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Microstructures and Mechanical Properties of Al Alloy

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 14239

Special Issue Editors

Department of Mechanical and Industrial Engineering (DIMI), University of Brescia, via Branze 38, 25123 Brescia, Italy
Interests: non-ferrous alloys; metallurgical characterization; foundry processes; mechanical properties; additive manufacturing; semisolid processing; rheology; heat treatments
Special Issues, Collections and Topics in MDPI journals
Department of Mechanical and Industrial Engineering (DIMI), University of Brescia, via Branze 38, 25123 Brescia, Italy
Interests: non-ferrous alloys; metallurgical characterization; foundry processes; mechanical properties; additive manufacturing; semisolid processing; rheology; heat treatments
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Nowadays, Al alloys are attracting more and more interest due to their peculiar properties, as such as high strength/weight ratio, good castability or formability, corrosion resistance, and so on. The applications of Al-based alloys are countless and their use is growing in various fields, from automotive and aircraft to packaging industries. According to the chemical composition of the alloy, the possible manufacturing processes are also various, ranging from foundry techniques to plastic deformation processes, together with additive manufacturing technologies. Therefore, the study of these alloys is fundamental in a constant effort towards exploiting their full potential.

The relationship between microstructural features and materials performance is a key issue in order to understand material behavior and to develop new alloys and novel new heat treatment routes.

The current Special Issue concerns the latest developments of Al alloys, with particular attention to the correlation between microstructure and mechanical performance. This is a key point in order to improve the engineering applications of these materials.

Microstructural studies based on characterization techniques, including various forms of microscopy (light, electron, etc.,) and analysis (microanalysis, X-ray diffraction, etc.), are welcome. The experimental investigation of mechanical properties, wear behavior, and/or corrosion resistance is of utmost interest, given that the influence of microstructure, processing history or application is described. The Guest Editors also encourage research papers reporting the influence of the manufacturing process on microstructural and mechanical features. Studies on innovative alloys and novel heat treatments are also welcome.

The aim is to publish papers that can represent an advance in the study of the correlations among the processing, properties, and performance of Al alloys.

Prof. Dr. Marcello Gelfi
Dr. Marialaura Tocci
Guest Editors

Manuscript Submission Information

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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. Materials is an international peer-reviewed open access semimonthly 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

  • Al alloys
  • microstuctural properties
  • microscopy
  • mechanical properties
  • mechanical testing
  • casting
  • plastic deformation
  • additive manufacturing
  • heat treatments
  • wear
  • corrosion

Published Papers (7 papers)

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Research

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11 pages, 3737 KiB  
Article
Effects of Zn Contents on Microstructure and Mechanical Properties of Semisolid Rheo-Diecasting Al-xZn-2Mg-1.5Cu Alloys
by Saiheng Hou, Jian Feng, Song Chen, Fan Zhang and Daquan Li
Materials 2022, 15(8), 2873; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15082873 - 14 Apr 2022
Viewed by 1439
Abstract
The microstructure and mechanical properties of semisolid rheo-diecasting Al-xZn-2Mg-1.5Cu alloys with different Zn contents were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness testing (HV) and room temperature tensile testing. Results show that the as-cast microstructure mainly consists of spherical α-Al [...] Read more.
The microstructure and mechanical properties of semisolid rheo-diecasting Al-xZn-2Mg-1.5Cu alloys with different Zn contents were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness testing (HV) and room temperature tensile testing. Results show that the as-cast microstructure mainly consists of spherical α-Al and Mg(Al, Cu, Zn)2 phases. Furthermore, a small amounts of Al7Cu2Fe phases were also detected along the grain boundary. Increasing the Zn contents from 8–12%, the volume fraction of the Mg(Al, Cu, Zn)2 phases increases from 4.9–7.4%. After solution heat treatment at 470 °C for 8 h, most of the Mg(Al, Cu, Zn)2 dissolves into the α-Al matrix, while the Al7Cu2Fe phase keeps with remains. The yield strength linearly increases from 482 ± 5 MPa of 8% Zn to 529 ± 5 MPa of 12% Zn. While, the ultimate strength of 10% Zn is 584 ± 2 MPa, which is higher than that of the other two alloys. Moreover, the average elongation dramatically decreases from 13% for the 8% Zn alloy to 2% for the 12% Zn alloy. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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15 pages, 11542 KiB  
Article
Research on Microstructure and Properties of AlSi10Mg Fabricated by Selective Laser Melting
by Wei Pan, Zhanggen Ye, Yongzhong Zhang, Yantao Liu, Bo Liang and Ziyu Zhai
Materials 2022, 15(7), 2528; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15072528 - 30 Mar 2022
Cited by 7 | Viewed by 1850
Abstract
In order to obtain high-performance aluminum alloy parts fabricated by selective laser melting, this paper investigates the relationship between the process parameters and microstructure properties of AlSi10Mg. The appropriate process parameters are obtained: the layer thickness is 0.03 mm, the laser power is [...] Read more.
In order to obtain high-performance aluminum alloy parts fabricated by selective laser melting, this paper investigates the relationship between the process parameters and microstructure properties of AlSi10Mg. The appropriate process parameters are obtained: the layer thickness is 0.03 mm, the laser power is 370 W, the scanning speed is 1454 mm/s, and the hatch spacing is 0.16 mm. With these process parameters, the ultimate tensile strength of the as-printed status is 500.7 ± 0.8 MPa, the yield strength is 311.5 ± 5.9 MPa, the elongation is 7.7 ± 0.5%, and the relative density is 99.94%. After annealing treatment at 275 °C for 2 h, the ultimate tensile strength is 310.8 ± 1.3 MPa, the yield strength is 198.0 ± 2.0 MPa, and the elongation is 13.7 ± 0.6%. The mechanical properties are mainly due to the high relative density, supersaturate solid solution, and fine dispersed Si. The supersaturate solid solution and nano-sized Si formed by the high cooling rate of SLM. After annealing treatment, the Si have been granulated and grown significantly. The ultimate tensile strength and yield strength are reduced, and the elongation is significantly improved. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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10 pages, 2110 KiB  
Article
Heat Treatments for Stress Relieving AlSi9Cu3 Alloy Produced by Laser Powder Bed Fusion
by Jacopo Fiocchi, Chiara Colombo, Laura Maria Vergani, Alberto Fabrizi, Giulio Timelli, Ausonio Tuissi and Carlo Alberto Biffi
Materials 2021, 14(15), 4184; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14154184 - 27 Jul 2021
Cited by 9 | Viewed by 1434
Abstract
The present work explores the effect of a stress relieving heat treatment on the microstructure, tensile properties and residual stresses of the laser powder bed fused AlSi9Cu3 alloy. In fact, the rapid cooling rates together with subsequent heating/cooling cycles occurred during layer by [...] Read more.
The present work explores the effect of a stress relieving heat treatment on the microstructure, tensile properties and residual stresses of the laser powder bed fused AlSi9Cu3 alloy. In fact, the rapid cooling rates together with subsequent heating/cooling cycles occurred during layer by layer additive manufacturing production make low temperature heat treatments desirable for promoting stress relaxation as well as limited grain growth: this combination can offer the opportunity of obtaining the best compromise between high strength, good elongation to failure and limited residual stresses. The microstructural features were analysed, revealing that the high cooling rate, induced by the process, caused a large supersaturation of the aluminum matrix and the refinement of the eutectic structure. Microhardness versus time curve, performed at 250 °C, allowed to identify a stabilization of the mechanical property at a duration of 25 h. The microstructure and the mechanical properties of the samples heat treated at 25 h and at 64 h, considered as a reference for the conventionally produced alloy, were compared with the ones of the as-built alloy. Finally, it was shown that a 59% reduction of the principal residual stresses could be achieved after the 25 h-long treatment and such evolution was correlated to the mechanical behaviour. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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10 pages, 3460 KiB  
Article
Alloying Elements Effects on Electrical Conductivity and Mechanical Properties of Newly Fabricated Al Based Alloys Produced by Conventional Casting Process
by Hany S. Abdo, Asiful H. Seikh, Jabair Ali Mohammed and Mahmoud S. Soliman
Materials 2021, 14(14), 3971; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14143971 - 16 Jul 2021
Cited by 26 | Viewed by 2874
Abstract
The present investigation deals with a comprehensive study on the production of aluminum based alloys with the incorporation of different alloying elements and their effect on its electrical conductivity and mechanical properties. Casting of pure aluminum with different concentration and combinations of alloying [...] Read more.
The present investigation deals with a comprehensive study on the production of aluminum based alloys with the incorporation of different alloying elements and their effect on its electrical conductivity and mechanical properties. Casting of pure aluminum with different concentration and combinations of alloying additives such as cupper (Cu), magnesium (Mg) and silver (Ag) were carried out using a graphite crucible. The as-cast microstructure was modified by hot rolling followed by different heat-treated conditions viz., annealing, normalizing, quenching, and age hardening. The mechanical properties and electrical conductivity of the produced heat-treated alloys sheets under various processing conditions were carried out using tensile testing, hardness, and electrical resistivity measurements. It was found that by increasing the alloying elements content, yield strength results increased significantly by more than 250% and 500% for the as rolled and 8 h aged Al-Cu-Mg alloy, respectively. On the other hand, the electrical conductivity reduces slightly with −14.6% and −16.57% for the as rolled and 8 h aged of the same Al-Cu-Mg alloy, respectively. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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15 pages, 40313 KiB  
Article
Effect of Returnable Material in Batch on Hot Tearing Tendency of AlSi9Cu3 Alloy
by Justyna Kasińska, Marek Matejka, Dana Bolibruchová, Michal Kuriš and Lukáš Širanec
Materials 2021, 14(7), 1583; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14071583 - 24 Mar 2021
Cited by 1 | Viewed by 1548
Abstract
The main reason for the use of returnable material, or recycled alloys, is a cost reduction while maintaining the final properties of the casting. The casting resulting quality is directly related to the correct ratio of commercial grade alloy and alloy made by [...] Read more.
The main reason for the use of returnable material, or recycled alloys, is a cost reduction while maintaining the final properties of the casting. The casting resulting quality is directly related to the correct ratio of commercial grade alloy and alloy made by remelting the returnable material in the batch. The casting quality is also affected by the purity of the secondary raw materials used, the shape complexity and the use of the casting itself. The presented article focuses on the effect of increasing the returnable material content in the batch on the hot tearing susceptibility of AlSi9Cu3 alloy. Hot tears are a complex phenomenon that combines metallurgical and thermo-mechanical interactions of the cast metal. Hot tearing susceptibility was evaluated on the basis of quantitative (HTS—hot tearing susceptibility index) and qualitative evaluation. The negative effect of returnable material in the batch was already manifested at a 20% content in the batch. The critical proportion of the returnable alloy in the batch can be stated as 50%. The alloy with a 50% returnable material content manifested insufficient results of the HTS index and qualitative evaluation, which means increased sensitivity to tearing. The negative effect of returnable material and the increased sensitivity were also confirmed in the evaluation of the fracture surface and hot tear profile. The microstructure of alloys with 50% and higher proportion of returnable material was characterized by a higher amount of iron phases (mainly Al5FeSi), whose sharp ends acted as critical regions of hot tearing and subsequent hot tear propagation, which had a major impact on the increase in hot tearing susceptibility. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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12 pages, 4333 KiB  
Article
Effect of Zr Microalloying on the Microstructures and Strengthening Mechanism of As-Cast Al-Fe-Zr Alloys
by Jieyun Ye, Renguo Guan, Hongjin Zhao, Changwei He and Kezhi Xiong
Materials 2020, 13(21), 4744; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13214744 - 23 Oct 2020
Cited by 2 | Viewed by 1691
Abstract
The microstructure and mechanical properties of Al-0.35Fe alloys with a series of different zirconium (Zr) additions from 0.1 to 0.4% are investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile testing. The as-cast structure of the alloys varies with the [...] Read more.
The microstructure and mechanical properties of Al-0.35Fe alloys with a series of different zirconium (Zr) additions from 0.1 to 0.4% are investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile testing. The as-cast structure of the alloys varies with the Zr content. When the content of Zr is 0.1%, Zr dissolves into the aluminum (Al) matrix completely and iron (Fe) concentrates along the boundary in a network of eutectic Al3Fe. With the increase in Zr content to 0.2% and above, nanoscale Al3Zr particles appear in the alloy. With the Zr content increasing from 0.1 to 0.4%, the grain size of the Al matrix decreases from 73 to 23 μm. The morphology of the eutectic Al3Fe phase changes from short rod-like to an agglomerated structure consisting of finer and shorter rod-like shapes. The tensile and yield strengths increase while the total elongation decreases with increasing Zr content. The strengthening mechanism of the alloy can be attributed to the combination of fine-grain, solution and second-phase strengthening. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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Review

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19 pages, 7874 KiB  
Review
A Personal View of Microstructure and Properties of Al Alloys
by John Campbell
Materials 2021, 14(5), 1297; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14051297 - 08 Mar 2021
Cited by 8 | Viewed by 2074
Abstract
This paper presents a personal view by the author of the role of bifilms in Al alloys. The mantra ‘microstructure determines properties’ is widely accepted as a truism, but is here critically assessed and found wanting. The case is made that bifilms from [...] Read more.
This paper presents a personal view by the author of the role of bifilms in Al alloys. The mantra ‘microstructure determines properties’ is widely accepted as a truism, but is here critically assessed and found wanting. The case is made that bifilms from the casting process, while often invisible in the microstructure, are usually at least as important, if not of far greater importance, because they are often present as a dense population of cracks throughout the metal. The bifilm population controls the morphology of many features of cast and wrought structures. For cast alloys, bifilm control of pore morphology and Si morphology in Al–Si alloys is discussed, as is dendrite arm spacing (DAS). The tensile property benefits of grain refinement are seen to be mainly bifilm controlled. The properties ductility and fatigue appear to be especially dominated by bifilm content, as are invasive corrosion processes such as pitting, intergranular corrosion, hydrogen blistering and cracking. Bifilm control is proposed as a new concept permitting the improvement and control of metallurgical properties. Full article
(This article belongs to the Special Issue Microstructures and Mechanical Properties of Al Alloy)
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