Jürgen Maier
Metals 2012, 2(1), 56-64; https://doi.org/10.3390/met2010056 - 02 Feb 2012
Cited by 13 | Viewed by 7911
Abstract
The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar [...] Read more.
The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition. Full article
(This article belongs to the Special Issue Processing and Properties of Bulk Nanostructured Materials)
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2493 KiB  
Article
Crack Propagation in Honeycomb Cellular Materials: A Computational Approach
by Marco Paggi
Metals 2012, 2(1), 65-78; https://doi.org/10.3390/met2010065 - 13 Feb 2012
Cited by 12 | Viewed by 6748
Abstract
Computational models based on the finite element method and linear or nonlinear fracture mechanics are herein proposed to study the mechanical response of functionally designed cellular components. It is demonstrated that, via a suitable tailoring of the properties of interfaces present in the [...] Read more.
Computational models based on the finite element method and linear or nonlinear fracture mechanics are herein proposed to study the mechanical response of functionally designed cellular components. It is demonstrated that, via a suitable tailoring of the properties of interfaces present in the meso- and micro-structures, the tensile strength can be substantially increased as compared to that of a standard polycrystalline material. Moreover, numerical examples regarding the structural response of these components when subjected to loading conditions typical of cutting operations are provided. As a general trend, the occurrence of tortuous crack paths is highly favorable: stable crack propagation can be achieved in case of critical crack growth, whereas an increased fatigue life can be obtained for a sub-critical crack propagation. Full article
(This article belongs to the Special Issue Nanocrystalline Metals and Alloys)
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Review

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1546 KiB  
Review
Metal Foaming Investigated by X-ray Radioscopy
by Francisco Garcia-Moreno, Manas Mukherjee, Catalina Jiménez, Alexander Rack and John Banhart
Metals 2012, 2(1), 10-21; https://doi.org/10.3390/met2010010 - 27 Dec 2011
Cited by 38 | Viewed by 9986
Abstract
The use of X-ray radioscopy for in-situ studies of metal foam formation and evolution is reviewed. Selected results demonstrate the power of X-ray radioscopy as diagnostic tool for metal foaming. Qualitative analyses of foam nucleation and evolution, drainage development, issues of thermal contact, [...] Read more.
The use of X-ray radioscopy for in-situ studies of metal foam formation and evolution is reviewed. Selected results demonstrate the power of X-ray radioscopy as diagnostic tool for metal foaming. Qualitative analyses of foam nucleation and evolution, drainage development, issues of thermal contact, mold filling, cell wall rupture and more are given. Additionally, quantitative analyses based on series of images of foam expansion yielding coalescence rates, density distributions, etc., are performed by dedicated software. These techniques help us to understand the foaming behavior of metals and to improve both foaming methods and foam quality. Full article
(This article belongs to the Special Issue Metal Foams)
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2280 KiB  
Review
Nanocrystalline Metal Hydrides Obtained by Severe Plastic Deformations
by Jacques Huot
Metals 2012, 2(1), 22-40; https://doi.org/10.3390/met2010022 - 10 Jan 2012
Cited by 38 | Viewed by 7539
Abstract
It has recently been shown that Severe Plastic Deformation (SPD) techniques could be used to obtain nanostructured metal hydrides with enhanced hydrogen sorption properties. In this paper we review the different SPD techniques used on metal hydrides and present some specific cases of [...] Read more.
It has recently been shown that Severe Plastic Deformation (SPD) techniques could be used to obtain nanostructured metal hydrides with enhanced hydrogen sorption properties. In this paper we review the different SPD techniques used on metal hydrides and present some specific cases of the effect of cold rolling on the hydrogen storage properties and crystal structure of various types of metal hydrides such as magnesium-based alloys and body centered cubic (BCC) alloys. Results show that generally cold rolling is as effective as ball milling to enhance hydrogen sorption kinetics. However, for some alloys such as TiV0.9Mn1.1 alloy ball milling and cold rolling have detrimental effect on hydrogen capacity. The exact mechanism responsible for the change in hydrogenation properties may not be the same for ball milling and cold rolling. Nevertheless, particle size reduction and texture seems to play a leading role in the hydrogen sorption enhancement of cold rolled metal hydrides. Full article
(This article belongs to the Special Issue Nanocrystalline Metals and Alloys)
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321 KiB  
Review
The Cyclic Deformation Behavior of Severe Plastic Deformation (SPD) Metals and the Influential Factors
by Charles C. F. Kwan and Zhirui Wang
Metals 2012, 2(1), 41-55; https://doi.org/10.3390/met2010041 - 01 Feb 2012
Cited by 11 | Viewed by 7194
Abstract
A deeper understanding of the mechanical behavior of ultra-fine (UF) and nanocrystalline (NC) grained metals is necessary with the growing interest in using UF and NC grained metals for structural applications. The cyclic deformation response and behavior of UF and NC grained metals [...] Read more.
A deeper understanding of the mechanical behavior of ultra-fine (UF) and nanocrystalline (NC) grained metals is necessary with the growing interest in using UF and NC grained metals for structural applications. The cyclic deformation response and behavior of UF and NC grained metals is one aspect that has been gaining momentum as a major research topic for the past ten years. Severe Plastic Deformation (SPD) materials are often in the spotlight for cyclic deformation studies as they are usually in the form of bulk work pieces and have UF and NC grains. Some well known techniques in the category of SPD processing are High Pressure Torsion (HPT), Equal Channel Angular Pressing (ECAP), and Accumulative Roll-Bonding (ARB). In this report, the literature on the cyclic deformation response and behavior of SPDed metals will be reviewed. The cyclic response of such materials is found to range from cyclic hardening to cyclic softening depending on various factors. Specifically, for SPDed UF grained metals, their behavior has often been associated with the observation of grain coarsening during cycling. Consequently, the many factors that affect the cyclic deformation response of SPDed metals can be summarized into three major aspects: (1) the microstructure stability; (2) the limitation of the cyclic lifespan; and lastly (3) the imposed plastic strain amplitude. Full article
(This article belongs to the Special Issue Processing and Properties of Bulk Nanostructured Materials)
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