Editorial

2 pages, 155 KiB

Open AccessEditorial

Mechanical Performance and Microstructural Characterization of Light Alloys

by Qinghuan Huo

Materials 2023, 16(17), 5915; https://doi.org/10.3390/ma16175915 - 29 Aug 2023

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The present Special Issue titled “Mechanical Performance and Microstructural Characterization of Light Alloys” aims to report the close relation between mechanical performance and microstructure in light alloys, such as Al, Mg, Ti, and their alloys [...] Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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11 pages, 6874 KiB

Open AccessArticle

Enhanced Anti-Corrosion Performance of Co-Cr-Mo Alloy in Molten Al by Prior Oxidation Treatment

by Rongrong Shang, Biaobiao Yang and Yunping Li

Materials 2023, 16(23), 7449; https://doi.org/10.3390/ma16237449 - 30 Nov 2023

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Abstract

Co-based alloys are promising alternatives to replace the currently used tool steels in aluminum die-casting molds for producing sophisticated products. Although the reaction is significantly less severe compared to that of tool steels, bare Co-29Cr-6Mo (CCM) alloy is still gradually corroded under molten [...] Read more.

Co-based alloys are promising alternatives to replace the currently used tool steels in aluminum die-casting molds for producing sophisticated products. Although the reaction is significantly less severe compared to that of tool steels, bare Co-29Cr-6Mo (CCM) alloy is still gradually corroded under molten Al, leading to the local failure of the alloy due to the formation of intermetallic compounds between the matrix and molten Al. This study indicated that prior oxidation treatment at 750 °C on CCM alloy is beneficial in enhancing the corrosion resistance of the alloy to molten Al. The is more pronounced in the alloy after a longer oxidation treatment. However, after oxidation for longer than 24 h, the protectiveness of the film cannot be enhanced anymore. In addition, even after the full failure of the oxide film, the thickness loss rate of a sample with prior oxidation treatment is much lower than that of a bare sample. This can be attributed to the fact that network-aligned oxide particles of the cone structure boundary inhibit both the outwards movements of alloying elements and the dissolution of the intermetallic layer. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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14 pages, 4501 KiB

Open AccessArticle

Shaping the Structure and Properties of TiO₂-ZnO Oxide Coatings Produced by Plasma Electrolytic Oxidation on Titanium Substrate

by Magdalena Marny, Maciej Sowa, Alicja Kazek-Kęsik, Krzysztof Rokosz, Steinar Raaen, Patrick Chapon, Roman Viter, Roman Pshenychnyi, Wojciech Simka and Joanna Michalska

Materials 2023, 16(23), 7400; https://doi.org/10.3390/ma16237400 - 28 Nov 2023

Cited by 1 | Viewed by 665

Abstract

The paper presents the results of preliminary research on the possibility of synthesizing ZnO-TiO₂ mixed coatings by plasma electrochemical oxidation (PEO). The aim of the work was to synthesize TiO₂-ZnO mixed coatings on a titanium substrate from an electrolyte containing [...] Read more.

The paper presents the results of preliminary research on the possibility of synthesizing ZnO-TiO₂ mixed coatings by plasma electrochemical oxidation (PEO). The aim of the work was to synthesize TiO₂-ZnO mixed coatings on a titanium substrate from an electrolyte containing ZnO nanoparticles (NPs) and to assess the parameters of PEO on the structure, chemical composition, and properties of the obtained oxide coatings. The PEO process was carried out under various current–voltage conditions using different signals: DC, DC pulse, and AC. In this work, optimal conditions for the PEO process were determined to obtain well-adhering oxide coatings with the highest possible content of ZnO. The structure and morphology of the resulting oxide coatings were investigated, and their chemical and phase composition was comprehensively examined (EDX, XRD, XPS, and GD-OES). In addition, their basic optical properties were assessed. It has been shown that in the PEO DC pulse process, it is possible to obtain oxide coatings characterized by a high degree of structure order, high ZnO content in the oxide coating (3.6 at.%, XPS), and prospective applications for photocatalytic purposes (3.12 eV). Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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16 pages, 6222 KiB

Open AccessArticle

Aluminum Foam Sandwich: Pore Evolution Mechanism Investigation and Engineering Preparing Optimization

by Xi Sun, Zhiqian Jian, Xixi Su, Peng Huang, Qiang Gao, Zhanhao Feng and Guoyin Zu

Materials 2023, 16(19), 6479; https://doi.org/10.3390/ma16196479 - 29 Sep 2023

Cited by 2 | Viewed by 627

Abstract

This paper employs an innovative investigation approach to study pore evolution in Al-Si-Mg-Cu alloy within aluminum foam sandwiches (AFS) by integrating data from heating–expansion ratio curves, in situ observation of synchronous radiation, and microscopic analysis of the matrix’s microstructure at different stages. Additionally, [...] Read more.

This paper employs an innovative investigation approach to study pore evolution in Al-Si-Mg-Cu alloy within aluminum foam sandwiches (AFS) by integrating data from heating–expansion ratio curves, in situ observation of synchronous radiation, and microscopic analysis of the matrix’s microstructure at different stages. Additionally, the cavity design and plate type control for large-scale AFS production are explored. Findings categorize the precursor heating into three stages: rapid heating, solid–liquid transition, and stable foaming. During solid–liquid transition, the expansion rate experiences a sudden drop, associated with pore nucleation and edge cracking of precursors. Pores nucleate as elongated crack-like structures along the rolling direction, guided by the Mg-enriched regions. In stable foaming, these pores evolve, become spherical, and the matrix rapidly expands. Using square tubes for sealing on the preform cavity sides creates a dense edge zone during rolling, halting crack propagation into the powder core. Adopting edge sealing during foaming mitigates boundary effects, thereby improving AFS panel flatness. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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13 pages, 6112 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Al and Ti Additions on Solid Solution Strengthening and Precipitation Hardening in CoNiFe Medium-Entropy Alloys

by Piotr Bała, Kamil Górecki, Rafał Dziurka and Tomasz Kozieł

Materials 2023, 16(18), 6297; https://doi.org/10.3390/ma16186297 - 20 Sep 2023

Cited by 2 | Viewed by 1050

Abstract

The effect of Al and Ti additions on the microstructure and properties of CoNiFe alloys was studied in this paper. The investigations were conducted on four specially designed and produced arc furnace alloys (from 3 to 5 components, with medium to high entropy). [...] Read more.

The effect of Al and Ti additions on the microstructure and properties of CoNiFe alloys was studied in this paper. The investigations were conducted on four specially designed and produced arc furnace alloys (from 3 to 5 components, with medium to high entropy). Samples in various states were analyzed, i.e., as-cast, after homogenization, after solution heat treatment, and after solution heat treatment and aging. The obtained samples were characterized by: SEM observations, EDS, XRD, TEM analyses, and finally, hardness measurements. The solid solution strengthening coming from the addition of 5 at. pct. Al was negligible, while the effect from the 5 at. pct. of Ti addition was significant. The precipitation hardening effect related to the presence of the (CoNi)₃Ti phase caused by the Ti addition is comparable with the total effect of the Al and Ti addition, which caused the precipitation of (NiCo)₃AlTi. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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16 pages, 10959 KiB

Open AccessArticle

Dependence of Tensile Properties and Fracture Behaviors on the Fractions of Continuous and Discontinuous Precipitates in Peak-Aged AZ80A Magnesium Alloy

by Kelong Zhang, Huizhong Li, Xiaopeng Liang, Zhi Chen, Hui Tao, Yixuan Che, Li Li, Zixiang Luo and Qinghuan Huo

Materials 2023, 16(13), 4546; https://doi.org/10.3390/ma16134546 - 23 Jun 2023

Cited by 1 | Viewed by 841

Abstract

After T5 (forging + aging) and different T6 (forging + solution + aging) heat treatments, the AZ80A Mg alloys exhibited microstructures with different fractions of continuous precipitate (CP) regions and discontinuous precipitate (DP) regions. The effects of the fractions of DP regions and [...] Read more.

After T5 (forging + aging) and different T6 (forging + solution + aging) heat treatments, the AZ80A Mg alloys exhibited microstructures with different fractions of continuous precipitate (CP) regions and discontinuous precipitate (DP) regions. The effects of the fractions of DP regions and CP regions on the tensile properties and fracture behaviors were investigated using microstructural characterizations and analysis. The results showed that increasing the fraction of DP regions enhanced the yield strength and tensile strength at room temperature. However, at the same high temperature, increasing the fractions of DP regions improved the elongation but deteriorated the tensile strength significantly. The different resultant tensile properties at different temperatures were caused by the different precipitation-strengthening effects in the CP and DP regions. The strengthening contribution of the DP regions was more effective at room temperature but became inferior to the effect brought about by the CP regions at high temperatures. Micro-cracks were usually initiated and propagated in the CP regions at room temperature. At high temperatures, however, micro-voids formed more easily in the DP regions, and the fracture path preferred to locate there. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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23 pages, 11745 KiB

Open AccessArticle

Uncovering Dislocation- and Precipitate-Induced Viscoplastic Damage in Al-Zn-Mg Alloy

by Yunlong Zheng, Ning Guo, Bingtao Tang, Baoyi Su and Qingjun Zhou

Materials 2023, 16(10), 3769; https://doi.org/10.3390/ma16103769 - 16 May 2023

Cited by 2 | Viewed by 898

Abstract

The existing phenomenological theories of plastic forming of sheet metal lack the predictability of the influences of dislocations and precipitates on viscoplastic damage in Al-Zn-Mg alloys. This study examines the evolution of grain size that occurs when the Al-Zn-Mg alloy undergoes a hot [...] Read more.

The existing phenomenological theories of plastic forming of sheet metal lack the predictability of the influences of dislocations and precipitates on viscoplastic damage in Al-Zn-Mg alloys. This study examines the evolution of grain size that occurs when the Al-Zn-Mg alloy undergoes a hot deformation process, specifically concentrating on dynamic recrystallization (DRX). The uniaxial tensile tests are conducted at deformation temperatures ranging from 350 to 450 °C and strain rates of 0.01–1 s⁻¹. The intragranular and intergranular dislocation configurations and their interactions with dynamic precipitates are revealed by transmission electron microscopy (TEM). In addition, the MgZn₂ phase induces microvoid formation. Subsequently, an improved multiscale viscoplastic constitutive model is established that emphasizes the effect of precipitates and dislocations on the evolution of microvoid-based damage. Using a calibrated and validated micromechanical model, the simulation of hot-formed U-shaped parts is conducted through finite element (FE) analysis. During the hot U-forming process, the formation of defects is expected to have an impact on both the distribution of thickness and the level of damage. In particular, the damage accumulation rate is influenced by temperature and strain rate, and local thinning is caused by the damage evolution of U-shaped parts. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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18 pages, 10589 KiB

Open AccessArticle

Synthesis and Characterization of Al Chip-Based Syntactic Foam Containing Glass Hollow Spheres Fabricated by a Semi-Solid Process

by Yong-Guk Son and Yong-Ho Park

Materials 2023, 16(6), 2304; https://doi.org/10.3390/ma16062304 - 13 Mar 2023

Cited by 1 | Viewed by 932

Abstract

In this study, aluminum (Al) chip matrix-based synthetic foams were fabricated by hot pressing at a semi-solid (SS) temperature. The densities of the foams ranged from 2.3 to 2.63 g/cm³, confirming that the density decreased with increasing glass hollow sphere (GHS) [...] Read more.

In this study, aluminum (Al) chip matrix-based synthetic foams were fabricated by hot pressing at a semi-solid (SS) temperature. The densities of the foams ranged from 2.3 to 2.63 g/cm³, confirming that the density decreased with increasing glass hollow sphere (GHS) content. These values were approximately 16% lower than the densities of Al chip alloys without GHS. The Al chip syntactic foam microstructure fabricated by the semi-solid process comprised GHS uniformly distributed around the Al chip matrix and a spherical microstructure surrounded by the Mg₂Si phase in the interior. The resulting spherical microstructure contributed significantly to the improvement of mechanical properties. Mechanical characterization confirmed that the Al chip syntactic foam exhibited a compressive strength of approximately 225–288 MPa and an energy absorption capacity of 46–47 MJ/M³. These results indicate higher compressive properties than typical Al syntactic foam. The Al chip microstructure, consisting of the Mg₂Si phase and GHS, acted as a load-bearing element during compression, significantly contributing to the compressive properties of the foam. An analysis was performed using an energy-dispersive spectrometer to validate the interfacial reaction between the GHS and the matrix. The results showed that MgAl₂O₄ was uniformly coated around GHS, which contributed not only to the strength of the matrix, but also to the mechanical properties via the appropriate interfacial reactive coating. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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13 pages, 6146 KiB

Open AccessArticle

Thermal Stability and Mechanical Behavior of Ultrafine-Grained Titanium with Different Impurity Content

by Kamil Majchrowicz, Agata Sotniczuk, Joanna Malicka, Emilia Choińska and Halina Garbacz

Materials 2023, 16(4), 1339; https://doi.org/10.3390/ma16041339 - 04 Feb 2023

Cited by 7 | Viewed by 1446

Abstract

Ultrafine-grained (UFG) commercially pure (Ti Grade 2) and high-purity (Ti 99.99%) titanium can be a good alternative to less biocompatible Ti alloys in many biomedical applications. Their severe plastic deformation may lead to a substantial increase of strength, but their highly refined microstructure [...] Read more.

Ultrafine-grained (UFG) commercially pure (Ti Grade 2) and high-purity (Ti 99.99%) titanium can be a good alternative to less biocompatible Ti alloys in many biomedical applications. Their severe plastic deformation may lead to a substantial increase of strength, but their highly refined microstructure show a lower thermal stability which may limit their range of applications. The purpose of this study was to investigate the effect of interstitial elements on the thermal stability of UFG Ti Grade 2 and high-purity Ti 99.99% processed by a multi-pass cold rolling to the total thickness reduction of 90%. The severely cold rolled Ti sheets were annealed at temperature in the range of 100–600 °C for 1 h and, subsequently, they were evaluated in terms of microstructure stability, mechanical performance as well as heat effects measured by differential scanning calorimetry (DSC). It was found that the microstructure and mechanical properties were relatively stable up to 200 and 400 °C in the case of UFG Ti 99.99% and Ti Grade 2, respectively. DSC measurements confirmed the aforementioned results about lower temperature of recovery and recrystallization processes in the high-purity titanium. Surprisingly, the discontinuous yielding phenomenon occurred in both investigated materials after annealing above their thermal stability range, which was further discussed based on their microstructural characteristics. Additionally, the so-called hardening by annealing effect was observed within their thermal stability range (i.e., at 100–400 °C for UFG Ti Grade 2 and 100 °C for UFG Ti 99.99%). Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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15 pages, 6877 KiB

Open AccessArticle

Hardness Distribution of Al2050 Parts Fabricated Using Additive Friction Stir Deposition

by Hamed Ghadimi, Huan Ding, Selami Emanet, Mojtaba Talachian, Chase Cox, Michael Eller and Shengmin Guo

Materials 2023, 16(3), 1278; https://doi.org/10.3390/ma16031278 - 02 Feb 2023

Cited by 7 | Viewed by 2133

Abstract

The solid-state additive friction stir deposition (AFSD) process is a layer-by-layer metal 3D-printing technology. In this study, AFSD is used to fabricate Al–Cu–Li 2050 alloy parts. The hardness values for various regions of the as-deposited built parts are measured, and the results are [...] Read more.

The solid-state additive friction stir deposition (AFSD) process is a layer-by-layer metal 3D-printing technology. In this study, AFSD is used to fabricate Al–Cu–Li 2050 alloy parts. The hardness values for various regions of the as-deposited built parts are measured, and the results are contrasted with those of the feedstock material. The as-fabricated Al2050 parts are found to have a unique hardness distribution due to the location-specific variations in the processing temperature profile. The XRD results indicate the presence of the secondary phases in the deposited parts, and EDS mapping confirms the formation of detectable alloying particles in the as-deposited Al2050 matrix. The AFSD thermal–mechanical process causes the unique hardness distribution and the reduced microhardness level in the AFSD components, in contrast to those of the feedstock material. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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18 pages, 13690 KiB

Open AccessArticle

Microstructure Evolution, Constitutive Modelling, and Superplastic Forming of Experimental 6XXX-Type Alloys Processed with Different Thermomechanical Treatments

by Andrey G. Mochugovskiy, Ahmed O. Mosleh, Anton D. Kotov, Andrey V. Khokhlov, Ludmila Yu. Kaplanskaya and Anastasia V. Mikhaylovskaya

Materials 2023, 16(1), 445; https://doi.org/10.3390/ma16010445 - 03 Jan 2023

Cited by 7 | Viewed by 1815

Abstract

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the [...] Read more.

This study focused on the microstructural analysis, superplasticity, modeling of superplastic deformation behavior, and superplastic forming tests of the Al-Mg-Si-Cu-based alloy modified with Fe, Ni, Sc, and Zr. The effect of the thermomechanical treatment with various proportions of hot/cold rolling degrees on the secondary particle distribution and deformation behavior was studied. The increase in hot rolling degree increased the homogeneity of the particle distribution in the aluminum-based solid solution that improved superplastic properties, providing an elongation of ~470–500% at increased strain rates of (0.5–1) × 10⁻² s⁻¹. A constitutive model based on Arrhenius and Beckofen equations was used to describe and predict the superplastic flow behavior of the alloy studied. Model complex-shaped parts were processed by superplastic forming at two strain rates. The proposed strain rate of 1 × 10⁻² s⁻¹ provided a low thickness variation and a high quality of the experimental parts. The residual cavitation after superplastic forming was also large at the low strain rate of 2 × 10⁻³ s⁻¹ and significantly smaller at 1 × 10⁻² s⁻¹. Coarse Al₉FeNi particles did not stimulate the cavitation process and were effective to provide the superplasticity of alloys studied at high strain rates, whereas cavities were predominately observed near coarse Mg₂Si particles, which act as nucleation places for cavities during superplastic deformation and forming. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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12 pages, 7057 KiB

Open AccessArticle

Tailoring of Dissimilar Friction Stir Lap Welding of Aluminum and Titanium

by Alexander Kalinenko, Pavel Dolzhenko, Yulia Borisova, Sergey Malopheyev, Sergey Mironov and Rustam Kaibyshev

Materials 2022, 15(23), 8418; https://doi.org/10.3390/ma15238418 - 26 Nov 2022

Cited by 5 | Viewed by 1288

Abstract

An approach was proposed to optimize dissimilar friction stir lap welding of aluminum and titanium alloys. The basic concept of the new technique included (i) the plunging of the welding tool solely into the aluminum part (i.e., no direct contact with the titanium [...] Read more.

An approach was proposed to optimize dissimilar friction stir lap welding of aluminum and titanium alloys. The basic concept of the new technique included (i) the plunging of the welding tool solely into the aluminum part (i.e., no direct contact with the titanium side) and (ii) the welding at a relatively high-heat input condition. It was shown that sound welds could be readily produced using an ordinary cost-effective tool, with no tool abrasion and no dispersion of harmful titanium fragments within the aluminum side. Moreover, the intermetallic layer was found to be as narrow as ~0.1 µm, thus giving rise to excellent bond strength between aluminum and titanium. On the other hand, several important shortcomings were also revealed. First of all, the high-heat input condition provided significant microstructural changes in the aluminum part, thereby resulting in essential material softening. Furthermore, the new approach was not feasible in the case of highly alloyed aluminum alloys due to the relatively low rate of self-diffusion in these materials. An essential issue was also a comparatively narrow processing window. Full article

(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys)

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