Special Issue "Material and Process Design for Lightweight Structures"

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

Deadline for manuscript submissions: closed (31 December 2018)

Special Issue Editor

Guest Editor
Dr.-Ing. Talal Al-Samman

RWTH Aachen University, Institute of Physical Metallurgy and Metal Physics (IMM), Aachen, Germany
Website | E-Mail
Interests: lightweight materials; magnesium alloys; plastic deformation; recrystallization and grain growth; texture and microstructure; mechanical properties

Special Issue Information

Dear Colleagues,

The drive toward increased fuel efficiency and a reduction in the harmful emission of greenhouse gases associated with energy generation and transportation has led, in recent years, to a resurgence of interest in light alloys and new lightweight alloy design strategies. In automotive industry, the need to reduce vehicle weight has led to extensive research efforts to develop aluminum and magnesium alloys for structural car body parts. In aerospace, the move toward composite airframe structures demands an increased use of formable titanium alloys. In steel research, there are also major efforts to design novel damage-controlled forming processes for a new generation of efficient and reliable lightweight steel components. These materials constitute today’s research mission for lightweight design. They provide a fertile materials science research field aiming to achieve a better understanding of the interplay between industrial processing, developing microstructures, and the resulting material properties.

Given the extensive scientific and technological importance of this timely subject, it is expedient to collect concise reports—to be presented in this Special Issue—on the current status in the field in the areas of manufacturing and processing technologies of light metals, microstructure and texture manipulation, innovative alloy design concepts and advanced characterization methods and in-situ techniques. We will not be able to cover all the exciting work in this rapidly-growing field, but we certainly hope to provide the reader with a sense of where significant advances are being made, where critical issues remain unanswered, and, from the authors’ perspectives, where the field is heading in the near future.

Dr.-Ing. Talal Al-Samman
Guest Editor

Manuscript Submission Information

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Keywords

  • light metals
  • magnesium
  • aluminum
  • titanium
  • alloy design
  • microstructure
  • damage
  • processing
  • mechanical properties
  • advanced characterization

Published Papers (11 papers)

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Editorial

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Open AccessEditorial
Material and Process Design for Lightweight Structures
Metals 2019, 9(4), 415; https://doi.org/10.3390/met9040415
Received: 29 March 2019 / Accepted: 4 April 2019 / Published: 6 April 2019
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Abstract
The ever-rising demand for increased fuel efficiency and a reduction in the harmful emission of greenhouse gases associated with energy generation and transportation has led, in recent years, to a resurgence of interest in light materials and new lightweight design strategies [...] Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)

Research

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Open AccessArticle
Global and High-Resolution Damage Quantification in Dual-Phase Steel Bending Samples with Varying Stress States
Metals 2019, 9(3), 319; https://doi.org/10.3390/met9030319
Received: 31 January 2019 / Revised: 1 March 2019 / Accepted: 6 March 2019 / Published: 12 March 2019
Cited by 1 | PDF Full-text (6132 KB) | HTML Full-text | XML Full-text
Abstract
In a variety of modern, multi-phase steels, damage evolves during plastic deformation in the form of the nucleation, growth and coalescence of voids in the microstructure. These microscopic sites play a vital role in the evolution of the materials’ mechanical properties, and therefore [...] Read more.
In a variety of modern, multi-phase steels, damage evolves during plastic deformation in the form of the nucleation, growth and coalescence of voids in the microstructure. These microscopic sites play a vital role in the evolution of the materials’ mechanical properties, and therefore the later performance of bent products, even without having yet led to macroscopic cracking. However, the characterization and quantification of these diminutive sites is complex and time-consuming, especially when areas large enough to be statistically relevant for a complete bent product are considered. Here, we propose two possible solutions to this problem: an advanced, SEM-based method for high-resolution, large-area imaging, and an integral approach for calculating the overall void volume fraction by means of density measurement. These are applied for two bending processes, conventional air bending and radial stress superposed bending (RSS bending), to investigate and compare the strain- and stress-state dependent void evolution. RSS bending reduces the stress triaxiality during forming, which is found to diminish the overall formation of damage sites and their growth by the complimentary characterization approaches of high-resolution SEM and global density measurements. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessFeature PaperArticle
A Mathematical Model of Deformation under High Pressure Torsion Extrusion
Metals 2019, 9(3), 306; https://doi.org/10.3390/met9030306
Received: 16 January 2019 / Revised: 26 February 2019 / Accepted: 4 March 2019 / Published: 8 March 2019
Cited by 1 | PDF Full-text (1823 KB) | HTML Full-text | XML Full-text
Abstract
High pressure torsion extrusion (HPTE) is a promising new mechanism for severe plastic deformation of metals and alloys. It enables the manufacture of long products with a radial gradient ultrafine-grained structure and of composite materials with a helical inner architecture at the meso [...] Read more.
High pressure torsion extrusion (HPTE) is a promising new mechanism for severe plastic deformation of metals and alloys. It enables the manufacture of long products with a radial gradient ultrafine-grained structure and of composite materials with a helical inner architecture at the meso and the macro scale. HPTE is very promising as a technique enabling light weighting, especially with magnesium, aluminium and titanium alloys. For the first time, this article presents an analytical model of the HPTE process that makes it possible to investigate the role of the various process parameters and calculate the distribution of the equivalent strain over the entire sample length. To verify the model, its predictions were compared with the numerical simulations by employing the finite element software QForm. It was shown that potential negative effects associated with the slippage of a sample relative to the container walls can be suppressed through appropriate die design and an efficient use of the friction forces. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Experimental and Numerical Study of an Automotive Component Produced with Innovative Ceramic Core in High Pressure Die Casting (HPDC)
Metals 2019, 9(2), 217; https://doi.org/10.3390/met9020217
Received: 14 December 2018 / Revised: 7 February 2019 / Accepted: 8 February 2019 / Published: 12 February 2019
Cited by 1 | PDF Full-text (15759 KB) | HTML Full-text | XML Full-text
Abstract
Weight reduction and material substitution are increasing trends in the automotive industry. High pressure die casting (HPDC) is the conventional casting technology for the high volume production of light alloys; it has recently found wide application in the manufacturing of critical components, such [...] Read more.
Weight reduction and material substitution are increasing trends in the automotive industry. High pressure die casting (HPDC) is the conventional casting technology for the high volume production of light alloys; it has recently found wide application in the manufacturing of critical components, such as complex and thin geometry automotive parts. However, the major restriction of this affordable technology is the difficulty to design and realize hollow sections or components with undercuts. An innovative way to further increase the competitiveness of HPDC is to form complex undercut shaped parts through the use of new lost cores that are able endure the high pressures used in HPDC. This paper investigates the use of innovative ceramic lost cores in the production of a passenger car aluminum crossbeam by HPDC. Firstly, process and structural simulations were performed to improve the crossbeam design and check the technology features. The results led to the selection of the process parameters and the production of some prototypes that were finally characterized. These analyses demonstrate the feasibility of the production of hollow components by HPDC using ceramic cores. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Multilayered-Sheet Hot Stamping and Application in Electric-Power-Fitting Products
Metals 2019, 9(2), 215; https://doi.org/10.3390/met9020215
Received: 8 January 2019 / Revised: 1 February 2019 / Accepted: 8 February 2019 / Published: 12 February 2019
Cited by 1 | PDF Full-text (8721 KB) | HTML Full-text | XML Full-text
Abstract
Traditional electric transmission line fittings, which are always manufactured from thick metal slabs, possess the disadvantage of heavy weight. In this study, a new type of electrical-connection-fitting, clevis-clevis component made of high-strength steel is developed to reduce weight, and a new hot-stamping process [...] Read more.
Traditional electric transmission line fittings, which are always manufactured from thick metal slabs, possess the disadvantage of heavy weight. In this study, a new type of electrical-connection-fitting, clevis-clevis component made of high-strength steel is developed to reduce weight, and a new hot-stamping process for multilayered sheets is proposed to manufacture the component efficiently. First, the structure of the new clevis-clevis component is designed, and the corresponding tool is developed. Second, a flat-tool heat transfer experiment is conducted. The influence of the number of layers and contact pressure on the cooling rate of each sheet is investigated. The optimizing number of layers and contact pressure for the multilayered-sheet, hot-stamping process are obtained. The optimal number of layers is two, and the optimal contact pressure is more than 20 MPa. The final microstructure of each sheet is fully martensitic, and the strength is about 1500 MPa. Finally, U-shaped, double-layer-sheet hot stamping is implemented to produce a typical electrical-connection-fitting, clevis-clevis component. The bearing capacity of a four-layered clevis-clevis is tested through numerical and experimental methods. The new connection-fitting clevis-clevis component exhibits a high load capacity of 280 kN. Compared with that of the traditional component, the weight of the new component is reduced by 60%. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Modification of Microstructure and Texture in Highly Non-Flammable Mg-Al-Zn-Y-Ca Alloy Sheets by Controlled Thermomechanical Processes
Metals 2019, 9(2), 181; https://doi.org/10.3390/met9020181
Received: 28 December 2018 / Revised: 27 January 2019 / Accepted: 28 January 2019 / Published: 2 February 2019
Cited by 1 | PDF Full-text (4016 KB) | HTML Full-text | XML Full-text
Abstract
The influence of rolling temperature and pass reduction degree on microstructure and texture evolution was investigated using an AZXW3100 alloy, Mg-3Al-1Zn-0.5Ca-0.5Y, in wt.%. The change in the rolling schedule had a significant influence on the resulting texture and microstructure from the rolling and [...] Read more.
The influence of rolling temperature and pass reduction degree on microstructure and texture evolution was investigated using an AZXW3100 alloy, Mg-3Al-1Zn-0.5Ca-0.5Y, in wt.%. The change in the rolling schedule had a significant influence on the resulting texture and microstructure from the rolling and subsequent annealing. A relatively strong basal-type texture with a basal pole split into the rolling direction was formed by rolling at 450 °C with a decreasing scheme of the pass reduction degrees with a rolling step, while the tilted basal poles in the transverse direction were developed by using an increasing scheme of the pass reduction degrees. Rolling at 500 °C results in a further distinct texture type with a far more largely tilted basal pole into the rolling direction. The directional anisotropy of the mechanical properties in the annealed sheets was caused by the texture and microstructural features, which were in turn influenced by the rolling condition. The Erichsen index of the sheets varied in accordance to the texture sharpness, i.e., the weaker the texture the higher the formability. The sheet with a tetrarchy distribution of the basal poles into the transverse and rolling directions shows an excellent formability with an average Erichsen index of 8.1. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Effect of Surface Roughness on the Bonding Strength and Spring-Back of a CFRP/CR980 Hybrid Composite
Metals 2018, 8(9), 716; https://doi.org/10.3390/met8090716
Received: 12 July 2018 / Revised: 2 September 2018 / Accepted: 10 September 2018 / Published: 12 September 2018
Cited by 1 | PDF Full-text (4782 KB) | HTML Full-text | XML Full-text
Abstract
Carbon fiber-reinforced plastic (CFRP), which is a light and composite material, has a higher specific strength and stiffness than metal materials. However, owing to its low elongation, it is vulnerable to local impacts such as collision. Therefore, hybrid composite materials that can overcome [...] Read more.
Carbon fiber-reinforced plastic (CFRP), which is a light and composite material, has a higher specific strength and stiffness than metal materials. However, owing to its low elongation, it is vulnerable to local impacts such as collision. Therefore, hybrid composite materials that can overcome the disadvantages of homogeneous materials by bonding CFRP and metal materials are increasingly popular. In this study, a physical surface treatment sandblast process was applied on a high tensile steel plate (CR980) manufactured by cold rolling to form another surface condition, and the bonding strength with CFRP was measured. In addition, spring-back due to the manufacturing process of the CFRP and CR980 hybrid composite material bonded with different surface roughness was observed. The bonding strength and the spring-back angle of the CFRP/CR980 hybrid composite material tended to increase with the increase in the surface roughness. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422)
Metals 2018, 8(6), 463; https://doi.org/10.3390/met8060463
Received: 12 May 2018 / Revised: 9 June 2018 / Accepted: 13 June 2018 / Published: 18 June 2018
Cited by 2 | PDF Full-text (6154 KB) | HTML Full-text | XML Full-text
Abstract
With a view to design connected processing steps for the manufacturing of components, the hot working behavior of the ABaX422 alloy has been characterized for the as-cast and extruded conditions. In the as-cast condition, the alloy has a limited workability, due to the [...] Read more.
With a view to design connected processing steps for the manufacturing of components, the hot working behavior of the ABaX422 alloy has been characterized for the as-cast and extruded conditions. In the as-cast condition, the alloy has a limited workability, due to the presence of a large volume of intermetallic phases at the grain boundaries, and is not suitable to process at high speeds. A connected processing step has been designed on the basis of the results of the processing map for the as-cast alloy, and this step involves the extrusion of the cast billet to obtain a 12 mm diameter rod product at a billet temperature of 390 °C and at a ram speed of 1 mm s−1. The microstructure of the extruded rod has a finer grain size, with redistributed fine particles of the intermetallic phases. The processing map of the extruded rod exhibited two new domains, and the one in the temperature range 360–420 °C and strain rate range 0.2–10 s−1 is useful for manufacturing at high speeds, while the lower temperature develops a finer grain size in the product to improve the room temperature strength and ductility. The area of the flow instability is also reduced by the extrusion step, widening the workability window. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Assessment of Metal Flow Balance in Multi-Output Porthole Hot Extrusion of AA6060 Thin-Walled Profile
Metals 2018, 8(6), 462; https://doi.org/10.3390/met8060462
Received: 15 May 2018 / Revised: 9 June 2018 / Accepted: 10 June 2018 / Published: 18 June 2018
Cited by 2 | PDF Full-text (6078 KB) | HTML Full-text | XML Full-text
Abstract
For the porthole hot extrusion of a thin-walled tube based on metal flow, the role of the die’s structure should be focused on to achieve precision formation, especially for multi-output extrusion and/or complex cross-sectional profiles. In order to obtain a better metal flow [...] Read more.
For the porthole hot extrusion of a thin-walled tube based on metal flow, the role of the die’s structure should be focused on to achieve precision formation, especially for multi-output extrusion and/or complex cross-sectional profiles. In order to obtain a better metal flow balance, a multi-output porthole extrusion die was developed, including some novel features such as a circular pattern of the portholes with a dart-shaped inlet bridge, a buckle angle in the inlet side of the upper die, a two-step welding chamber, and a non-uniform bearing length distribution. Through the use of thermo-mechanical modeling combined with the Taguchi method, the underlying effects of key die features were investigated, such as the billet buckle angle, the porthole bevel angle, the depth of the welding chamber, and the type of bridge on the metal flow balance. The experimental validation showed that the developed numerical model for the multi-output porthole extrusion process had high prediction accuracy, and was acceptable for use in an industrial extrusion with a complex section. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Effect of Process Parameters on Fatigue and Fracture Behavior of Al-Cu-Mg Alloy after Creep Aging
Metals 2018, 8(5), 298; https://doi.org/10.3390/met8050298
Received: 2 April 2018 / Revised: 18 April 2018 / Accepted: 21 April 2018 / Published: 26 April 2018
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Abstract
A set of creep aging tests at different aging temperatures and stress levels were carried out for Al-Cu-Mg alloy, and the effects of creep aging on strength and fatigue fracture behavior were studied through tensile tests and fatigue crack propagation tests. The microstructures [...] Read more.
A set of creep aging tests at different aging temperatures and stress levels were carried out for Al-Cu-Mg alloy, and the effects of creep aging on strength and fatigue fracture behavior were studied through tensile tests and fatigue crack propagation tests. The microstructures were further analyzed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that temperature and stress can obviously affect the creep behavior, mechanical properties, and fatigue life of Al-Cu-Mg alloy. As the aging temperature increases, the fatigue life of alloy first increases, and then decreases. The microstructure also displays a transition from the Guinier-Preston-Bagaryatsky (GPB) zones to the precipitation of S phase in the grain interior. However, the precipitation phases grow up and become coarse at excessive temperatures. Increasing stress can narrow the precipitation-free zone (PFZ) at the grain boundary and improve the fatigue life, but overhigh stress can produce the opposite result. In summary, the fatigue life of Al-Cu-Mg alloy can be improved by fine-dispersive precipitation phases and a narrow PFZ in a suitable creep aging process. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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Open AccessArticle
Experimental Investigations of the In-Die Quenching Efficiency and Die Surface Temperature of Hot Stamping Aluminium Alloys
Metals 2018, 8(4), 231; https://doi.org/10.3390/met8040231
Received: 28 February 2018 / Revised: 24 March 2018 / Accepted: 27 March 2018 / Published: 2 April 2018
Cited by 1 | PDF Full-text (9304 KB) | HTML Full-text | XML Full-text
Abstract
The in-die quenching is a key stage in the hot stamping volume production chain which determines the post-formed strength of lightweight alloy components, tool life, and hot stamping productivity. In this paper, the performance of in-die quenching, reflected by the quenching efficiency (the [...] Read more.
The in-die quenching is a key stage in the hot stamping volume production chain which determines the post-formed strength of lightweight alloy components, tool life, and hot stamping productivity. In this paper, the performance of in-die quenching, reflected by the quenching efficiency (the time of work-piece held within stamping dies) and die surface temperature during the simulated hot stamping process of AA6082, was experimentally and analytically investigated. A range of in-die quenching experiments were performed for different initial work-piece and die temperatures, quenching pressures, work-piece thickness, and die clearances, under hot stamping conditions. In addition, a one-dimensional (1D) closed-form heat transfer model was used to calculate the die surface temperature evolution that is difficult to obtain during practical manufacture situations. The results have shown that the in-die quenching efficiency can be significantly increased by decreasing the initial work-piece and die temperatures. Die clearances are required to be designed precisely to obtain sufficiently high quenching rates and satisfying post-formed strength for hot-stamped panel components. This study systematically considered an extensive variety of influencing factors on the in-die quenching performance, which can provide practical guides for stamping tool designers and manufacture systems for hot-stamping volume production. Full article
(This article belongs to the Special Issue Material and Process Design for Lightweight Structures)
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