Lightweight Alloys for Aerospace Applications

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

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 13680

Special Issue Editors


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Guest Editor
Department of Industrial Engineering, University of Rome Tor Vergata, via del Politecnico, 1-00133 Rome, Italy
Interests: materials characterizations; X-ray diffraction; scanning electron microscopy
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
University of Rome-Tor Vergata, Rome, Italy
Interests: the materials for aerospace applications; the structure of liquid metals; solidification; welding; the indentation tests
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The strong competition in the industrial aerospace sector pushes towards the production of aircrafts with reduced operating costs through an extended service life, better fuel efficiency, and increased payload and flight range. In this perspective, there is an increasing demand of new materials and/or materials with improved characteristics to reduce the weight of mechanical components and structures; thus, lightweight alloys and their composites play a key role.

Light metal alloys are largely used in the structural parts of aircrafts and cold sections of engines (fan, compressor, and casing). In recent years, breakthrough advancements have been made for improving the mechanical performances and corrosion resistance of aluminum, magnesium, and titanium alloys by means of composition tailoring, grain refinement, precipitation of second phases, and control of microstructural features on a nanoscale.

Moreover, the sustainable technological development has become a dominant paradigm today and imposes an optimized use of resources, a lower energetic impact of industrial processes, and new tasks for materials and products.

New results are continuously published in the scientific literature. The Special Issue aims to collect both review and research papers from academic and industrial investigators focused on recent advancements in lightweight alloys, novel processes, and testing methods for aerospace applications. We hope this could be a way to stimulate fruitful networking on an international scale and cooperation among authors and readers operating in this research area.

Dr. Alessandra Varone
Prof. Dr. Roberto Montanari
Guest Editors

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Keywords

  • Light alloys
  • Aerospace
  • Mechanical properties
  • Corrosion resistance
  • Testing methods

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Published Papers (5 papers)

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Research

12 pages, 4687 KiB  
Article
Towards Qualification in the Aviation Industry: Impact Toughness of Ti6Al4V(ELI) Specimens Produced through Laser Powder Bed Fusion Followed by Two-Stage Heat Treatment
by Lehlohonolo Francis Monaheng, Willie Bouwer du Preez and Claudia Polese
Metals 2021, 11(11), 1736; https://doi.org/10.3390/met11111736 - 30 Oct 2021
Cited by 11 | Viewed by 2779
Abstract
Laser powder bed fusion (L-PBF) has the potential to be applied in the production of titanium aircraft components with good mechanical properties, provided the technology has been qualified and accepted in the aviation industry. To achieve acceptance of the L-PBF technology in the [...] Read more.
Laser powder bed fusion (L-PBF) has the potential to be applied in the production of titanium aircraft components with good mechanical properties, provided the technology has been qualified and accepted in the aviation industry. To achieve acceptance of the L-PBF technology in the aircraft industry, mechanical property data needed for the qualification process must be generated according to accepted testing standards. The impact toughness of Ti6Al4V extra low interstitial (ELI) specimens, produced through L-PBF followed by annealing, was investigated in this study. Charpy impact testing complying with American Standard Test Method (ASTM) E23 was performed with specimens annealed and conditioned at low temperature. On average, the toughness recorded for the specimens with 3D-printed and machined V-notches was 28 J and 31 J, respectively. These results are higher than the 24 J required in the aerospace industry. Finally, fractographic analyses of the fracture surfaces of the specimens were performed to determine the fracture mechanism of the Ti6Al4V(ELI) impact specimens. Full article
(This article belongs to the Special Issue Lightweight Alloys for Aerospace Applications)
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18 pages, 44461 KiB  
Article
Biaxial Experiments and Numerical Analysis on Stress-State-Dependent Damage and Failure Behavior of the Anisotropic Aluminum Alloy EN AW-2017A
by Michael Brünig, Steffen Gerke and Sanjeev Koirala
Metals 2021, 11(8), 1214; https://doi.org/10.3390/met11081214 - 30 Jul 2021
Cited by 12 | Viewed by 1757
Abstract
Many experiments indicated the remarkable dependence of the strength and failure behavior of anisotropic ductile metals on the loading direction and on the stress state. These influences have to be taken into account in accurate material models and in the numerical simulation of [...] Read more.
Many experiments indicated the remarkable dependence of the strength and failure behavior of anisotropic ductile metals on the loading direction and on the stress state. These influences have to be taken into account in accurate material models and in the numerical simulation of complex loading processes predicting the safety and lifetime of aerospace structures. Therefore, the present paper discusses the effect of loading direction and stress state on the damage and failure behavior of the anisotropic aluminum alloy EN AW-2017A. Experiments and corresponding numerical analysis with the newly developed, biaxially loaded X0 specimen have been performed and the influence of different load ratios is examined. The formation of strain fields in critical parts of the X0 specimen is monitored by digital image correlation. Different failure modes are visualized by scanning electron microscopy of fracture surfaces. Stress states are predicted by finite element calculations and they are used to explain damage and fracture processes at the micro-level. The experimental–numerical analysis shows that the loading direction and the stress state remarkably affect the evolution of the width and orientation of localized strain fields as well as the formation of damage processes and fracture modes. As a consequence, characterization of anisotropic metals is highly recommended to be based on an enhanced experimental program with biaxial tests including different load ratios and loading directions. Full article
(This article belongs to the Special Issue Lightweight Alloys for Aerospace Applications)
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15 pages, 8429 KiB  
Article
Simulation and Experimental Investigation of Granular Medium Forming Technology on Titanium Alloy Sheet at 500 °C
by Gaoshen Cai, Jubo Fu, Chuanyu Wu, Kangning Liu and Lihui Lang
Metals 2021, 11(1), 114; https://doi.org/10.3390/met11010114 - 8 Jan 2021
Cited by 5 | Viewed by 2162
Abstract
To investigate and verify the degree to which the forming properties of low plasticity materials are improved at room temperature using the granular medium forming (GMF) process at 500 °C, a coupled Eulerian–Lagrangian unit calculation model was established and a special mold was [...] Read more.
To investigate and verify the degree to which the forming properties of low plasticity materials are improved at room temperature using the granular medium forming (GMF) process at 500 °C, a coupled Eulerian–Lagrangian unit calculation model was established and a special mold was designed to conduct a GMF experiment for titanium alloy sheets under different-shaped pressing blocks. Then, using a three-coordinate measuring machine, the sizes of the outer contours of the parts formed at room temperature were measured, and the results showed that the bottom of the parts maintained a smooth surface during the drawing process. As the drawing height increased, the radius of curvature of the cambered surface gradually decreased. By measuring the wall thickness of the parts at different positions from the central axis using a caliper, the wall thickness distribution curves of these parts were obtained, which showed that the deformations of the bottom of the formed parts were uniform and the uniformity of the wall thickness distribution was good. By comparing the GMF experimental data at 500 °C with traditional deep drawing experimental data, it was found that the GMF technology could improve the forming properties of low plastic materials such as titanium alloys. Full article
(This article belongs to the Special Issue Lightweight Alloys for Aerospace Applications)
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15 pages, 12419 KiB  
Article
Dislocation Breakaway Damping in AA7050 Alloy
by Andrea Di Schino, Roberto Montanari, Claudio Testani and Alessandra Varone
Metals 2020, 10(12), 1682; https://doi.org/10.3390/met10121682 - 16 Dec 2020
Cited by 5 | Viewed by 2525
Abstract
The AA7050 alloy prepared through the standard industrial hot-forging cycle has been investigated by means of isothermal mechanical spectroscopy (MS) from room temperature up to 185 °C. Each MS test consisted of a cycle with two stages, at increasing and decreasing strain. After [...] Read more.
The AA7050 alloy prepared through the standard industrial hot-forging cycle has been investigated by means of isothermal mechanical spectroscopy (MS) from room temperature up to 185 °C. Each MS test consisted of a cycle with two stages, at increasing and decreasing strain. After each cycle the damping value resulted to be higher than the original one indicating the occurrence of an irreversible transformation. Such phenomenon, observed for all the test temperatures, becomes more relevant for T ≥ 150 °C. The irreversible transformation has been discussed and explained by considering the evolution of the mean dislocation link length between pinning points represented by nanometric MgZn2 precipitates. The breakaway of dislocation segments from pinning points occurs in the stage at increasing strain and is not fully recovered during the second stage at decreasing strain thus the mean link length increases in a MS test cycle. The onset of thermal activated dislocation cross-slip at about 150 °C favors the dislocation breakaway and consequently enhances the effect on damping. Full article
(This article belongs to the Special Issue Lightweight Alloys for Aerospace Applications)
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18 pages, 4524 KiB  
Article
Numerical Simulation of Buckling and Post-Buckling Behavior of a Central Notched Thin Aluminum Foil with Nonlinearity in Consideration
by Mahdieh Shahmardani, Per Ståhle, Md Shafiqul Islam and Sharon Kao-Walter
Metals 2020, 10(5), 582; https://doi.org/10.3390/met10050582 - 29 Apr 2020
Cited by 5 | Viewed by 3000
Abstract
In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the cracked area. This is due to local buckling and compression stresses near the crack surfaces. This study aims to numerically study the buckling behavior of a thin [...] Read more.
In thin notched sheets under tensile loading, wrinkling appears on the sheet surface, specifically around the cracked area. This is due to local buckling and compression stresses near the crack surfaces. This study aims to numerically study the buckling behavior of a thin sheet with a central crack under tension. A numerical model of a notched sheet under tensile loading is developed using the finite element method, which considers both material and geometrical nonlinearity. To overcome the convergence problem caused by the small thickness-to-length/width ratio and to stimulate the buckling, an imperfection is defined as a small perturbation in the numerical model. Both elastic and elasto-plastic behavior are applied, and the influence of them is studied on the critical buckling stress and the post-buckling behavior of the notched sheet. Numerical results for both elastic and elasto-plastic behavior reflect that very small perturbations need more energy for the activation of buckling mode, and a higher buckling mode is predominant. The influences of different parameters, including Poisson’s ratio, yield limit, crack length-to-sheet-width ratio, and the sheet aspect ratio are also evaluated with a focus on the critical buckling stress and the buckling mode shape. With increase in Poisson’s ratio. First, the critical buckling stress reduces and then remains constant. A higher yield limit results in increases in the critical buckling stress, and no change in the buckling mode shape while adopting various crack length-to-sheet-width ratios, and the sheet aspect ratio changes the buckling mode shape. Full article
(This article belongs to the Special Issue Lightweight Alloys for Aerospace Applications)
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