http://www.mdpi.com/journal/metals Latest open access articles published in Metals at http://www.mdpi.com/journal/metals http://www.mdpi.com/2075-4701/2/2/95 The results of the present study highlight the role of foaming agent and processing route in influencing the contamination of cell wall material by side products, which, in turn, affect the macroscopic mechanical response of closed-cell Al-foams. Several kinds of Al-foams have been produced with pure Al by the Alporas melt process and powder metallurgical technique, all performed either with conventional TiH2 foaming agent or CaCO3 as an alternative. Mechanical characteristics of contaminating products induced by processing additives, all of which were presented in one or another kind of Al-foam, have been determined in indentation experiments. Damage behavior of these contaminations affects the micro-mechanism of deformation and favors either plastic buckling or brittle failure of the cell walls. It is justified that there is no discrepancy between experimental values of compressive strengths for Al-foams comprising ductile Al + Al4Ca eutectic domains and those prescribed by theoretical models for closed-cell structure. However, the presence of low ductile Al + Al3Ti + Al4Ca eutectic domains and brittle particles/layers of Al3Ti, fine CaCO3/CaO particles, Al2O3 oxide network, and, especially, residues of partially reacted TiH2, results in reducing the compressive strength to values close to or even below those of open-cell foams of the same relative density. http://www.mdpi.com/2075-4701/2/2/95 Wed, 23 May 2012 00:00:00 CEST Metals 2012-05-23 2 2 Article 95 112 2075-4701 The Role of Foaming Agent and Processing Route in the Mechanical Performance of Fabricated Aluminum Foams 2012-05-23 doi: 10.3390/met2020095 Alexandra Byakova Svyatoslav Gnyloskurenko Takashi Nakamura http://www.mdpi.com/2075-4701/2/2/79 Brass-matrix composites reinforced with 40 and 60 vol.% of Ni59Zr20Ti16Si2Sn3 glassy particles were produced by powder metallurgy. The crystallization behavior and the temperature dependence of the viscosity of the glass reinforcement were studied in detail to select the proper sintering parameters in order to avoid crystallization of the glassy phase during consolidation. The brass-glass powder mixtures were prepared through manual blending as well as by ball milling to analyze the effect of the matrix ligament size on the mechanical properties of the composites. The powder mixtures were then consolidated into highly-dense bulk specimens at temperatures within the supercooled liquid region by hot pressing followed by hot extrusion. The preparation of the powder mixtures has a strong influence on the mechanical behavior of the composites. The strength increases from 500 MPa for pure brass to 740 and 925 MPa for the blended composites with 40 and 60vol.% of glass reinforcement, while the strength increases to 1,240 and 1,640 MPa for the corresponding composites produced by ball milling. Modeling of the mechanical properties indicates that this behavior is related to the reduced matrix ligament size characterizing the milled composites. http://www.mdpi.com/2075-4701/2/2/79 Tue, 15 May 2012 00:00:00 CEST Metals 2012-05-15 2 2 Article 79 94 2075-4701 Production and Characterization of Brass-matrix Composites Reinforced with Ni59Zr20Ti16Si2Sn3 Glassy Particles 2012-05-15 doi: 10.3390/met2020079 Jin Young Kim Sergio Scudino Uta Kühn Bum Sung Kim Min Ha Lee Jürgen Eckert http://www.mdpi.com/2075-4701/2/1/65 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. http://www.mdpi.com/2075-4701/2/1/65 Mon, 13 Feb 2012 00:00:00 CET Metals 2012-02-13 2 1 Article 65 78 2075-4701 Crack Propagation in Honeycomb Cellular Materials: A Computational Approach 2012-02-13 doi: 10.3390/met2010065 Marco Paggi http://www.mdpi.com/2075-4701/2/1/56 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. http://www.mdpi.com/2075-4701/2/1/56 Thu, 02 Feb 2012 00:00:00 CET Metals 2012-02-02 2 1 Article 56 64 2075-4701 Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading 2012-02-02 doi: 10.3390/met2010056 Andreas Böhner Thomas Niendorf Doris Amberger Heinz Werner Höppel Mathias Göken Hans Jürgen Maier http://www.mdpi.com/2075-4701/2/1/41 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. http://www.mdpi.com/2075-4701/2/1/41 Wed, 01 Feb 2012 00:00:00 CET Metals 2012-02-01 2 1 Review 41 55 2075-4701 The Cyclic Deformation Behavior of Severe Plastic Deformation (SPD) Metals and the Influential Factors 2012-02-01 doi: 10.3390/met2010041 Charles C. F. Kwan Zhirui Wang http://www.mdpi.com/2075-4701/2/1/22 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. http://www.mdpi.com/2075-4701/2/1/22 Tue, 10 Jan 2012 00:00:00 CET Metals 2012-01-10 2 1 Review 22 40 2075-4701 Nanocrystalline Metal Hydrides Obtained by Severe Plastic Deformations 2012-01-10 doi: 10.3390/met2010022 Jacques Huot http://www.mdpi.com/2075-4701/2/1/10 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. http://www.mdpi.com/2075-4701/2/1/10 Tue, 27 Dec 2011 00:00:00 CET Metals 2011-12-27 2 1 Review 10 21 2075-4701 Metal Foaming Investigated by X-ray Radioscopy 2011-12-27 doi: 10.3390/met2010010 Francisco Garcia-Moreno Manas Mukherjee Catalina Jiménez Alexander Rack John Banhart http://www.mdpi.com/2075-4701/2/1/1 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. http://www.mdpi.com/2075-4701/2/1/1 Fri, 23 Dec 2011 00:00:00 CET Metals 2011-12-23 2 1 Article 1 9 2075-4701 Method of Preventing Shrinkage of Aluminum Foam Using Carbonates 2011-12-23 doi: 10.3390/met2010001 Takuya Koizumi Kota Kido Kazuhiko Kita Koichi Mikado Svyatoslav Gnyloskurenko Takashi Nakamura http://www.mdpi.com/2075-4701/1/1/98 The structures realized using sandwich technologies combine low weight with high energy absorbing capacity, so they are suitable for applications in the transport industry (automotive, aerospace, shipbuilding industry) where the “lightweight design” philosophy and the safety of vehicles are very important aspects. While sandwich structures with polymeric foams have been applied for many years, currently there is a considerable and growing interest in the use of sandwiches with aluminum foam core. The aim of this paper was the analysis of low-velocity impact response of AFS (aluminum foam sandwiches) panels and the investigation of their collapse modes. Low velocity impact tests were carried out by a drop test machine and a theoretical approach, based on the energy balance model, has been applied to investigate their impact behavior. The failure mode and the internal damage of the impacted AFS have also been investigated by a Computed Tomography (CT) system. http://www.mdpi.com/2075-4701/1/1/98 Thu, 15 Dec 2011 00:00:00 CET Metals 2011-12-15 1 1 Article 98 112 2075-4701 Impact Response of Aluminum Foam Sandwiches for Light-Weight Ship Structures 2011-12-15 doi: 10.3390/met1010098 Vincenzo Crupi Gabriella Epasto Eugenio Guglielmino http://www.mdpi.com/2075-4701/1/1/79 An alternative deformation technique was applied to a composite made of titanium and an aluminium alloy in order to achieve severe plastic deformation. This involves accumulative swaging and bundling. Furthermore, it allows uniform deformation of a composite material while producing a wire which can be further used easily. Detailed analysis concerning the control of the deformation process, mesostructural and microstructural features and tensile testing was carried out on the as produced wires. A strong grain refinement to a grain size of 250–500 nm accompanied by a decrease in 〈111〉 fibre texture component and a change from low angle to high angle grain boundary characteristics is observed in the Al alloy. A strong increase in the mechanical properties in terms of ultimate tensile strength ranging from 600 to 930 MPa being equivalent to a specific strength of up to 223 MPa/g/cm3 was achieved. http://www.mdpi.com/2075-4701/1/1/79 Thu, 17 Nov 2011 00:00:00 CET Metals 2011-11-17 1 1 Article 79 97 2075-4701 Ti-Al Composite Wires with High Specific Strength 2011-11-17 doi: 10.3390/met1010079 Tom Marr Jens Freudenberger Dirk Seifert Hansjörg Klauß Jan Romberg Ilya Okulov Juliane Scharnweber Andy Eschke Carl-Georg Oertel Werner Skrotzki Uta Kühn Jürgen Eckert Ludwig Schultz http://www.mdpi.com/2075-4701/1/1/65 The formation of alloys by particle reinforcement during accumulative roll bonding (ARB), and subsequent annealing, is introduced on the basis of the binary alloy system Al-Cu, where strength and electrical conductivity are examined in different microstructural states. An ultimate tensile strength (UTS) of 430 MPa for Al with 1.4 vol.% Cu was reached after three ARB cycles, which almost equals UTS of the commercially available Al-Cu alloy AA2017A with a similar copper content. Regarding electrical conductivity, the UFG structure had no significant influence. Alloying of aluminum with copper leads to a linear decrease in conductivity of 0.78 µΩ∙cm/at.% following the Nordheim rule. On the copper-rich side, alloying with aluminum leads to a slight strengthening, but drastically reduces conductivity. A linear decrease of electrical conductivity of 1.19 µΩ∙cm/at.% was obtained. http://www.mdpi.com/2075-4701/1/1/65 Mon, 07 Nov 2011 00:00:00 CET Metals 2011-11-07 1 1 Article 65 78 2075-4701 Particle Based Alloying by Accumulative Roll Bonding in the System Al-Cu 2011-11-07 doi: 10.3390/met1010065 Christian W. Schmidt Patrick Knödler Heinz Werner Höppel Mathias Göken http://www.mdpi.com/2075-4701/1/1/49 Open cell Al foams have been made by infiltrating molten Al into preforms made from porous salt spheres. Infiltration has been effected using simple pressure-assisted vacuum investment casting where the maximum infiltration pressure difference was less than 36 psi. The preform and resulting foam density decreased with increasing compaction pressure and the foam density increased with increasing infiltration pressure. For low pressure infiltration, and high density preforms, salt dissolution was rapid due to the porous nature of the salt spheres. Infiltration of molten Al occurred into the beads and, for high density preforms and higher infiltration pressures, the volume of metal in the beads exceeded that in the cell walls, drastically decreasing the NaCl dissolution rate. A simple approach is shown whereby the data from mercury porosimetry can be used to predict the resulting foam density, thereby aiding the design of preform and beads structures. http://www.mdpi.com/2075-4701/1/1/49 Fri, 04 Nov 2011 00:00:00 CET Metals 2011-11-04 1 1 Article 49 64 2075-4701 The Manufacture and Characterisation of Aluminium Foams Made by Investment Casting Using Dissolvable Spherical Sodium Chloride Bead Preforms 2011-11-04 doi: 10.3390/met1010049 Apichart Jinnapat Andrew Kennedy http://www.mdpi.com/2075-4701/1/1/16 Control of the material microstructure in terms of the grain size is a key component in tailoring material properties of metals and alloys and in creating functionally graded materials. To exert this control, reliable and efficient modeling and simulation of the recrystallization process whereby the grain size evolves is vital. The present contribution is a review paper, summarizing the current status of various approaches to modeling grain refinement due to recrystallization. The underlying mechanisms of recrystallization are briefly recollected and different simulation methods are discussed. Analytical and empirical models, continuum mechanical models and discrete methods as well as phase field, vertex and level set models of recrystallization will be considered. Such numerical methods have been reviewed previously, but with the present focus on recrystallization modeling and with a rapidly increasing amount of related publications, an updated review is called for. Advantages and disadvantages of the different methods are discussed in terms of applicability, underlying assumptions, physical relevance, implementation issues and computational efficiency. http://www.mdpi.com/2075-4701/1/1/16 Fri, 28 Oct 2011 00:00:00 CEST Metals 2011-10-28 1 1 Review 16 48 2075-4701 Approaches to Modeling of Recrystallization 2011-10-28 doi: 10.3390/met1010016 Håkan Hallberg http://www.mdpi.com/2075-4701/1/1/3 Nanocrystalline Al–Mg dendrites were fabricated through galvanostatic electrodeposition. Initially feather-like morphology was formed exhibiting morphological evolution to smooth globules at its tips. With eventual deposition, rough globules formed over the smooth ones. The feather-like and smooth globules possessed supersaturated face centered cubic (fcc)–Al(Mg) phase with ~7 and ~20 at.% Mg respectively. The rough globules contained hexagonal close packed (hcp)–Mg(Al) phase with ~80 at.% Mg. Microstructural examinations revealed that the feather-like and rough globules possessed grain sizes of ~42 ± 15 and ~36 ± 12 nm respectively. The region, which exhibited morphological evolution from feather-like to smooth globules, possessed ~16 ± 7 nm grain size. The observed microstructural and compositional features were attributed to the local current density values. The formation of the Al–Mg dendrites is discussed in this paper. http://www.mdpi.com/2075-4701/1/1/3 Mon, 05 Sep 2011 00:00:00 CEST Metals 2011-09-05 1 1 Article 3 15 2075-4701 Evolution of Morphology and Microstructure in Electrodeposited Nanocrystalline Al–Mg Alloy Dendrites 2011-09-05 doi: 10.3390/met1010003 Sankara Sarma V. Tatiparti Fereshteh Ebrahimi http://www.mdpi.com/2075-4701/1/1/1 As I assume the role of Editor-in-Chief of this new journal, I look forward to serving in contributing to the advance of science and engineering in the field of metallic materials. This formidable task is made possible thanks to the excellent support of the Publisher and of the Editorial Staff of MDPI, as well as to a highly qualified Editorial Board. Hence, it is with pleasure that I accept this challenge, and I look forward to work with all of you in expanding the field of metals through journal contributions of current importance and of great interest to the scientific community. [...] http://www.mdpi.com/2075-4701/1/1/1 Fri, 25 Feb 2011 00:00:00 CET Metals 2011-02-25 1 1 Editorial 1 2 2075-4701 Welcome to Metals––a New Open Access Journal for a Growing Scientific Community 2011-02-25 doi: 10.3390/met1010001 Hugo F. López