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Microstructure Engineering of Metals and Alloys, Volume II

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: 20 May 2024 | Viewed by 7362

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Prof. Dr. Konstantin Borodianskiy

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Guest Editor

Department of Chemical Engineering, Ariel University, Ariel 40700, Israel
Interests: functional and bioactive coatings; microstructural engineering; materials for solid oxide fuel cells; metallurgy; Al alloys; metallic properties
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Special Issue Information

Dear Colleagues,

After our successful first volume of the Special Issue “Microstructure Engineering of Metals and Alloys”, we decided to make the special issue as a collection on this topic. Metals and alloys are materials that combine high mechanical properties such as strength, ductility, and stiffness with high physical properties such as electrical and thermal conductivity. These materials are generally split into ferrous (steels and cast irons) and non-ferrous alloys (aluminum, magnesium, titanium, copper, nickel, zinc, and others).

Both materials’ structures are formed of one, two, or more phases, and structural defects (vacancies, dislocations, grain boundaries, and others) affect their properties. Therefore, microstructure engineering is an effective approach to achieve the desired performance of metals and alloys. Moreover, this topic attracts researchers all around the globe who focus on different aspects of structure formation, including processing, alloying, and tailoring of a production condition.

Metallic microstructure observation is commonly carried out using an optical microscope. However, from the middle of the 20th century, electron microscopy (EM) became a more effective structural evaluation method. Microstructure characterization with EM makes a “deep view” into the metal available. Thus, recent progress in understanding the structural formation of some metals may be referred to as the development and implementation of electron microscopy. However, this tool is not exclusive; other available techniques are also valuable in understanding the metallic structure. Thus, X-ray and electron diffraction analysis is responsible for phase detection, and electron backscatter diffraction provides crystallographic information.

The scope of the Special Issue will focus on recent innovations in the microstructure engineering of metals and alloys. Topics include, but are not limited to:

Ferrous and non-ferrous alloys
Metals fabrication
Alloying and modification
Microstructural evaluation
Optical and electron microscopy
Coatings and surfaces
Metal joining processes
Modeling and simulation of metallic materials

I invite you to submit a manuscript, which can be a full paper, communication, or a review of this Special Issue.

Prof. Dr. Konstantin Borodianskiy
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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

microstructural evaluation
metals and alloys
phase composition
optical and electron microscopy
coatings and surfaces
mechanical, chemical, and physical properties
metal fabrication processes
modification and alloying processes
welding, brazing, soldering and other joining process in metals
modeling and simulation of metallic materials

Published Papers (10 papers)

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Research

24 pages, 10404 KiB

Open AccessArticle

Microstructure Evolution and Fretting Wear Mechanisms of Steels Undergoing Oscillatory Sliding Contact in Dry Atmosphere

by Alyssa A. Maich, Ronald Gronsky and Kyriakos Komvopoulos

Materials 2024, 17(8), 1737; https://doi.org/10.3390/ma17081737 - 10 Apr 2024

Viewed by 369

Abstract

Variations in the microstructure and the dominant fretting wear mechanisms of carbon steel alloy in oscillatory sliding contact against stainless steel in a dry atmosphere were evaluated by various mechanical testing and microanalytical methods. These included scanning electron microscopy and energy dispersive spectrometry with corresponding elemental maps of the wear tracks, in conjunction with cross-sectional transmission electron microscopy of samples prepared by focused ion beam machining to assess subsurface and through-thickness changes in microstructure, all as a function of applied load and sliding time. Heavily dislocated layered microstructures were observed below the wear tracks to vary with both the load and sliding time. During the accumulation of fretting cycles, the subsurface microstructure evolved into stable dislocation cells with cell walls aligned parallel to the surface and the sliding direction. The thickness of the damaged subsurface region increased with the load, consistent with the depth distribution of the maximum shear stress. The primary surface oxide evolved as Fe₂O₃ and Fe₃O₄ with increasing sliding time, leading to the formation of a uniform oxide scale at the sliding surface. It is possible that the development of the dislocation cell structure in the subsurface also enhanced oxidation by pipe diffusion along dislocation cores. The results of this study reveal complex phase changes affecting the wear resistance of steels undergoing fretting wear, which involve a synergy between oxidative wear, crack initiation, and crack growth along dislocation cell walls due to the high strains accumulating under high loads and/or prolonged surface sliding. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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12 pages, 4863 KiB

Open AccessArticle

Effect of Zinc and Severe Plastic Deformation on Mechanical Properties of AZ61 Magnesium Alloy

by Song-Jeng Huang, Sheng-Yu Wu and Murugan Subramani

Materials 2024, 17(7), 1678; https://doi.org/10.3390/ma17071678 - 05 Apr 2024

Viewed by 556

Abstract

This study investigates the effects of zinc (4 wt.%) and severe plastic deformation on the mechanical properties of AZ61 magnesium alloy through the stir-casting process. Severe plastic deformation (Equal Channel Angular Pressing (ECAP)) has been performed followed by T4 heat treatment. The microstructural examinations revealed that the addition of 4 wt.% Zn enhances the uniform distribution of β-phase, contributing to a more uniformly corroded surface in corrosive environments. Additionally, dynamic recrystallization (DRX) significantly reduces the grain size of as-cast alloys after undergoing ECAP. The attained mechanical properties demonstrate that after a single ECAP pass, AZ61 + 4 wt.% Zn alloy exhibits the highest yield strength (YS), ultimate compression strength (UCS), and hardness. This research highlights the promising potential of AZ61 + 4 wt.% Zn alloy for enhanced mechanical and corrosion-resistant properties, offering valuable insights for applications in diverse engineering fields. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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15 pages, 6948 KiB

Open AccessArticle

Enhancement of Strength–Ductility Synergy of Al-Li Cast Alloy via New Forming Processes and Sc Addition

by Shulin Lü, Zhaoxiang Yan, Yu Pan, Jianyu Li, Shusen Wu and Wei Guo

Materials 2024, 17(7), 1558; https://doi.org/10.3390/ma17071558 - 28 Mar 2024

Viewed by 516

Abstract

In this study, concurrent enhancements in both strength and ductility of the Al-2Li-2Cu-0.5Mg-0.2Zr cast alloy (hereafter referred to as Al-Li) were achieved through an optimized forming process comprising ultrasonic treatment followed by squeeze casting, coupled with the incorporation of Sc. Initially, the variations in the microstructure and mechanical properties of the Sc-free Al-Li cast alloy (i.e., alloy A) during various forming processes were investigated. The results revealed that the grain size in the UT+SC (ultrasonic treatment + squeeze casting) alloy was reduced by 76.3% and 57.7%, respectively, compared to those of the GC (gravity casting) or SC alloys. Additionally, significant improvements were observed in its compositional segregation and porosity reduction. After UT+SC, the ultimate tensile strength (UTS), yield strength (YS), and elongation reached 235 MPa, 135 MPa, and 15%, respectively, which were 113.6%, 28.6%, and 1150% higher than those of the GC alloy. Subsequently, the Al-Li cast alloy containing 0.2 wt.% Sc (referred to as alloy B) exhibited even finer grains under the UT+SC process, resulting in simultaneous enhancements in its UTS, YS, and elongation. Interestingly, the product of ultimate tensile strength and elongation (i.e., UTS × EL) for both alloys reached 36 GPa•% and 42 GPa•%, respectively, which is much higher than that of other Al-Li cast alloys reported in the available literature. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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14 pages, 5614 KiB

Open AccessArticle

Preparation and Performance of Micro-Arc Oxidation Coatings for Corrosion Protection of LaFe_11.6Si_1.4 Alloy

by Ruzhao Chen, Bin Fu, Jie Han, Hu Zhang, Ping Wang and Hongxia Yin

Materials 2024, 17(6), 1316; https://doi.org/10.3390/ma17061316 - 13 Mar 2024

Viewed by 427

Abstract

The microstructure, corrosion resistance, and phase-transition process of micro-arc oxidation (MAO) coatings prepared on LaFe_11.6Si_1.4 alloy surfaces in different electrolyte systems were systematically investigated. Research has demonstrated that various electrolyte systems do not alter the main components of the coatings. However, the synergistic action of Na₂CO₃ and Na₂B₄O₇ more effectively modulated the ionization and chemical reactions of the MAO process and accelerated the formation of α-Al₂O₃. Moreover, the addition of Na₂CO₃ and Na₂B₄O₇ improved the micromorphology of the coating, resulting in a uniform coating thickness and good bonding with the LaFe_11.6Si_1.4 substrate. The dynamic potential polarization analysis was performed in a three-electrode system consisting of a LaFe_11.6Si_1.4 working electrode, a saturated calomel reference electrode, and a platinum auxiliary electrode. The results showed that the self-corrosion potential of the LaFe_11.6Si_1.4 alloy without surface treatment was −0.68 V, with a current density of 8.96 × 10⁻⁶ A/cm². In contrast, the presence of a micro-arc electrolytic oxidation coating significantly improved the corrosion resistance of the LaFe_11.6Si_1.4 substrate, where the minimum corrosion current density was 1.32 × 10⁻⁷ A/cm² and the corrosion potential was −0.50 V. Similarly, after optimizing the MAO electrolyte with Na₂CO₃ and Na₂B₄O₇, the corrosion resistance of the material further improved. Simultaneously, the effect of the coatings on the order of the phase transition, latent heat, and temperature is negligible. Therefore, micro-arc oxidation technology based on the in situ growth coating of the material surface effectively improves the working life and stability of La(Fe, Si)₁₃ materials in the refrigeration cycle, which is an excellent alternative as a protection technology to promote the practical process of magnetic refrigeration technology. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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8 pages, 4554 KiB

Open AccessCommunication

The Tunable Rhenium Effect on the Creep Properties of a Nickel-Based Superalloy

by Xiao-Zhi Tang and Ya-Fang Guo

Materials 2024, 17(1), 191; https://doi.org/10.3390/ma17010191 - 29 Dec 2023

Viewed by 503

Abstract

Atomistic simulations on the creep of a nickel-based single-crystal superalloy are performed for examining whether the so-called rhenium effect can be tuned by changing the spatial distribution of rhenium in the nickel matrix phase. Results show that Rhenium dopants at {100} phase interfaces facilitate mobile partial dislocations, which intensify the creep, leading to a larger creep strain than that of a pure Ni/Ni3Al system containing no alloying dopants. If all the Re dopants in the matrix phase are far away from phase interfaces, a conventional retarding effect of Re can be observed. The current study implies a tunable Re effect on creep via dislocation triggering at the phase interfaces. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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11 pages, 6646 KiB

Open AccessArticle

Effect of Repetitive Bending and Straightening Process on Microstructure Properties and Deformation Mechanism of a Ti–Al–Cr–Mo Alloy

by Zhuoliang Li, Yan Xu, Jiang Qian and Linhong Song

Materials 2023, 16(21), 6873; https://doi.org/10.3390/ma16216873 - 26 Oct 2023

Viewed by 683

Abstract

In this research, a repetitive bending and straightening process was carried out on the Ti–3Al–4Cr–Mo alloy for 20 passes. The changes in mechanical properties of the titanium alloy before and after repetitive bending and annealing were studied. The microstructure evolution and deformation mechanism were analyzed. The results show that after the repetitive bending and straightening process, the microstructure of the Ti–3Al–4Cr–Mo alloy is obviously refined, and, simultaneously, the yield strength is significantly improved. After annealing at 850 °C, the plastic ductility of the material was improved. The combined effects of grain refinement and dislocation behavior were the main reasons for the improvement in mechanical properties of the Ti–3Al–4Cr–Mo alloy. Twinning rarely occurred during plastic deformation of the Ti–3Al–4Cr–Mo alloy. The fine grains strongly inhibited the formation of twins. In addition, a small amount of α to β phase transformation was observed during the repetitive bending and straightening process of the material, which may have been induced by strain accumulation. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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14 pages, 10430 KiB

Open AccessArticle

Effect of Melt-Spinning Parameters on the Structure and Properties of Ni_55.5Mn_18.8Ga₂₄Si_1.7 Heusler Alloy Ribbons

by Pranav Bhale, Pnina Ari-Gur, Ronald D. Noebe, Yang Ren, Amila Madiligama, Ranjith Devaraj and Matthew S. Cook

Materials 2023, 16(19), 6590; https://doi.org/10.3390/ma16196590 - 07 Oct 2023

Cited by 1 | Viewed by 884

Abstract

Ni–Mn-based Heusler alloys are known to demonstrate magnetic shape memory and giant magnetocaloric effect (MCE). These effects depend on the phases, crystallographic and magnetic phase transitions, and the crystallographic texture characteristics. These structural characteristics, in turn, are a function of the processing parameters. In the current work, Ni_55.5Mn_18.8Ga₂₄Si_1.7 Heusler alloy was processed by melt-spinning under a helium atmosphere. This process results in a fine microstructure. The ribbon that was produced with a narrower nozzle width, faster wheel speed, and higher cast temperature, indicating a faster cooling rate, had double the magnetic entropy change close to room temperature. However, the other ribbon demonstrated a large entropy change over a broader temperature range, extending its usability. The effect of the melt-spinning process parameters on the developing microstructure, crystallographic structure and texture, transformation temperatures, and the magnetic entropy change were studied to explain the difference in magnetocaloric behavior. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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13 pages, 14817 KiB

Open AccessArticle

Long-Term Aging Study on the Solid State Interfacial Reactions of In on Cu Substrate

by Han-Tang Hung, Fu-Ling Chang, Chin-Hao Tsai, Chia-Yi Liao and C. R. Kao

Materials 2023, 16(18), 6263; https://doi.org/10.3390/ma16186263 - 18 Sep 2023

Viewed by 1233

Abstract

Indium is considered a candidate low-temperature solder because of its low melting temperature and excellent mechanical properties. However, the solid-state microstructure evolution of In with different substrates has rarely been studied due to the softness of In. To overcome this difficulty, cryogenic broad Ar⁺ beam ion polishing was used to produce an artifact-free Cu/In interface for observation. In this study, we accomplished phase identification and microstructure investigation at the Cu/In interface after long-term thermal aging. CuIn₂ was observed to grow at the Cu/In interface and proved to be a stable phase in the Cu–In binary system. The peritectoid temperature of the Cu₁₁In₉ + In → CuIn₂ reaction was confirmed to be between 100 and 120 °C. In addition, the growth rate of CuIn₂ was discovered to be dominated by the curvature of the reactant Cu₁₁In₉/In phase and the temperature difference with the peritectoid temperature. Finally, a comprehensive microstructural evolution mechanism of the Cu/In solid-state interfacial reaction was proposed. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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14 pages, 7842 KiB

Open AccessArticle

Influence of Solid Solutions on the Al2024 High-Temperature Deformation Behavior

by Oscar A. Ruano, Alberto Orozco-Caballero, Marta Álvarez-Leal and Fernando Carreño

Materials 2023, 16(18), 6251; https://doi.org/10.3390/ma16186251 - 17 Sep 2023

Viewed by 870

Abstract

The mechanical properties of 2024 aluminum alloy were studied after two different tempers. The T351 temper (solution heat treatment, stress relief, and natural aging) leads to high hardness and toughness. A thermal treatment consisting of heat-treating at 280 °C for 48 h and slow cooling in a furnace, named TT temper, was performed to increase the precipitate size and their separation while minimizing the amount of solutes in solid solution, which produced the minimum hardness for an overaged Al2024 alloy and a lower tensile flow stress than for the T351 temper. The flow stress strongly decreases and the elongation to failure strongly increases for both materials above 300 °C. Differences in strain rate at a given stress in the power law regime at all temperatures for both tempers and compared with pure aluminum are attributed to the influence of solutes in solid solutions, affecting both the glide and climb of dislocations. However, the stacking fault energy, SFE, alone does not account for the hot deformation behavior. Thus, it is the synergistic effect of various solutes that affects the entire deformation process, causing a decrease of three or four orders of magnitude in strain rate for a given stress with respect to the pure aluminum matrix values. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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11 pages, 5766 KiB

Open AccessArticle

Study on the Influence of Erbium and Preheating Process on Mechanical Properties of As-Cast 7055 Aluminum Alloy

by Jingwei Li and Faguo Li

Materials 2023, 16(15), 5296; https://doi.org/10.3390/ma16155296 - 27 Jul 2023

Cited by 1 | Viewed by 730

Abstract

Although 7055 aluminum alloy is a deformed aluminum alloy and shows excellent mechanical properties after recrystallization and large deformation, through this method, its application range is enriched if rare earth is added, and the rare earth phase dispersion is promoted by heat treatment. This article used optical microscopy, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), micro Vickers hardness, and room temperature stretching methods to study the as-cast 7055-xEr (x = 0 wt.%, 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.%) aluminum alloy after being subjected to 460 °C × 3 h homogenization and 410 °C × 1 h solid solution + 150 °C × 12 h aging treatment for the changes in its microstructure and properties. The results indicated that: when 0.2 wt.%Er was added to 7055 aluminum alloy after a solution at 410 °C × 1 h and aging at 150 °C × 12 h, the dendrite structure was significantly reduced, the grain thinning was obvious, and the distribution was uniform; the Al₈Cu₄Er phase appeared in the lamellar eutectic η-Mg(Zn,Al,Cu)₂ structure at grain boundaries, and the hardness reached 168.8 HV. The yield strength, tensile strength, and elongation were 542.12 MPa, 577.67 MPa, and 8.36%, respectively. Full article

(This article belongs to the Special Issue Microstructure Engineering of Metals and Alloys, Volume II)

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