Research

14 pages, 9311 KiB

Open AccessArticle

Microstructure and Properties of a Novel Al-Mg-Si Alloy AA 6086

by Franc Zupanič, Matej Steinacher, Sandi Žist and Tonica Bončina

Metals 2021, 11(2), 368; https://doi.org/10.3390/met11020368 - 23 Feb 2021

Cited by 24 | Viewed by 3674

In this work, we investigated a novel Al-Mg-Si alloy, which was developed from an AA 6082, in order to considerably improve the yield and tensile strengths whilst retain excellent ductility. The new alloy possesses a higher content of Si than specified by AA [...] Read more.

In this work, we investigated a novel Al-Mg-Si alloy, which was developed from an AA 6082, in order to considerably improve the yield and tensile strengths whilst retain excellent ductility. The new alloy possesses a higher content of Si than specified by AA 6082, and, in addition, it contains copper and zirconium. The alloy was characterized in the as-cast condition, after homogenization, extrusion, and T6 heat treatment using light microscopy, scanning and transmission electron microscopy with energy dispersive spectrometry, X-ray diffraction, differential thermal analysis and tensile testing. After T6 temper, tensile strengths were around 490 MPa with more than 10% elongation at fracture. The microstructure consisted of small-grained Al-rich matrix with α-AlMnSi and Al₃Zr dispersoids, and Q′-AlCuMgSi and β-Mg₂Si-type precipitates. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Graphical abstract

12 pages, 4760 KiB

Open AccessArticle

Bimodal Microstructure Obtained by Rapid Solidification to Improve the Mechanical and Corrosion Properties of Aluminum Alloys at Elevated Temperature

by Irena Paulin, Črtomir Donik, Peter Cvahte and Matjaž Godec

Metals 2021, 11(2), 230; https://doi.org/10.3390/met11020230 - 29 Jan 2021

Cited by 2 | Viewed by 1807

Abstract

The demand for aluminum alloys is increasing, as are the demands for higher strength, with the aim of using lighter products for a greener environment. To achieve high-strength, corrosion-resistant aluminum alloys, the melt is rapidly solidified using the melt-spinning technique to form ribbons, [...] Read more.

The demand for aluminum alloys is increasing, as are the demands for higher strength, with the aim of using lighter products for a greener environment. To achieve high-strength, corrosion-resistant aluminum alloys, the melt is rapidly solidified using the melt-spinning technique to form ribbons, which are then plastically consolidated by extrusion at elevated temperature. Different chemical compositions, based on adding the transition-metal elements Mn and Fe, were employed to remain within the limits of the standard chemical composition of the AA5083 alloy. The samples were systematically studied using light microscopy, scanning electron, and transmission microscopy with electron diffraction spectrometry for the micro-chemical analyses. Tensile tests and Vickers microhardness were applied for mechanical analyses, and corrosion tests were performed in a comparison with the standard alloy. The tensile strength was improved by 65%, the yield strength by 45% and elongation by 14%. The mechanism by which we achieved the better mechanical and corrosion properties is explained. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

12 pages, 9769 KiB

Open AccessArticle

Effect of Asymmetric Material Flow on the Microstructure and Mechanical Properties of 5A06 Al-Alloy Welded Joint by VPPA Welding

by Zhaoyang Yan, Shujun Chen, Fan Jiang, Xing Zheng, Ooi Tian, Wei Cheng and Xinqiang Ma

Metals 2021, 11(1), 120; https://doi.org/10.3390/met11010120 - 09 Jan 2021

Cited by 7 | Viewed by 1777

Abstract

The microstructure, texture, and mechanical properties of the asymmetric welded joint in variable polarity plasma arc (VPPA) welding were studied and discussed in this paper. The asymmetric welded joint was obtained through horizontal welding, where the effect of gravity caused asymmetric material flow. [...] Read more.

The microstructure, texture, and mechanical properties of the asymmetric welded joint in variable polarity plasma arc (VPPA) welding were studied and discussed in this paper. The asymmetric welded joint was obtained through horizontal welding, where the effect of gravity caused asymmetric material flow. The results showed that the grain size and low angle grain boundary (LAGB) at both sides of the obtained welded joint were asymmetric; the grain size differed by a factor of 1.3. The average grain size of the Base Metal (BM), Lower-weld zone (WZ) and Upper-WZ were 25.73 ± 1.25, 37.87 ± 1.89 and 49.92 ± 2.49 µm, respectively. There is discrepancy between the main textures in both sides of the welded joint. However, the effect of asymmetric metal flow on the weld texture was not significant. The micro-hardness distribution was inhomogeneous, the lowest hardness was observed in regions with larger grain sizes and smaller low angle grain boundary. During tensile strength tests, the specimens fractured at the position with the lowest hardness although it has reached 89.2% of the strength of the BM. Furthermore, the effect of asymmetric metal flow and underlying causes of asymmetric weld properties in VPPA horizontal welding have been discussed and analyzed. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

20 pages, 8634 KiB

Open AccessArticle

Role of Small Addition of Sc and Zr in Clustering and Precipitation Phenomena Induced in AA7075

by Martin Vlach, Veronika Kodetova, Jakub Cizek, Michal Leibner, Tomáš Kekule, František Lukáč, Miroslav Cieslar, Lucia Bajtošová, Hana Kudrnová, Vladimir Sima, Sebastian Zikmund, Eva Cernoskova, Petr Kutalek, Volkmar-Dirk Neubert and Volkmar Neubert

Metals 2021, 11(1), 8; https://doi.org/10.3390/met11010008 - 23 Dec 2020

Cited by 14 | Viewed by 2192

Abstract

A detailed characterization of phase transformations in the heat-treated commercial 7075 aluminum alloys without/with low Sc–Zr addition was carried out. Mechanical and electrical properties, thermal and corrosion behavior were compared to the microstructure development. The eutectic phase consists of four parts: MgZn₂ [...] Read more.

A detailed characterization of phase transformations in the heat-treated commercial 7075 aluminum alloys without/with low Sc–Zr addition was carried out. Mechanical and electrical properties, thermal and corrosion behavior were compared to the microstructure development. The eutectic phase consists of four parts: MgZn₂ phase, Al₂CuMg phase (S-phase), Al₂Zn₃Mg₃ phase (T-phase), and primary λ-Al(Mn,Fe,Si) phase. Strengthening during non-isothermal (isochronal) annealing is caused by a combination of formation of the GP zones, η’-phase, T-phase and co-presence of the primary and secondary Al₃(Sc,Zr)-phase particles. Positive influence on corrosion properties is owing to the addition of Sc–Zr. Positron annihilation showed an evolution of solute Zn,Mg-(co-)clusters into (precursors of) the GP zones in the course of natural ageing. The concentration of the (co-)clusters is slightly negatively affected by the low Sc–Zr addition. A combination of both precipitation sequences of the Al–Zn–Mg–Cu-based system was observed. The apparent activation energy values for dissolution/formation of the clusters/GP zones and for formation of the metastable η’-phase, stable T-phase and stable η-phase were calculated. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Graphical abstract

17 pages, 8147 KiB

Open AccessArticle

Ultrasonic and Conventional Fatigue Endurance of Aeronautical Aluminum Alloy 7075-T6, with Artificial and Induced Pre-Corrosion

by Ishvari F. Zuñiga Tello, Marijana Milković, Gonzalo M. Domínguez Almaraz and Nenad Gubeljak

Metals 2020, 10(8), 1033; https://doi.org/10.3390/met10081033 - 01 Aug 2020

Cited by 5 | Viewed by 2428

Abstract

Ultrasonic and conventional fatigue tests were carried out on the AISI-SAE AA7075-T6 aluminum alloy, in order to evaluate the effect of artificial and induced pre-corrosion. Artificial pre-corrosion was obtained by two hemispherical pitting holes of 500-μm diameter at the specimen neck section, machined [...] Read more.

Ultrasonic and conventional fatigue tests were carried out on the AISI-SAE AA7075-T6 aluminum alloy, in order to evaluate the effect of artificial and induced pre-corrosion. Artificial pre-corrosion was obtained by two hemispherical pitting holes of 500-μm diameter at the specimen neck section, machined following the longitudinal or transverse direction of the testing specimen. Induced pre-corrosion was achieved using the international standard ESA ECSS-Q-ST-70-37C of the European Space Agency. Specimens were tested under ultrasonic fatigue technique at frequency of 20 kHz and under conventional fatigue at frequency of 20 Hz. The two applied load ratios were: R = −1 in ultrasonic fatigue tests and R = 0.1 in conventional fatigue tests. The main results were the effects of artificial and induced pre-corrosion on the fatigue endurance, together with the surface roughness modification after the conventional fatigue tests. Crack initiation and propagation were analyzed and numeric models were constructed to investigate the stress concentration associated with pre-corrosion pits, together with the evaluation of the stress intensity factor in mode I from crack initiation to fracture. Finally, the stress intensity factor range threshold ΔK_TH was obtained for the base material and specimens with two hemispherical pits in transverse direction. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

18 pages, 5937 KiB

Open AccessArticle

Computational Fatigue Analysis of Auxetic Cellular Structures Made of SLM AlSi10Mg Alloy

by Miran Ulbin, Matej Borovinšek, Matej Vesenjak and Srečko Glodež

Metals 2020, 10(7), 945; https://doi.org/10.3390/met10070945 - 14 Jul 2020

Cited by 12 | Viewed by 3823

Abstract

In this study, a computational fatigue analysis of topology optimised auxetic cellular structures made of Selective Laser Melting (SLM) AlSi10Mg alloy is presented. Structures were selected from the Pareto front obtained by the multi-objective optimisation. Five structures with different negative Poisson’s ratios were [...] Read more.

In this study, a computational fatigue analysis of topology optimised auxetic cellular structures made of Selective Laser Melting (SLM) AlSi10Mg alloy is presented. Structures were selected from the Pareto front obtained by the multi-objective optimisation. Five structures with different negative Poisson’s ratios were considered for the parametric numerical analysis, where the fillet radius of cellular struts has been chosen as a parameter. The fatigue life of the analysed structures was determined by the strain–life approach using the Universal Slope method, where the needed material parameters were determined according to the experimental results obtained by quasi-static unidirectional tensile tests. The obtained computational results have shown that generally less auxetic structures tend to have a better fatigue life expectancy. Furthermore, the fillet radius has a significant impact on fatigue life. In general, the fatigue life decreases for smaller fillet radiuses (less than 0.3 mm) as a consequence of the high-stress concentrations, and also for larger fillet radiuses (more than 0.6 mm) due to the moving of the plastic zone away from the edge of the cell connections. The obtained computational results serve as a basis for further investigation, which should be focused on the experimental testing of the fabricated auxetic cellular structures made of SLM AlSi10Mg alloy under cyclic loading conditions. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

16 pages, 5464 KiB

Open AccessArticle

Ageing of Al-Mn-Cu-Be Alloys for Stimulating Precipitation of Icosahedral Quasicrystals

by Tonica Bončina, Mihaela Albu and Franc Zupanič

Metals 2020, 10(7), 937; https://doi.org/10.3390/met10070937 - 11 Jul 2020

Cited by 10 | Viewed by 2478

Abstract

In this work, the ageing of some Al-Mn-Cu-Be alloys was investigated in the temperature range in which predominantly icosahedral quasicrystalline (IQC) precipitates can form. The alloys were cast into a copper mould, directly aged (T5 heat treatment) between 300 and 440 °C for [...] Read more.

In this work, the ageing of some Al-Mn-Cu-Be alloys was investigated in the temperature range in which predominantly icosahedral quasicrystalline (IQC) precipitates can form. The alloys were cast into a copper mould, directly aged (T5 heat treatment) between 300 and 440 °C for different times. Afterwards, they were examined using scanning and transmission electron microscopy, X-ray diffraction and hardness testing. The main aim of the work was to determine the conditions at which a high number density of spherical icosahedral quasicrystalline precipitates can form. The highest number density of IQC precipitates was obtained at 300 °C after prolonged ageing. The spheroidal precipitates had a diameter less than 20 nm. The size of IQC precipitates increased with the increasing temperature, and in addition, decagonal quasicrystalline precipitates appeared. The time to maximum hardness decreased strongly with increasing ageing temperature. The IQC precipitates can form in a fairly broad temperature range in Al-Mn-Cu-Be alloys and that by varying ageing temperature and duration, rather different distributions of precipitates can be obtained. The presence of precipitates caused rather strong aluminium alloys and fast work hardening during initial plastic deformation. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

11 pages, 4680 KiB

Open AccessArticle

Correlations and Scalability of Mechanical Properties on the Micro, Meso and Macro Scale of Precipitation-Hardenable Aluminium Alloy EN AW-6082

by Anastasiya Toenjes, Heike Sonnenberg and Axel von Hehl

Metals 2020, 10(5), 608; https://doi.org/10.3390/met10050608 - 08 May 2020

Cited by 1 | Viewed by 2142

Abstract

The mechanical properties of heat-treatable aluminium alloys are improved and adjusted by three different heat treatment steps, which include solution annealing, quenching, and aging. Due to metal-physical correlations, variations in heat treatment temperatures and times lead to different microstructural conditions with differences in [...] Read more.

The mechanical properties of heat-treatable aluminium alloys are improved and adjusted by three different heat treatment steps, which include solution annealing, quenching, and aging. Due to metal-physical correlations, variations in heat treatment temperatures and times lead to different microstructural conditions with differences in the size and number of phases and their volume fraction in the microstructure. In this work, the investigations of the correlation between microhardness measurements on micro samples and the conventional mechanical properties (hardness, yield strength and tensile strength) of macro samples and the comparability of the different heat treatment states of micro and macro samples made of a hardenable aluminium alloy EN AW-6082 will be discussed. Using the correlations between the mechanical properties of micro samples and macro samples, the size of the samples and, thus, the testing cost and effort can be reduced. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

12 pages, 3564 KiB

Open AccessArticle

Effects of Homogenization Conditions on the Microstructure Evolution of Aluminium Alloy EN AW 8006

by Maja Vončina, Kristijan Kresnik, Darja Volšak and Jožef Medved

Metals 2020, 10(3), 419; https://doi.org/10.3390/met10030419 - 24 Mar 2020

Cited by 9 | Viewed by 3375

Abstract

The industrial production of products, such as foil and aluminium alloy strips, begins with the production of semi-finished products in the form of slabs. These are produced by the continuous casting process, which is quick and does not allow the equilibrium conditions of [...] Read more.

The industrial production of products, such as foil and aluminium alloy strips, begins with the production of semi-finished products in the form of slabs. These are produced by the continuous casting process, which is quick and does not allow the equilibrium conditions of solidification. Non-homogeneity—such as micro and macro segregation, non-equilibrium phases and microstructural constituents, as well as stresses arising during non-equilibrium solidification—are eliminated by means of homogenization annealing. In this way, a number of technological difficulties in the further processing of semi-finished products can be avoided. The aim of this research was the optimization of the homogenization annealing of the EN AW 8006 alloy. With the Thermo-Calc software, a thermodynamic simulation of equilibrium and non-equilibrium solidification was performed. Differential scanning calorimetry (DSC) was performed on selected samples in as-cast state and after various regimes of homogenization annealing and was used for the simulation of homogenization annealing. Using an optical microscope (OM), a scanning electron microscope (SEM) and an energy dispersion spectrometer (EDS), the microstructure of the samples was examined. Based on the results, it was concluded that homogenization annealing has already taken place after 8 h at 580 °C to the extent, that the material is then suitable for further processing. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

15 pages, 6516 KiB

Open AccessArticle

Research on Laser-TIG Hybrid Welding of 6061-T6 Aluminum Alloys Joint and Post Heat Treatment

by Hongyang Wang, Xiaohong Liu and Liming Liu

Metals 2020, 10(1), 130; https://doi.org/10.3390/met10010130 - 15 Jan 2020

Cited by 19 | Viewed by 6289

Abstract

The 6061-T6 aluminum (Al) alloys was joined by the laser induced tungsten inert gas (TIG) hybrid welding technique. It mainly studied the influences of welding parameters, solution, and aging (STA) treatment on the microstructure and tensile properties of Al alloy hybrid welding joints. [...] Read more.

The 6061-T6 aluminum (Al) alloys was joined by the laser induced tungsten inert gas (TIG) hybrid welding technique. It mainly studied the influences of welding parameters, solution, and aging (STA) treatment on the microstructure and tensile properties of Al alloy hybrid welding joints. Microstructures of the joints were also analyzed by optical microscopy and transmission electron microscopy. Results showed that the laser induced arc hybrid welding source changed the microstructure of the fusion zone and heat effect zone. STA treatment effectively improved the mechanical properties of the softening area in the hybrid welding joint, whose values of the tensile strength and elongation were on average 286 MPa and 20.5%. The distribution of the reinforcement phases and dislocations distributed were more uniform, which improved the property of STA treated joint. Full article

(This article belongs to the Special Issue Structure and Properties of Aluminium Alloys)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Structure and Properties of Aluminium Alloys

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (10 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI