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Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports...
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Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692

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

Deadline for manuscript submissions: closed (15 December 2017) | Viewed by 76401

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

Special Issue Editor

Prof. Dr. Martin F.-X. Wagner

E-Mail Website
Guest Editor
Institute of Materials Science and Engineering, Chair of Materials Science, TU Chemnitz, Germany; Collaborative Research Center 692 – High-strength aluminum-based light-weight materials for safety components, TU Chemnitz, Germany
Interests: mechanical behavior of structural and functional materials on all length scales; experimental and theoretical aspects of twinning; light metals; severe plastic deformation; ultrafine-grained microstructures; ultra-high strength steels; high strain rate testing

Special Issue Information

Dear Colleagues,

Academia and industry alike are faced with an ever-growing demand for energy-efficiency and reduced weights. Aluminum-based light-weight materials offer great potential for novel engineering applications, particularly when they are optimized to exhibit high strength and yet provide sufficient reliability. The last decade has thus seen substantial activity in the research fields of high-strength aluminum alloys and aluminum-based composite materials. For twelve years, backed by solid funding of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG), scientists of the Collaborative Research Center; High-strength aluminum-based light-weight materials for safety components (SFB 692) at TU Chemnitz, Germany, have contributed to this research area. Our research efforts have been focused on three main areas: ultrafine-grained aluminum alloys produced by severe plastic deformation; aluminum matrix composites; and aluminum-based composite materials (including material combinations like magnesium/aluminum or steel/aluminum and the corresponding joining and forming technologies). The framework of SFB 692 has served as a common basis for numerous scientific collaborations between scientists from the fields of materials science, design engineering, forming technology, production engineering, mechanics, and even economics in Chemnitz, and with many well-established international experts around the world. In this Special Issue of the well-established Metals journal, we intend to present recent results on high-strength aluminum-based light-weight materials that also provide a broad overview of the research activities in SFB 692 and beyond. While the Special Issue is primarily focused on work from the Research Center, we also welcome submissions from our collaborators and other experts in the field.

Prof. Dr. Martin F.-X. Wagner
Guest Editor

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

  • Light-weight materials
  • Aluminum alloys
  • Aluminum matrix composites
  • Aluminum-magnesium composites
  • Interfaces
  • Severe plastic deformation
  • Ultrafine-grained materials
  • Equal-channel angular pressing
  • Thermal stability
  • Creep
  • Precipitation
  • Forming technology
  • Materials science
  • Surface engineering
  • Mechanics and modeling

Published Papers (16 papers)

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Editorial

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4 pages, 202 KiB  
Editorial
Light-Weight Aluminum-Based Alloys—From Fundamental Science to Engineering Applications
by Martin Franz-Xaver Wagner
Metals 2018, 8(4), 260; https://doi.org/10.3390/met8040260 - 11 Apr 2018
Cited by 10 | Viewed by 3331
Abstract
Academia and industry alike are faced with an ever-growing demand for energy-efficiency and reduced mass [...]
Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)

Research

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12 pages, 28008 KiB  
Article
Arc Brazing of Aluminium, Aluminium Matrix Composites and Stainless Steel in Dissimilar Joints
by Thomas Grund, Andreas Gester, Guntram Wagner, Stefan Habisch and Peter Mayr
Metals 2018, 8(3), 166; https://doi.org/10.3390/met8030166 - 08 Mar 2018
Cited by 6 | Viewed by 4360
Abstract
The publication describes the approaches and results of the investigation of arc brazing processes to produce dissimilar joints of particle reinforced aluminium matrix composites (AMC) to aluminium alloys and steels. Arc brazing allows for low thermal energy input to the joint parts, and [...] Read more.
The publication describes the approaches and results of the investigation of arc brazing processes to produce dissimilar joints of particle reinforced aluminium matrix composites (AMC) to aluminium alloys and steels. Arc brazing allows for low thermal energy input to the joint parts, and is hence suitable to be applied to AMC. In addition, a braze filler B-Al40Ag40Cu20 alloyed with Si with a liquidus temperature of below 500 °C is selected to further reduce the thermal energy input during joining. The microstructures of the joining zones were analysed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and X-ray diffraction analysis (XRD), as well as their hardness profile characterised and discussed. Joint strengths were measured by tensile shear tests, and resulting areas of fracture were discussed in accordance to the joints’ microstructures and gained bond strength values. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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14 pages, 3984 KiB  
Article
A Fragmentation Criterion for the Interface of a Hydrostatic Extruded Al-Mg-Compound
by Carola Kirbach, Martin Stockmann and Jörn Ihlemann
Metals 2018, 8(3), 157; https://doi.org/10.3390/met8030157 - 02 Mar 2018
Cited by 4 | Viewed by 3652
Abstract
Due to the higher demand for energy efficient products, light-weight constructions have become more important in recent years. An innovative, hydrostatic extruded Al-Mg-compound used here combines the corrosion resistance of aluminium with the outstanding lightweight properties of magnesium. During the production process, a [...] Read more.
Due to the higher demand for energy efficient products, light-weight constructions have become more important in recent years. An innovative, hydrostatic extruded Al-Mg-compound used here combines the corrosion resistance of aluminium with the outstanding lightweight properties of magnesium. During the production process, a thin boundary layer is built between the two basic materials. Investigations on further hot forming processing revealed a good formability of these compounds despite the fact that the boundary layer splits into fragments during forging and a new secondary boundary layer is built when the basic materials between the fragments come into contact again during the continuous deformation. The aim of the research is now to investigate fragmentation depending on the deformation rate and boundary layer thickness, which increases during the heat-up process in preparation of forging. For this purpose, a channel compression test is used in conjunction with a special newly developed specimen shape. The metallographic evaluation of the boundary layer reveals a strong dependency of fragmentation on the deformation rate and the boundary layer thickness. With the aid of a numerical simulation, an individual critical stretch could be determined at which fragmentation starts, and provide guidance for an optimal forging process design. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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11 pages, 956 KiB  
Article
Particle-Reinforced Aluminum Matrix Composites (AMCs)—Selected Results of an Integrated Technology, User, and Market Analysis and Forecast
by Anja Schmidt, Steve Siebeck, Uwe Götze, Guntram Wagner and Daisy Nestler
Metals 2018, 8(2), 143; https://doi.org/10.3390/met8020143 - 22 Feb 2018
Cited by 36 | Viewed by 4767
Abstract
The research and development of new materials such as particle-reinforced aluminum matrix composites (AMCs) will only result in a successful innovation if these materials show significant advantages not only from a technological, but also from an economic point of view. Against this background, [...] Read more.
The research and development of new materials such as particle-reinforced aluminum matrix composites (AMCs) will only result in a successful innovation if these materials show significant advantages not only from a technological, but also from an economic point of view. Against this background, in the Collaborative Research Center SFB 692, the concept of an integrated technology, user, and market analysis and forecast has been developed as a means for assessing the technological and commercial potential of new materials in early life cycle stages. After briefly describing this concept, it is applied to AMCs and the potential field of manufacturing aircraft components. Results show not only technological advances, but also considerable economic potential—the latter one primarily resulting from the possible weight reduction being enabled by the increased yield strength of the new material. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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15 pages, 4327 KiB  
Article
Effect of Nitric and Oxalic Acid Addition on Hard Anodizing of AlCu4Mg1 in Sulphuric Acid
by Maximilian Sieber, Roy Morgenstern, Ingolf Scharf and Thomas Lampke
Metals 2018, 8(2), 139; https://doi.org/10.3390/met8020139 - 17 Feb 2018
Cited by 11 | Viewed by 4807
Abstract
The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the [...] Read more.
The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the oxide coatings are significantly reduced in comparison to unalloyed substrates. With regard to this challenge, recent investigations have indicated a beneficial effect of nitric acid addition to the commonly used sulphuric acid electrolytes both in terms of coating properties and process efficiency. The present work investigates the anodic oxidation of the AlCu4Mg1 alloy in a sulphuric acid electrolyte with additions of nitric acid as well as oxalic acid as a reference in a full-factorial design of experiments (DOE). The effect of the electrolyte composition on process efficiency, coating thickness and hardness is established by using response functions. A mechanism for the participation of the nitric acid additive during the oxide formation is proposed. The statistical significance of the results is assessed by an analysis of variance (ANOVA). Eventually, scratch testing is applied in order to evaluate the failure mechanisms and the abrasion resistance of the obtained conversion coatings. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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12 pages, 8053 KiB  
Article
The Effect of Interlayer Materials on the Joint Properties of Diffusion-Bonded Aluminium and Magnesium
by Stefan Habisch, Marcus Böhme, Siegfried Peter, Thomas Grund and Peter Mayr
Metals 2018, 8(2), 138; https://doi.org/10.3390/met8020138 - 17 Feb 2018
Cited by 15 | Viewed by 6918
Abstract
Diffusion bonding is a well-known technology for a wide range of advanced joining applications, due to the possibility of bonding different materials within a defined temperature-time-contact pressure regime in solid state. For this study, aluminium alloys AA 6060, AA 6082, AA 7020, AA [...] Read more.
Diffusion bonding is a well-known technology for a wide range of advanced joining applications, due to the possibility of bonding different materials within a defined temperature-time-contact pressure regime in solid state. For this study, aluminium alloys AA 6060, AA 6082, AA 7020, AA 7075 and magnesium alloy AZ 31 B are used to produce dissimilar metal joints. Titanium and silver were investigated as interlayer materials. SEM and EDXS-analysis, micro-hardness measurements and tensile testing were carried out to examine the influence of the interlayers on the diffusion zone microstructures and to characterize the joint properties. The results showed that the highest joint strength of 48 N/mm2 was reached using an aluminium alloy of the 6000 series with a titanium interlayer. For both interlayer materials, intermetallic Al-Mg compounds were still formed, but the width and the level of hardness across the diffusion zone was significantly reduced compared to Al-Mg joints without interlayer. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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12 pages, 6074 KiB  
Article
Finite Element Simulation of the Presta Joining Process for Assembled Camshafts: Application to Aluminum Shafts
by Robert Scherzer, Sebastian Fritsch, Ralf Landgraf, Jörn Ihlemann and Martin Franz-Xaver Wagner
Metals 2018, 8(2), 128; https://doi.org/10.3390/met8020128 - 11 Feb 2018
Cited by 6 | Viewed by 4316
Abstract
This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the [...] Read more.
This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the joining of the cam onto the shaft. When manufactured, the connection is tested randomly by loading it with a static torque. Subsequently, there are three numerical models using the finite element method. Additionally, a material model of finite strain viscoplasticity with nonlinear kinematic hardening is used throughout the whole simulation process, which allows a realistic representation of the material behavior even for large deformations. In addition, it enables a transfer of the deformation history and of the internal stresses between different submodels. This work also shows the required parameter identification and the associated material tests. After comparing the numerical results with experimental studies of the manufacturing process for steel-steel connections, the models are used to extend the joining process to the utilization of aluminum shafts. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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10 pages, 5482 KiB  
Article
Influence of Boron on the Creep Behavior and the Microstructure of Particle Reinforced Aluminum Matrix Composites
by Steve Siebeck, Kristina Roder, Guntram Wagner and Daisy Nestler
Metals 2018, 8(2), 110; https://doi.org/10.3390/met8020110 - 06 Feb 2018
Cited by 4 | Viewed by 3877
Abstract
The reinforcement of aluminum alloys with particles leads to the enhancement of their mechanical properties at room temperature. However, the creep behavior at elevated temperatures is often negatively influenced. This raises the question of how it is possible to influence the creep behavior [...] Read more.
The reinforcement of aluminum alloys with particles leads to the enhancement of their mechanical properties at room temperature. However, the creep behavior at elevated temperatures is often negatively influenced. This raises the question of how it is possible to influence the creep behavior of this type of material. Within this paper, selected creep and tensile tests demonstrate the beneficial effects of boron on the properties of precipitation-hardenable aluminum matrix composites (AMCs). The focus is on the underlying microstructure behind this effect. For this purpose, boron was added to AMCs by means of mechanical alloying. Comparatively higher boron contents than in steel are investigated in order to be able to record their influence on the microstructure including the formation of potential new phases as well as possible. While the newly formed phase Al3BC can be reliably detected by X-ray diffraction (XRD), it is difficult to obtain information about the phase distribution by means of scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) investigations. An important contribution to this is finally provided by the investigation using Raman microscopy. Thus, the homogeneous distribution of finely scaled Al3BC particles is detectable, which allows conclusions about the microstructure/property relationship. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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11 pages, 3231 KiB  
Article
Process Chain for the Production of a Bimetal Component from Mg with a Complete Al Cladding
by Wolfgang Förster, Carolin Binotsch and Birgit Awiszus
Metals 2018, 8(2), 97; https://doi.org/10.3390/met8020097 - 27 Jan 2018
Cited by 12 | Viewed by 3646
Abstract
With respect to its density, magnesium (Mg) has a high potential for lightweight components. Nevertheless, the industrial application of Mg is limited due to, for example, its sensitivity to corrosion. To increase the applicability of Mg, a process chain for the production of [...] Read more.
With respect to its density, magnesium (Mg) has a high potential for lightweight components. Nevertheless, the industrial application of Mg is limited due to, for example, its sensitivity to corrosion. To increase the applicability of Mg, a process chain for the production of a Mg component with a complete aluminum (Al) cladding is presented. Hydrostatic co-extrusion was used to produce bar-shaped rods with a diameter of 20 mm. The bonding between the materials was verified by ultrasonic testing. Specimens with a length of 79 mm were cut off from the rods and forged by using a two-staged process. After the first step (Heading), the Mg core was removed partially by drilling to ensure a complete enclosing of the remaining Mg during the second forging step (Net shape forging). The geometry of the drilling hole and the heading die design were dimensioned with the Finite Element-simulation software FORGE. Hence, a complete Al-enclosed Mg component was achieved by using the described process chain and forming processes. Microstructural investigations confirm the formation of an intermetallic interface as expected. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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13 pages, 3322 KiB  
Article
Microstructural Evolution during Severe Plastic Deformation by Gradation Extrusion
by Philipp Frint, Markus Härtel, René Selbmann, Dagmar Dietrich, Markus Bergmann, Thomas Lampke, Dirk Landgrebe and Martin F.X. Wagner
Metals 2018, 8(2), 96; https://doi.org/10.3390/met8020096 - 27 Jan 2018
Cited by 18 | Viewed by 3833
Abstract
In this contribution, we study the microstructural evolution of an age-hardenable AA6082 aluminum alloy during severe plastic deformation by gradation extrusion. A novel die design allowing an interruption of processing and nondestructive billet removal was developed. A systematic study on the microstructure gradient [...] Read more.
In this contribution, we study the microstructural evolution of an age-hardenable AA6082 aluminum alloy during severe plastic deformation by gradation extrusion. A novel die design allowing an interruption of processing and nondestructive billet removal was developed. A systematic study on the microstructure gradient at different points of a single billet could be performed with the help of this die. Distinct gradients were investigated using microhardness measurements and electron microscopy. Our results highlight that gradation extrusion is a powerful method to produce graded materials with partially ultrafine-grained microstructures. From the point of view of obtaining an ultrafine-grained surface layer with maximum hardness, only a small number of forming elements is needed. It was also found that large incremental deformation by too many forming elements may result in locally heterogeneous microstructures and failure near the billet surface caused by localization of deformation. Furthermore, considering economical aspects of processing, fewer forming elements are preferred since several processing parameter-related cost factors are then significantly lower. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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9 pages, 3229 KiB  
Article
Roller Burnishing of Particle Reinforced Aluminium Matrix Composites
by Andreas Nestler and Andreas Schubert
Metals 2018, 8(2), 95; https://doi.org/10.3390/met8020095 - 27 Jan 2018
Cited by 15 | Viewed by 4046
Abstract
Energy and resource efficient systems often demand the use of light-weight materials with a specific combination of properties. However, these requirements usually cannot be achieved with homogeneous materials. Consequently, composites enabling tailored properties gain more and more importance. A special kind of these [...] Read more.
Energy and resource efficient systems often demand the use of light-weight materials with a specific combination of properties. However, these requirements usually cannot be achieved with homogeneous materials. Consequently, composites enabling tailored properties gain more and more importance. A special kind of these materials is aluminium matrix composites (AMCs), which offer elevated strength and wear resistance in comparison to the matrix alloy. However, machining of these materials involves high tool wear and surface imperfections. An approach to producing high-quality surfaces consists in roller burnishing of AMCs. Furthermore, such forming technologies allow for the generation of strong compressive residual stresses. The investigations address the surface properties in the roller burnishing of AMCs by applying different contact forces and feeds. For the experiments, specimens of the alloy AA2124 reinforced with 25% volume proportion of SiC particles are used. Because of the high hardness of the ceramic particles, roller bodies were manufactured from cemented carbide. The results show that roller burnishing enables the generation of smooth surfaces with strong compressive residual stresses in the matrix alloy. The lowest surface roughness values are achieved with the smallest feed (0.05 mm) and the highest contact force (750 N) tested. Such surfaces are supposed to be beneficial for components exposed to dynamic loads. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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13 pages, 4119 KiB  
Article
On the PLC Effect in a Particle Reinforced AA2017 Alloy
by Markus Härtel, Christian Illgen, Philipp Frint and Martin Franz-Xaver Wagner
Metals 2018, 8(2), 88; https://doi.org/10.3390/met8020088 - 25 Jan 2018
Cited by 28 | Viewed by 5089
Abstract
The Portevin–Le Châtelier (PLC) effect often results in serrated plastic flow during tensile testing of aluminum alloys. Its magnitude and characteristics are often sensitive to a material’s heat treatment condition and to the applied strain rate and deformation temperature. In this study, we [...] Read more.
The Portevin–Le Châtelier (PLC) effect often results in serrated plastic flow during tensile testing of aluminum alloys. Its magnitude and characteristics are often sensitive to a material’s heat treatment condition and to the applied strain rate and deformation temperature. In this study, we analyze the plastic deformation behavior of an age-hardenable Al-Cu alloy (AA2017) and of a particle reinforced AA2017 alloy (10 vol. % SiC) in two different conditions: solid solution annealed (W) and naturally aged (T4). For the W-condition of both materials, pronounced serrated flow is observed, while both T4-conditions do not show distinct serrations. It is also found that a reduction of the testing temperature (−60 °C, −196 °C) shifts the onset of serrations to larger plastic strains and additionally reduces their amplitude. Furthermore, compressive jump tests (with alternating strain rates) at room temperature confirm a negative strain rate sensitivity for the W-condition. The occurring PLC effect, as well as the propagation of the corresponding PLC bands in the W-condition, is finally characterized by digital image correlation (DIC) and by acoustic emission measurements during tensile testing. The formation of PLC bands in the reinforced material is accompanied by distinct stress drops as well as by perceptible acoustic emission, and the experimental results clearly show that only type A PLC bands occur during testing at room temperature (RT). Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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10 pages, 22299 KiB  
Article
On the Effect of Natural Aging Prior to Low Temperature ECAP of a High-Strength Aluminum Alloy
by Sebastian Fritsch and Martin Franz-Xaver Wagner
Metals 2018, 8(1), 63; https://doi.org/10.3390/met8010063 - 18 Jan 2018
Cited by 12 | Viewed by 6641
Abstract
Severe plastic deformation (SPD) can be used to generate ultra-fine grained microstructures and thus to increase the strength of many materials. Unfortunately, high strength aluminum alloys are generally hard to deform, which puts severe limits on the feasibility of conventional SPD methods. In [...] Read more.
Severe plastic deformation (SPD) can be used to generate ultra-fine grained microstructures and thus to increase the strength of many materials. Unfortunately, high strength aluminum alloys are generally hard to deform, which puts severe limits on the feasibility of conventional SPD methods. In this study, we use low temperature equal-channel angular pressing (ECAP) to deform an AA7075 alloy. We perform ECAP in a custom-built, cooled ECAP-tool with an internal angle of 90° at −60 °C and with an applied backpressure. In previous studies, high-strength age hardening aluminum alloys were deformed in a solid solution heat treated condition to improve the mechanical properties in combination with subsequent (post-ECAP) aging. In the present study, we systematically vary the initial microstructure—i.e., the material condition prior to low temperature ECAP—by (pre-ECAP) natural aging. The key result of the present study is that precipitates introduced prior to ECAP speed up grain refinement during ECAP. Longer aging times lead to accelerated microstructural evolution, to increasing strength, and to a transition in fracture behavior after a single pass of low temperature ECAP. These results demonstrate the potential of these thermo-mechanical treatments to produce improved properties of high-strength aluminum alloys. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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18 pages, 8793 KiB  
Article
Strain Localization during Equal-Channel Angular Pressing Analyzed by Finite Element Simulations
by Tobias Daniel Horn, Christian Bert Silbermann, Philipp Frint, Martin Franz-Xaver Wagner and Jörn Ihlemann
Metals 2018, 8(1), 55; https://doi.org/10.3390/met8010055 - 15 Jan 2018
Cited by 14 | Viewed by 5521
Abstract
Equal-Channel Angular Pressing (ECAP) is a method used to introduce severe plastic deformation into a metallic billet without changing its geometry. In special cases, strain localization occurs and a pattern consisting of regions with high and low deformation (so-called shear and matrix bands) [...] Read more.
Equal-Channel Angular Pressing (ECAP) is a method used to introduce severe plastic deformation into a metallic billet without changing its geometry. In special cases, strain localization occurs and a pattern consisting of regions with high and low deformation (so-called shear and matrix bands) can emerge. This paper studies this phenomenon numerically adopting two-dimensional finite element simulations of one ECAP pass. The mechanical behavior of aluminum is modeled using phenomenological plasticity theory with isotropic or kinematic hardening. The effects of the two different strain hardening types are investigated numerically by systematic parameter studies: while isotropic hardening only causes minor fluctuations in the plastic strain fields, a material with high initial hardening rate and sufficient strain hardening capacity can exhibit pronounced localized deformation after ECAP. The corresponding finite element simulation results show a regular pattern of shear and matrix bands. This result is confirmed experimentally by ECAP-processing of AA6060 material in a severely cold worked condition, where microstructural analysis also reveals the formation of shear and matrix bands. Excellent agreement is found between the experimental and numerical results in terms of shear and matrix band width and length scale. The simulations provide additional insights regarding the evolution of the strain and stress states in shear and matrix bands. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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9 pages, 6123 KiB  
Article
Influence of Extrusion Temperature on the Aging Behavior and Mechanical Properties of an AA6060 Aluminum Alloy
by Nadja Berndt, Philipp Frint and Martin F.-X. Wagner
Metals 2018, 8(1), 51; https://doi.org/10.3390/met8010051 - 12 Jan 2018
Cited by 18 | Viewed by 6232
Abstract
Processing of AA6060 aluminum alloys for semi-products usually includes hot extrusion with subsequent artificial aging for several hours. Processing below the recrystallization temperature allows for an increased strength at a significantly reduced annealing time by combining strain hardening and precipitation hardening. In this [...] Read more.
Processing of AA6060 aluminum alloys for semi-products usually includes hot extrusion with subsequent artificial aging for several hours. Processing below the recrystallization temperature allows for an increased strength at a significantly reduced annealing time by combining strain hardening and precipitation hardening. In this study, we investigate the potential of cold and warm extrusion as alternative processing routes for high strength aluminum semi-products. Cast billets of the age hardening aluminum alloy AA6060 were solution annealed and then extruded at room temperature, 120 or 170 °C, followed by an aging treatment. Electron microscopy and mechanical testing were performed on the as-extruded as well as the annealed materials to characterize the resulting microstructural features and mechanical properties. All of the extruded profiles exhibit similar, strongly graded microstructures. The strain gradients and the varying extrusion temperatures lead to different stages of dynamic precipitation in the as-extruded materials, which significantly alter the subsequent aging behavior and mechanical properties. The experimental results demonstrate that extrusion below recrystallization temperature allows for high strength at a massively reduced aging time due to dynamic precipitation and/or accelerated precipitation kinetics. The highest strength and ductility were achieved by extrusion at 120 °C and subsequent short-time aging. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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10 pages, 7207 KiB  
Article
Temperature and Particle Size Influence on the High Cycle Fatigue Behavior of the SiC Reinforced 2124 Aluminum Alloy
by Lisa Winter, Kristin Hockauf and Thomas Lampke
Metals 2018, 8(1), 43; https://doi.org/10.3390/met8010043 - 10 Jan 2018
Cited by 11 | Viewed by 4160
Abstract
In this work the high cycle fatigue behavior of a particulate reinforced 2124 aluminum alloy, manufactured by powder metallurgy, is investigated. SiC particles with a size of 3 μm and 300 nm and a volume fraction of 5 and 25 vol %, respectively, [...] Read more.
In this work the high cycle fatigue behavior of a particulate reinforced 2124 aluminum alloy, manufactured by powder metallurgy, is investigated. SiC particles with a size of 3 μm and 300 nm and a volume fraction of 5 and 25 vol %, respectively, were used as reinforcement component. The present study is focused on the fatigue strength and the influence of particle size and temperature. Systematic work is done by comparing the unreinforced alloy and the reinforced conditions. All of the material conditions are characterized by electron microscopy and tensile and fatigue testing at room temperature and at 180 °C. With an increase in temperature the tensile and the fatigue strength decrease, regardless of particle size and volume fraction due to the lower matrix strength. The combination of 25 vol % SiC particle fraction with 3 μm size proved to be most suitable to achieve a major fatigue performance at room temperature and at 180 °C. The fatigue strength is increased by 40% when compared to the unreinforced alloy, as it is assumed the interparticle spacing for this condition reaches a critical value then. Full article
(This article belongs to the Special Issue Scientific and Engineering Progress on Aluminum-Based Light-Weight Materials: Research Reports from the German Collaborative Research Center 692)
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