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20 pages, 1746 KiB

Open AccessArticle

Surface Segregation Process and Its Influence on High-Temperature Corrosion of Iron-Based Alloys Containing Aluminium, Vanadium, Titanium and Germanium

by Magdalena Sobota, Karolina Idczak, Robert Konieczny and Rafał Idczak

Materials 2025, 18(3), 557; https://doi.org/10.3390/ma18030557 - 26 Jan 2025

Viewed by 338

Abstract

The surface segregation process and its influence on high-temperature corrosion of five alloys—Fe_0.95Al_0.05, Fe_0.95V_0.05, Fe_0.90Al_0.05V_0.05, Fe_0.95Ti_0.05 and Fe_0.95Ge_0.05—were studied using X-ray photoelectron [...] Read more.

The surface segregation process and its influence on high-temperature corrosion of five alloys—Fe_0.95Al_0.05, Fe_0.95V_0.05, Fe_0.90Al_0.05V_0.05, Fe_0.95Ti_0.05 and Fe_0.95Ge_0.05—were studied using X-ray photoelectron spectroscopy (XPS) and ⁵⁷Fe Transmission Mössbauer Spectroscopy (TMS). To prepare the alloys with the highest surface concentration of solutes, the samples were annealed at elevated temperatures to induce the surface segregation process. After that, they were exposed to air at 870 K for 1 and 5 h. It was found that the Fe_0.95Ti_0.05 sample annealed at 1073 K had much better anti–corrosion properties than other alloys studied. This finding can be correlated with the extremely high concentration of titanium on the surface, which was more than four times that of iron. In contrast to other alloys studied in this work, the passive layer formed on the surface of Fe_0.95Ti_0.05 greatly enhanced its resistance to corrosion. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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16 pages, 3713 KiB

Open AccessArticle

Analysis of the Distribution of Non-Metallic Inclusions and Its Impact on the Fatigue Strength Parameters of Carbon Steel Melted in an Electric Furnace

by Tomasz Lipiński

Materials 2024, 17(24), 6151; https://doi.org/10.3390/ma17246151 - 16 Dec 2024

Viewed by 507

Abstract

Steels are currently the most commonly used industrial construction materials. The use of steels depends on their properties, including their fatigue strength. Despite the fact that many works have been devoted to fatigue strength studies, there is still a lack of research discussing [...] Read more.

Steels are currently the most commonly used industrial construction materials. The use of steels depends on their properties, including their fatigue strength. Despite the fact that many works have been devoted to fatigue strength studies, there is still a lack of research discussing the fatigue strength of low-carbon steels. This deficiency is also visible when analyzing the influence of impurities on the fatigue properties of these steels. In most cases, the literature of material fatigue tests includes results obtained for materials produced on the laboratory scale, and it is difficult to directly translate these results to the industrial scale, on which steels for industrial applications are produced. This paper presents studies on the influence of non-metallic inclusions on the fatigue strength coefficient. The analyzed steel contained an average of 0.23% C, 1.23% Mn, and 0.0025 B. It was melted in 140-ton production furnaces, and after being tapped into a ladle, it was desulphurized and refined with argon. A classic plastic working process was used to produce steel samples. Based on the analysis of the test results, it was mainly found that the fatigue resistance coefficient k decreased with the increase in impurities spacing, and with a large share of smaller non-metallic inclusions, a higher fatigue resistance coefficient was noted, which may indicate that small non-metallic inclusions with an oval shape do not reduce the fatigue life of steel, regardless of its microstructure. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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20 pages, 5830 KiB

Open AccessArticle

A Quantitative Phase Analysis by Neutron Diffraction of Conventional and Advanced Aluminum Alloys Thermally Conditioned for Elevated-Temperature Applications

by Jordan Roger Kozakevich, Dimitry Sediako, David Weiss and Sven C. Vogel

Materials 2024, 17(17), 4311; https://doi.org/10.3390/ma17174311 - 30 Aug 2024

Viewed by 1009

Abstract

As the issue of climate change becomes more prevalent, engineers have focused on developing lightweight Al alloys capable of increasing the power density of powertrains. The characterization of these alloys has been focused on mechanical properties and less on the fundamental response of [...] Read more.

As the issue of climate change becomes more prevalent, engineers have focused on developing lightweight Al alloys capable of increasing the power density of powertrains. The characterization of these alloys has been focused on mechanical properties and less on the fundamental response of microstructures to achieve these properties. Therefore, this study assesses the quality of the microstructure of two high-temperature Al alloys (A356 + 3.5RE and Al-8Ce-10Mg), comparing them to T6 A356. These alloys underwent thermal conditioning at 250 and 300 °C for 200 h. Time-of-flight neutron diffraction experiments were performed before and after conditioning. The phase evolution was quantified using Rietveld refinement. It was found that the Si phase grows significantly (13–24%) in T6 A356, A356 + 3.5RE, and T6 A356 + 3.5RE alloys, which is typically correlated with a reduction in mechanical properties. Subjecting the A356 3.5RE alloy to a T6 heat treatment stabilizes the orthorhombic Al₄Ce₃Si₆ and monoclinic β-Al₅FeSi phases, making them resistant to thermal conditioning. These two phases are known for enhancing mechanical properties. Additionally, the T6 treatment reduced the vol.% of the cubic Al₂₀CeTi₂ and hexagonal ᴨ-Al₉FeSi₃Mg₅ phases by 13% and 23%, respectively. These phases have detrimental mechanical properties. The Al-8Ce-10Mg alloy cubic β-Al₃Mg₂ phase showed significant growth (82–101%) in response to conditioning, while the orthorhombic Al₁₁Ce₃ phase remained stable. The growth of the beta phase is known to decrease the mechanical properties of this alloy. These efforts give valuable insight into how these alloys will perform and evolve in demanding high-temperature environments. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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11 pages, 2613 KiB

Open AccessArticle

Manufacturing of Ni-Co-Fe-Cr-Al-Ti High-Entropy Alloy Using Directed Energy Deposition and Evaluation of Its Microstructure, Tensile Strength, and Microhardness

by Ho-In Jeong, Jae-Hyun Kim and Choon-Man Lee

Materials 2024, 17(17), 4297; https://doi.org/10.3390/ma17174297 - 30 Aug 2024

Cited by 1 | Viewed by 985

Abstract

High-entropy alloys (HEAs) have drawn significant attention due to their unique design and superior mechanical properties. Comprising 5–35 at% of five or more elements with similar atomic radii, HEAs exhibit high configurational entropy, resulting in single-phase solid solutions rather than intermetallic compounds. Additive [...] Read more.

High-entropy alloys (HEAs) have drawn significant attention due to their unique design and superior mechanical properties. Comprising 5–35 at% of five or more elements with similar atomic radii, HEAs exhibit high configurational entropy, resulting in single-phase solid solutions rather than intermetallic compounds. Additive manufacturing (AM), particularly direct energy deposition (DED), is effective for producing HEAs due to its rapid cooling rates, which ensure uniform microstructures and minimize defects. These alloys typically form face-centered cubic (FCC) or body-centered cubic (BCC) structures, contributing to their exceptional strength, hardness, and mechanical performance across various temperatures. However, FCC-structured HEAs often have low yield strengths, posing a challenge for structural applications. In this study, a Ni-Co-Fe-Cr-Al-Ti HEA was manufactured using the DED method. This study proposes that the addition of aluminum and titanium creates a γ + γ′ phase structure within a multicomponent FCC-HEA matrix, enhancing the thermal stability and coarsening the resistance and strength. The γ′ phase with an ordered FCC structure significantly improves the mechanical properties. Analysis confirmed the presence of the γ + γ′ structure and demonstrated the alloy’s high tensile strength and microhardness. This approach underscores the potential of AM techniques in advancing HEA production for high-performance applications. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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18 pages, 7843 KiB

Open AccessArticle

Effect of La on the Microstructures and Mechanical Properties of Al-5.4Cu-0.7Mg-0.6Ag Alloys

by Xiang Li, Anmin Li, Xiangdu Qin, Hailong Yang and Peng Cheng

Materials 2024, 17(16), 4141; https://doi.org/10.3390/ma17164141 - 21 Aug 2024

Viewed by 726

Abstract

The effects of the rare earth element La on the microstructure and mechanical properties of cast Al-5.4Cu-0.7Mg-0.6Ag alloys have been investigated through metallographic observation, scanning electron microscopy analysis, transmission electron microscopy, X-ray diffraction, and tensile testing. The present form and action mechanism of [...] Read more.

The effects of the rare earth element La on the microstructure and mechanical properties of cast Al-5.4Cu-0.7Mg-0.6Ag alloys have been investigated through metallographic observation, scanning electron microscopy analysis, transmission electron microscopy, X-ray diffraction, and tensile testing. The present form and action mechanism of La have been analyzed. The findings indicate that the inclusion of trace amounts of La markedly diminishes the grain size in the Al-Cu-Mg-Ag alloy. Furthermore, as the La content increases, the alloy’s strength is significantly improved. When the La concentration reaches 0.4 wt.%, the mechanical properties of the alloy, both at room temperature and at 350 °C, surpass those of the alloy lacking rare earth elements. When the added rare earth La content exceeds 0.2 wt.%, the emergence of the Al₆Cu₆La phase causes the alloy structure to exhibit a skeletal morphology, altering the morphology and distribution of excess second phases along grain boundaries, thereby impacting the alloy’s overall performance. Incorporating La leads to a reduction in the size of the strengthening precipitate phase Ω while also enhancing its precipitation density, but an excess of La leads to the emergence of Al₆Cu₆La, depleting the available Cu and suppressing the precipitation of the Ω phase, ultimately affecting the mechanical properties of the alloy. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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21 pages, 7357 KiB

Open AccessArticle

Design and Control of the Natural Frequency of Brake Discs in the Aspect of the Gray Cast Iron Production Process

by Andrzej Zyska, Mariusz Bieroński, Krzysztof Naplocha and Paweł Popielarski

Materials 2024, 17(14), 3490; https://doi.org/10.3390/ma17143490 - 14 Jul 2024

Viewed by 1063

Abstract

The results of research on the influence of the chemical composition of cast iron and its potential changes in the production cycle on the elastic properties and the correctness of numerical simulations of the natural frequency of ventilated brake discs are presented. The [...] Read more.

The results of research on the influence of the chemical composition of cast iron and its potential changes in the production cycle on the elastic properties and the correctness of numerical simulations of the natural frequency of ventilated brake discs are presented. The tests were carried out for three grades of gray cast iron with flake graphite with a eutectic saturation coefficient ranging from 0.88 to 1.01. A quantitative metallographic assessment of the pearlitic cast iron matrix and graphite precipitates was carried out, and the hardness and compressive/tensile strength of individual cast iron grades were determined, taking into account the limit contents of the alloying elements. Next, ultrasonic tests were performed, and the elastic properties of cast iron were determined. Based on the obtained data, a numerical modal analysis of brake discs was performed, the results of which were compared with the actual values of an FRF frequency analysis. The error of the computer simulations was estimated at approx. 1%, and it was found that the accuracy of the calculations of the first natural frequency did not depend on the dimensions (size) of the discs and the chemical composition of the cast iron from which they were cast. The functional relationships between the chemical composition of cast iron, its strength and elasticity and the first natural frequency of the disc vibrations were determined, and a database of the material parameters of the produced cast iron grades was developed. An implementation example showed the validation of the brake disc design with natural frequency prediction and demonstrated a high convergence of the experimental results with the simulated values. Using I-MR control cards, both the effectiveness of designing and predicting the natural vibrations of brake discs based on the implemented material database as well as the stability of the gray cast iron production and disc casting processes were confirmed. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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14 pages, 5705 KiB

Open AccessArticle

Effect of Secondary Phase on Passivation Layer of Super Duplex Stainless Steel UNS S 32750: Advanced Safety of Li-Ion Battery Case Materials

by Byung-Hyun Shin, Seongjun Kim, Jinyong Park, Jung-Woo Ok, Dohyung Kim and Jang-Hee Yoon

Materials 2024, 17(11), 2760; https://doi.org/10.3390/ma17112760 - 5 Jun 2024

Cited by 2 | Viewed by 1094

Abstract

Aluminum, traditionally the primary material for battery casings, is increasingly being replaced by UNS S 30400 for enhanced safety. UNS S 30400 offers superior strength and corrosion resistance compared to aluminum; however, it undergoes a phase transformation owing to stress during processing and [...] Read more.

Aluminum, traditionally the primary material for battery casings, is increasingly being replaced by UNS S 30400 for enhanced safety. UNS S 30400 offers superior strength and corrosion resistance compared to aluminum; however, it undergoes a phase transformation owing to stress during processing and a lower high-temperature strength. Duplex stainless steel UNS S 32750, consisting of both austenite and ferrite phases, exhibits excellent strength and corrosion resistance. However, it also precipitates secondary phases at high temperatures, which are known to form through the segregation of Cr and Mo. Various studies have investigated the corrosion resistance of UNS S 32750; however, discrepancies exist regarding the formation and thickness of the passivation layer. This study analyzed the oxygen layer on the surface of UNS S 32750 after secondary-phase precipitation. The microstructure, volume fraction, chemical composition, and depth of O after the precipitation of the secondary phases in UNS S 32750 was examined using FE-SEM, EDS, EPMA and XRD, and the surface chemical composition and passivation layer thickness were analyzed using electron probe microanalysis and glow-discharge spectroscopy. This study demonstrated the segregation of alloy elements and a reduction in the passivation-layer thickness after precipitation from 25 μm to 20 μm. The findings of the analysis aid in elucidating the impact of secondary-phase precipitation on the passivation layer. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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11 pages, 1777 KiB

Open AccessArticle

Orientation-Dependent Mechanical Behaviors of BCC-Fe in Light of the Thermo-Kinetic Synergy of Plastic Deformation

by Yu Liu, Jinglian Du, Kunyu Zhang, Kangxu Gao, Haotian Xue, Xiao Fang, Kexing Song and Feng Liu

Materials 2024, 17(10), 2395; https://doi.org/10.3390/ma17102395 - 16 May 2024

Viewed by 843

Abstract

The orientation-dependent mechanical behaviors of metallic alloys are governed by deformation mechanisms, but the underlying physics remain to be explored. In this work, the mechanical responses along different orientations and behind the mechanisms of BCC-Fe are investigated by performing molecular dynamic simulations. It [...] Read more.

The orientation-dependent mechanical behaviors of metallic alloys are governed by deformation mechanisms, but the underlying physics remain to be explored. In this work, the mechanical responses along different orientations and behind the mechanisms of BCC-Fe are investigated by performing molecular dynamic simulations. It is found that the mechanical properties of BCC-Fe exhibit apparent anisotropic characteristics. The <100>-oriented BCC-Fe presents a Young’s modulus of E = 147.56 GPa, a strength of σ_y = 10.15 GPa, and a plastic strain of ε_y = 0.084 at the yield point, whereas the <111> orientation presents E = 244.84 GPa, σ_y = 27.57 GPa, and ε_y = 0.21. Based on classical dislocation theory, the reasons for such orientation-dependent mechanical behaviors are analyzed from the perspective of thermo-kinetic synergy upon deformation. It turns out that the anisotropic mechanical responses of BCC-Fe are associated with the magnitude of the thermodynamic driving force (ΔG) and kinetic energy barrier (Q) for dislocation motion, which dominate the corresponding deformation mechanism. Compared with the low ΔG (6.395 GPa) and high Q (11.95 KJ/mol) of the <100>-oriented BCC-Fe dominated by deformation twinning, the <111> orientation governed by dislocation slip presents a high ΔG (17.37 GPa) and low Q (6.45 KJ/mol). Accordingly, the orientation-dependent deformation behaviors of BCC-Fe are derived from the thermo-kinetic synergy for dislocation motion. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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26 pages, 12774 KiB

Open AccessArticle

Contributions to a More Realistic Characterization of Corrosion Processes on Cut Edges of Coated Metals Using Scanning Microelectrochemical Techniques, Illustrated by the Case of ZnAlMg-Galvanized Steel with Different Coating Densities

by Marilia Fernandes Bolsanello, Andrea Abreu García, Luciana Xavier da Cruz Lima, Bruno Kneipel Neto, Jetson Lemos Ferreira, Jesualdo Luiz Rossi, Isolda Costa, Ricardo M. Souto and Javier Izquierdo

Materials 2024, 17(7), 1679; https://doi.org/10.3390/ma17071679 - 5 Apr 2024

Viewed by 1529

Abstract

Corrosion processes at cut edges of galvanized steels proceed as highly localized electrochemical reactions between the exposed bulk steel matrix and the protective thin metallic coating of a more electrochemically active material. Scanning microelectrochemical techniques can thus provide the spatially resolved information needed [...] Read more.

Corrosion processes at cut edges of galvanized steels proceed as highly localized electrochemical reactions between the exposed bulk steel matrix and the protective thin metallic coating of a more electrochemically active material. Scanning microelectrochemical techniques can thus provide the spatially resolved information needed to assess the corrosion initiation and propagation phenomena, yet most methods scan cut edge sections as embedded in insulating resin to achieve a flat surface for scanning purposes. In this work, the galvanized coatings on both sides of the material were concomitantly exposed to simulated acid rain while characterizing the cut edge response using SECM and SVET techniques, thereby maintaining the coupled effects through the exposure of the whole system as rather realistic operation conditions. The cut edges were shown to strongly promote oxygen consumption and subsequent alkalization to pH 10–11 over the iron, while diffusion phenomena eventually yielded the complete depletion of oxygen and pH neutralization of the nearby electrolyte. In addition, the cathodic activation of the exposed iron was intensified with a thinner coating despite the lower presence of sacrificial anode, and preferential sites of the attack in the corners revealed highly localized acidification below pH 4, which sustained hydrogen evolution at spots of the steel-coating interface. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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12 pages, 3476 KiB

Open AccessArticle

Atomic Diffusivities of Yttrium, Titanium and Oxygen Calculated by Ab Initio Molecular Dynamics in Molten 316L Oxide-Dispersion-Strengthened Steel Fabricated via Additive Manufacturing

by Zhengming Wang, Seongun Yang, Stephanie B. Lawson, V. Vinay K. Doddapaneni, Marc Albert, Benjamin Sutton, Chih-Hung Chang, Somayeh Pasebani and Donghua Xu

Materials 2024, 17(7), 1543; https://doi.org/10.3390/ma17071543 - 28 Mar 2024

Cited by 2 | Viewed by 1698

Abstract

Oxide-dispersion-strengthened (ODS) steels have long been viewed as a prime solution for harsh environments. However, conventional manufacturing of ODS steels limits the final product geometry, is difficult to scale up to large components, and is expensive due to multiple highly involved, solid-state processing [...] Read more.

Oxide-dispersion-strengthened (ODS) steels have long been viewed as a prime solution for harsh environments. However, conventional manufacturing of ODS steels limits the final product geometry, is difficult to scale up to large components, and is expensive due to multiple highly involved, solid-state processing steps required. Additive manufacturing (AM) can directly incorporate dispersion elements (e.g., Y, Ti and O) during component fabrication, thus bypassing the need for an ODS steel supply chain, the scale-up challenges of powder processing routes, the buoyancy challenges associated with casting ODS steels, and the joining issues for net-shape component fabrication. In the AM process, the diffusion of the dispersion elements in the molten steel plays a key role in the precipitation of the oxide particles, thereby influencing the microstructure, thermal stability and high-temperature mechanical properties of the resulting ODS steels. In this work, the atomic diffusivities of Y, Ti, and O in molten 316L stainless steel (SS) as functions of temperature are determined by ab initio molecular dynamics simulations. The latest Vienna Ab initio Simulation Package (VASP) package that incorporates an on-the-fly machine learning force field for accelerated computation is used. At a constant temperature, the time-dependent coordinates of the target atoms in the molten 316L SS were analyzed in the form of mean square displacement in order to obtain diffusivity. The values of the diffusivity at multiple temperatures are then fitted to the Arrhenius form to determine the activation energy and the pre-exponential factor. Given the challenges in experimental measurement of atomic diffusivity at such high temperatures and correspondingly the lack of experimental data, this study provides important physical parameters for future modeling of the oxide precipitation kinetics during AM process. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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17 pages, 7395 KiB

Open AccessEditor’s ChoiceArticle

Influence of Surface Preparation on the Microstructure and Mechanical Properties of Cold-Sprayed Nickel Coatings on Al 7075 Alloy

by Wojciech Żórawski, Anna Góral, Medard Makrenek, Lidia Lityńska-Dobrzyńska and Paweł Czaja

Materials 2023, 16(21), 7002; https://doi.org/10.3390/ma16217002 - 1 Nov 2023

Cited by 2 | Viewed by 1240

Abstract

This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation [...] Read more.

This work presents the effect of surface roughness (Al 7075) on the microstructure and mechanical properties of cold-sprayed nickel coatings. Coating analysis included substrate surfaces and coating geometry, microstructure characterization, microhardness, nanohardness, elastic modulus, and adhesion. The results show that the surface preparation had a significant effect on coating adhesion and microstructure. The coating deposited at the highest gas temperature revealed a dense microstructure, showing very good adhesion of the impacting powder particles to the substrate and good bonding between deposited layers. The Ni grains with different shapes (elongated, equiaxed) and sizes of a few dozen to several hundred nanometres were present in the splats. An increase in temperature caused significant growth in coating thickness as a result of the powder grains’ higher velocity. Moreover, higher gas temperature resulted in the enhancement of micro- and nanohardness, elastic modulus, and adhesion. The adhesive bond strength of Ni coatings in the tested temperature ranges from 500 °C to 800 °C increased with the increase in the surface roughness of the substrate. For the Al 7075 coarse grit-blasted (CG) substrate with the highest roughness, the adhesion reached the highest value of 44.6 MPa when the working gas was at a temperature of 800 °C. There were no distinct dependencies of surface roughness and thickness on the mechanical properties of the cold-sprayed nickel coating. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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14 pages, 10278 KiB

Open AccessEditor’s ChoiceArticle

The Characteristic of

{10 \bar{1} 2} < 10 \bar{1} \bar{1} >

Twin of Ti-10V-2Fe-3Al under Planar Wave Detonation

by Tong Wang, Ping Yang, Jin Zhang and Xin-Fu Gu

Materials 2023, 16(20), 6739; https://doi.org/10.3390/ma16206739 - 18 Oct 2023

Cited by 1 | Viewed by 1276

Abstract

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to [...] Read more.

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from

{10 \bar{1} 0}

to

{0002}

during the deformation due to the

{10 \bar{1} 2} < 10 \bar{1} \bar{1} >

twin. Twin variant selection is found in this study, and the orientation of all

{10 \bar{1} 2}

twins is oriented at

{0002}

in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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14 pages, 6088 KiB

Open AccessArticle

Stainless Steel in Municipal Sewage—How to Recognize Favorable Corrosion Conditions

by Paweł Lochyński, Magdalena Domańska, Robert Dziedzic and Kamila Hamal

Materials 2023, 16(20), 6637; https://doi.org/10.3390/ma16206637 - 11 Oct 2023

Cited by 1 | Viewed by 1087

Abstract

While chromium–nickel steel is known to be extremely resistant to corrosion, the occurrence of certain factors can unfortunately initiate an uncontrolled corrosion process. This paper presents samples made of 304 stainless steel containing delta ferrite that have been exposed to wastewater for 18 [...] Read more.

While chromium–nickel steel is known to be extremely resistant to corrosion, the occurrence of certain factors can unfortunately initiate an uncontrolled corrosion process. This paper presents samples made of 304 stainless steel containing delta ferrite that have been exposed to wastewater for 18 months. Samples placed above the surface of the wastewater (A-series) were intensively corroded. Samples half-submerged in the wastewater and periodically fully submerged at higher effluent flows through the screenings and grit separator (B-series) only suffered minor mechanical erosion. No significant changes in the tested surface were observed on samples fully submerged in wastewater (C-series). The results indicated that the observed pitting corrosion of samples placed above the surface of the wastewater was a consequence of the presence of bacteria in a wet hydrogen sulfide environment. The fluorescence in situ hybridization method showed that either the sludge taken from the wastewater, or from the surface of samples submerged in wastewater exhibited increased amounts of bacteria from the δ-proteobacteria class, indicating the presence of microorganisms involved in the reduction of sulfur or sulfate compounds. A new approach to microbiological evaluation by determining classes of bacteria may be a promising tool for evaluating wastewater in terms of aggressiveness and recognizing favorable corrosive conditions. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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Review

Jump to: Research

38 pages, 18491 KiB

Open AccessReview

Review of the Microstructural Impact on Creep Mechanisms and Performance for Laser Powder Bed Fusion Inconel 718

by Guillian Bryndza, Jérôme Tchoufang Tchuindjang, Fan Chen, Anne Marie Habraken, Héctor Sepúlveda, Víctor Tuninetti, Anne Mertens and Laurent Duchêne

Materials 2025, 18(2), 276; https://doi.org/10.3390/ma18020276 - 9 Jan 2025

Viewed by 693

Abstract

Inconel 718 (IN718) is a polycrystalline nickel-based superalloy and one of the most widely used materials in the aerospace industry owing to its excellent mechanical performances at high temperatures, including creep resistance. Interest in additively manufactured components in aerospace is greatly increasing due [...] Read more.

Inconel 718 (IN718) is a polycrystalline nickel-based superalloy and one of the most widely used materials in the aerospace industry owing to its excellent mechanical performances at high temperatures, including creep resistance. Interest in additively manufactured components in aerospace is greatly increasing due to their ability to reduce material consumption, to manufacture complex parts, and to produce out-of-equilibrium microstructures, which can be beneficial for mechanical behavior. IN718’s properties are, however, very sensitive to microstructural features, which strongly depend on the manufacturing process and subsequent heat treatments. Additive manufacturing and, more specifically, Laser Powder Bed Fusion (LPBF) induces very high thermal gradients and anisotropic features due to its inherently directional nature, which largely defines the microstructure of the alloy. Hence, defining appropriate manufacturing parameters and heat treatments is critical to obtain appropriate mechanical behavior. This review aims to present the main microstructural features of IN718 produced by LPBF, the creep mechanisms taking place, the optimal microstructure for creep strength, and the most efficient heat treatments to yield such an optimized microstructure. Full article

(This article belongs to the Special Issue Quality, Microstructure and Properties of Metal Alloys (Second Volume))

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