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Special Issue "Microstructure Engineering of Metals and Alloys"

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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: 10 June 2023 | Viewed by 6157

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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,

Metals and alloys are a class of materials which combines high mechanical properties as strength, ductility, and stiffness with high physical properties 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 other).

Both material’s structure, formed of one, two or more phases and structural defects (vacancies, dislocations, grain boundaries, and other) affect their properties. Therefore, microstructure engineering is an effective approach to achieve a 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 being commonly carried out using optical microscope. However, from the middle of the 20-th century, electron microscopy (EM) became a more effective method of structural evaluation. Microstructure characterization with EM makes available “deep view” into the metal. Thus, recent progress in understanding of structural formation of some metals may be referred to development and implementation of electron microscopy. However, this tool is not the exclusive, other available techniques are also valuable in understanding of the metallic structure. Thus, X-ray and electron diffraction analysis responsible for the phase detection, and electron backscatter diffraction provides crystallographic information.

The scope of the Special Issue will focus on recent innovations in the field of 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 in the form of a full paper, communication, or a review to 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 2300 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

Open AccessArticle

Investigation of the Technological Possibility of Manufacturing Volumetric Shaped Ductile Cast Iron Products in Open Dies

and

Materials 2023, 16(1), 274; https://doi.org/10.3390/ma16010274 - 28 Dec 2022

Viewed by 608

Abstract

Information about the technological possibility of stamping in open dies, round-shaped forgings made of ductile cast iron, is outlined herein. Cast iron’s propensity for plastic deformation under complex loading conditions is analyzed from the standpoint of the morphology of graphite inclusions, depending on the degree and mechanical scheme of deformation. The research methodology included: the choice of a brand of cast iron with spherical graphite and the technological process of its deformation; mathematical modeling of the deformation process using the DEFORM–3D software package; stamping of an experimental batch of forgings; and microstructural studies of the forging material, together with the data of its stress–strain state and the direction of flow of the material. Under the conditions of comprehensive compression of the workpiece material at the beginning of the deformation process, lateral pressure was created from the tool walls. It was carried out by selecting the size and shape of the initial blank by mathematical modeling. When analyzing the morphology of graphite inclusions, the stress state scheme was determined as the main influencing factor. The greatest change in the shape and size of graphite inclusions of cast iron, including their crushing, corresponds to the condition of the disappearance of all-round compression. When stamping in open dies, this occurs in the area where the material exits from the stamp engraving into the flash gutter. In the process of forming, cast iron showed the possibility of deformation in the deformation intensity index ε_i = 2.5. Full article

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

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Open AccessArticle

Experimental Research on Sheared Edge Formation in the Shear-Slitting of Grain-Oriented Electrical Steel Workpieces

Monika Szada-Borzyszkowska

and

Kamil Banaszek

Materials 2022, 15(24), 8824; https://doi.org/10.3390/ma15248824 - 10 Dec 2022

Viewed by 374

Abstract

This study sought to experimentally develop guidelines for shaping 0.3-mm-thick cold-rolled grain-oriented ET 110-30LS steel using a shear-slitting operation. Coated and non-coated steel was used for the analysis. The coated sheet had a thin inorganic C-5 coating on both sides applied to the C-2 substrate. The first part of this paper presents an analysis of the quality of the cut surface depending on the adopted machining parameters, which were the control variables on the production lines. The second part presents an analysis of the magnetic parameters of the cut samples, which allowed for the specific impact of the quality of the cut edge on the selected magnetic features. Finally, an optimization task was developed to obtain a set of acceptable solutions on the plane of controllable process variables such as slitting speed and horizontal clearance. The obtained results can be used to control the shear-slitting process on production lines and obtain high-quality workpieces. Full article

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

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Open AccessArticle

Investigation of Low-Pressure Sn-Passivated Cu-to-Cu Direct Bonding in 3D-Integration

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Materials 2022, 15(21), 7783; https://doi.org/10.3390/ma15217783 - 04 Nov 2022

Viewed by 576

Abstract

Cu-to-Cu direct bonding plays an important role in three-dimensional integrated circuits (3D IC). However, the bonding process always requires high temperature, high pressure, and a high degree of consistency in height. In this study, Sn is passivated over electroplated copper. Because Sn is a soft material and has a low melting point, a successful bond can be achieved under low temperature and low pressure (1 MPa) without any planarization process. In this experiment, Sn thickness, bonding temperature, and bonding pressure are variables. Three values of thicknesses of Sn, i.e., 1 μm, 800 nm, and 600 nm were used to calculate the minimum value of Sn thickness required to compensate for the height difference. Additionally, the bonding process was conducted at two temperatures, 220 °C and 250 °C, and their optimized parameters with required pressure were found. Moreover, the optimized parameters after the Cu planarization were also investigated, and it was observed that the bonding can succeed under severe conditions as well. Finally, transmission electron microscopy (TEM) was used to observe the adhesion property between different metals and intermetallic compounds (IMCs). Full article

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

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Open AccessArticle

Fiber Laser Welded Cobalt Super Alloy L605: Optimization of Weldability Characteristics

B. Hari Prasad

G. Madhusudhan Reddy

Alok Kumar Das

and

Konda Gokuldoss Prashanth

Materials 2022, 15(21), 7708; https://doi.org/10.3390/ma15217708 - 02 Nov 2022

Viewed by 623

Abstract

The present study describes the laser welding of Co-based superalloy L605 (52Co-20Cr-10Ni-15W) equivalent to Haynes-25 or Stellite-25. The influence of laser welding process input parameters such as laser beam power and welding speed on mechanical and metallurgical properties of weld joints were investigated. Epitaxial grain growth and dendritic structures were visible in the weld zone. The phase analysis results indicate the formation of hard phases like CrFeNi, CoC, FeNi, and CFe in the weld zone. These hard phases are responsible for the increase in microhardness up to 321 HV_0.1 in the weld zone, which is very close to the microhardness of the parent material. From the tensile strength tests, the ductile failure of welded specimens was confirmed due to the presence of dimples, inter-granular cleavage, and micro voids in the fracture zone. The maximum tensile residual stress along the weld line is 450 MPa, whereas the maximum compressive residual stress across the weld line is 500 MPa. On successful application of Response Surface methodology (RSM), laser power of 1448.5 W and welding speed of 600 mm/min i.e., line energy or heat input equal to 144 J/mm, were found to be optimum values for getting sound weld joint properties. The EBSD analysis reveals the elongated grain growth in the weld pool and very narrow grain growth in the heat-affected zone. Full article

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

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Open AccessArticle

Characterization of Inclusion Size Distributions in Steel Wire Rods

Pablo Huazano-Estrada

Martín Herrera-Trejo

Manuel de J. Castro-Román

and

Jorge Ruiz-Mondragón

Materials 2022, 15(21), 7681; https://doi.org/10.3390/ma15217681 - 01 Nov 2022

Viewed by 507

Abstract

The control of inclusions in steel components is essential to guarantee strong performance. The reliable characterization of inclusion populations is essential not only to evaluate the quality of the components but also to allow the use of analytical procedures for the comparison and discrimination of inclusion populations. In this work, inclusion size distributions in wire rod specimens from six plant-scale heats were measured and analyzed. For the measurements, the metallographic procedure specified in the ASTM E2283 standard was used. The population density function (PDF) approach and the extreme value statistical procedure specified in the ASTM E2283 standard were used to analyze the whole size distribution and the upper tail of the size distribution, respectively. The PDF approach allowed us to identify differences among inclusion size distributions and showed that new inclusions were not formed after the liquid steel treatment process. The extreme value statistical procedure led to the prediction of the maximum inclusion length for each heat, which was used for the statistical discrimination of heats. Furthermore, the estimation of the probability of finding an inclusion larger than a given inclusion size using the extreme value theory allowed us to order the heats for different critical inclusion sizes. Full article

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

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Open AccessArticle

Heterogeneous Multiphase Microstructure Formation through Partial Recrystallization of a Warm-Deformed Medium Mn Steel during High-Temperature Partitioning

and

Materials 2022, 15(20), 7322; https://doi.org/10.3390/ma15207322 - 19 Oct 2022

Viewed by 574

Abstract

A novel processing route is proposed to create a heterogeneous, multiphase structure in a medium Mn steel by incorporating partial quenching above the ambient, warm deformation, and partial recrystallization at high partitioning temperatures. The processing schedule was implemented in a Gleeble thermomechanical simulator and microstructures were examined by electron microscopy and X-ray diffraction. The hardness of the structures was measured as the preliminary mechanical property. Quenching of the reaustenitized sample to 120 °C provided a microstructure consisting of 73% martensite and balance (27%) untransformed austenite. Subsequent warm deformation at 500 °C enabled partially recrystallized ferrite and retained austenite during subsequent partitioning at 650 °C. The final microstructure consisted of a heterogeneous mixture of several phases and morphologies including lath-tempered martensite, partially recrystallized ferrite, lath and equiaxed austenite, and carbides. The volume fraction of retained austenite was 29% with a grain size of 200–300 nm and an estimated average stacking fault energy of 45 mJ/m². The study indicates that desired novel microstructures can be imparted in these steels through suitable process design, whereby various hardening mechanisms, such as transformation-induced plasticity, bimodal grain size, phase boundary, strain partitioning, and precipitation hardening can be activated, resulting presumably in enhanced mechanical properties. Full article

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

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Open AccessArticle

Casting and Characterization of A319 Aluminum Alloy Reinforced with Graphene Using Hybrid Semi-Solid Stirring and Ultrasonic Processing

Bernoulli Andilab

Payam Emadi

and

Comondore Ravindran

Materials 2022, 15(20), 7232; https://doi.org/10.3390/ma15207232 - 17 Oct 2022

Cited by 1 | Viewed by 525

Abstract

Advanced metallurgical processing techniques are required to produce aluminum matrix composites due to the tendency of the reinforcement particles to agglomerate. In this study, graphene nano-platelet reinforcement particles were effectively incorporated into an automotive A319 aluminum alloy matrix using a liquid metallurgical route. Due to its low density, it is a highly difficult task to produce an aluminum matrix composite reinforced with graphene. Hence, this study explored a novel approach to prevent particle floating to the melt surface and agglomeration. This was achieved via a hybrid semi-solid stirring of A319, followed by ultrasonic treatment of the liquid melt using a sonication probe. The microstructure and graphene particles were characterized using optical microscopy and scanning electron microscopy. Furthermore, the interfacial products produced with the incorporation of graphene in liquid aluminum were analyzed with X-ray diffraction. The tensile test results exhibited 10, 11 and 32% improvements in ultimate tensile strength, yield strength, and ductility of A319 reinforced with 0.05 wt.% addition of graphene. Analysis of strengthening models demonstrated primary contribution from Hall-Petch followed by CTE mismatch and load bearing mechanism. The results from this research enable the potential for using cost-effective, efficient and simple liquid metallurgy methods to produce aluminum reinforced graphene composites with improved mechanical properties. Full article

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

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Open AccessArticle

Study on the Effect of Pre-Refinement and Heat Treatment on the Microstructure and Properties of Hypoeutectic Al-Si-Mg Alloy

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Materials 2022, 15(17), 6056; https://doi.org/10.3390/ma15176056 - 01 Sep 2022

Viewed by 587

Abstract

Hypoeutectic Al-Si-Mg alloys with a silicon content of around 10 wt % are widely used in the aerospace and automotive fields due to their excellent casting properties. However, the occurrence of “silicon poisoning” weakens the refinement effect of a conventional refiner system such as Al-5Ti-1B. In this paper, we proposed the “pre-refinement” method to avoid the “Si poisoning” to recover the refinement effect of Al-5Ti-1B. The core concept was to adjust the order of adding the Si element to form the TiAl₃ before forming the Ti-Si intermetallic compound. To prove the effectiveness of the “pre-refinement” method, three alloys of “pre-refinement”, “post-refinement”, and “non-refinement” of an Al-10Si-0.48Mg alloy were prepared and characterized in as-cast and heat-treatment states. The results showed that the average grain diameter of the “pre-refinement” alloy was 60.19% smaller than that of the “post-refinement” one and 81.34% smaller than that of the “non-refinement” one, which demonstrated that the proposed method could effectively avoid the “silicon poisoning” effect. Based on a refined grain size, the “pre-refinement” Al-10Si-0.48Mg alloy showed the best optimization effect in mechanical properties after a solid-solution and subsequent aging heat treatments. The best mechanical properties were found in the “pre-refinement” alloy with 2 h of solid solution treatment and 10 h of aging treatment: a hardness of 92 HV, a tensile strength of 212 MPa, and an elongation of 20%. Full article

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

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Open AccessArticle

Development of a Thermomechanical Treatment Mode for Stainless-Steel Rings

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Materials 2022, 15(14), 4930; https://doi.org/10.3390/ma15144930 - 15 Jul 2022

Cited by 11 | Viewed by 617

Abstract

This article describes a technology for the thermomechanical treatment of stainless-steel piston rings. This technology makes it possible to obtain rings with an optimal combination of plastic and strength properties that is essential for piston rings. The following thermomechanical treatment is suggested for piston rings manufacturing: quenching at 1050 °C, holding for 30 min and cooling in water, then straining by the HPT method for eight cycles at cryogenic temperature and annealing at a temperature up to 600 °C. The resulting microstructure consisted of fine austenite grains sized 0.3 μm and evenly distributed carbide particles. Annealing above this temperature led to the formation of ferrite in the structure; however, preserving the maximum fraction of austenitic component is very important, since the reduction of austenite in the structure will cause a deterioration of corrosion resistance. The strength properties of steel after such treatment increased by almost two times compared with the initial ones: microhardness increased from 980 MPa to 2425 MPa, relative elongation increased by 20%. The proposed technology will improve the strength and performance characteristics of piston rings, as well as increase their service life, which will lead to significant savings in the cost of repair, replacement and downtime. Full article

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

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Open AccessArticle

Precipitation Evolution in the Austenitic Heat-Resistant Steel HR3C upon Creep at 700 °C and 750 °C

and

Materials 2022, 15(13), 4704; https://doi.org/10.3390/ma15134704 - 05 Jul 2022

Viewed by 725

Abstract

HR3C (25Cr-20Ni-Nb-N) is a key material used in heat exchangers in supercritical power plants. Its creep properties and microstructural evolution has been extensively studied at or below 650 °C. The precipitation evolution in HR3C steel after creep rupture at elevated temperatures of 700 °C and 750 °C with a stress range of 70~180 MPa is characterized in this paper. The threshold strength at 700 °C and 750 °C were determined by extrapolation method to be

σ_{10^{5}}^{700} =

57.1 MPa and

σ_{10^{5}}^{750} =

37.5 MPa, respectively. A corresponding microstructure investigation indicated that the main precipitates precipitated during creep exposure are Z-phase (NbCrN), M₂₃C₆, and σ phase. The dense Z-phase precipitated dispersively in the austenite matrix along dislocation lines, and remained stable (both size and fraction) during long-term creep exposure. M₂₃C₆ preferentially precipitated at grain boundaries, and coarsening was observed in all creep specimens with some continuous precipitation of granular M₂₃C₆ in the matrix. The brittle σ phase formed during a relatively long-term creep, whose size and fraction increased significantly at high temperature. Moreover, the σ phases, grown and connected to form a large “island” at triple junctions of grain boundaries, appear to serve as nucleation sites for high stress concentration and creep cavities, weakening the grain boundary strength and increasing the sensitivity to intergranular fracture. Full article

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

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