Metals

17 pages, 7068 KiB

Open AccessArticle

Effect of Ni-Based Buttering on the Microstructure and Mechanical Properties of a Bimetallic API 5L X-52/AISI 316L-Si Welded Joint

by Luis Ángel Lázaro-Lobato, Gildardo Gutiérrez-Vargas, Francisco Fernando Curiel-López, Víctor Hugo López-Morelos, María del Carmen Ramírez-López, Julio Cesar Verduzco-Juárez and José Jaime Taha-Tijerina

Metals 2025, 15(8), 824; https://doi.org/10.3390/met15080824 - 23 Jul 2025

Abstract

The microstructure and mechanical properties of welded joints of API 5L X-52 steel plates cladded with AISI 316L-Si austenitic stainless steel were evaluated. The gas metal arc welding process with pulsed arc (GMAW-P) and controlled arc oscillation were used to join the bimetallic [...] Read more.

The microstructure and mechanical properties of welded joints of API 5L X-52 steel plates cladded with AISI 316L-Si austenitic stainless steel were evaluated. The gas metal arc welding process with pulsed arc (GMAW-P) and controlled arc oscillation were used to join the bimetallic plates. After the root welding pass, buttering with an ERNiCrMo-3 filler wire was performed and multi-pass welding followed using an ER70S-6 electrode. The results obtained by optical and scanning electron microscopy indicated that the shielding atmosphere, welding parameters, and electric arc oscillation enabled good arc stability and proper molten metal transfer from the filler wire to the sidewalls of the joint during welding. Vickers microhardness (HV) and tensile tests were performed for correlating microstructural and mechanical properties. The mixture of ERNiCrMo-3 and ER70S-6 filler materials presented fine interlocked grains with a honeycomb network shape of the Ni–Fe mixture with Ni-rich grain boundaries and a cellular-dendritic and equiaxed solidification. Variation of microhardness at the weld metal (WM) in the middle zone of the bimetallic welded joints (BWJ) is associated with the manipulation of the welding parameters, promoting precipitation of carbides in the austenitic matrix and formation of martensite during solidification of the weld pool and cooling of the WM. The BWJ exhibited a mechanical strength of 380 and 520 MPa for the yield stress and ultimate tensile strength, respectively. These values are close to those of the as-received API 5L X-52 steel. Full article

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20 pages, 3251 KiB

Open AccessArticle

Effect of H₂–CO Ratio on Reduction Disintegration Behavior and Kinetics of Vanadium–Titanium Magnetite Pellets

by Feng Chen, Hao Li, Shuai Wang, Mao Chen, Wenbo Tang, Yufeng Guo, Yuekai Wen and Lingzhi Yang

Metals 2025, 15(8), 823; https://doi.org/10.3390/met15080823 - 23 Jul 2025

Abstract

There are many advantages of the smelting of vanadium–titanium magnetite pellets by hydrogen-based shaft furnace pre-reduction and electric arc furnace process, including high reduction efficiency, low carbon dioxide emission and high recovery of titanium and so on. However, vanadium–titanium magnetite pellets are highly [...] Read more.

There are many advantages of the smelting of vanadium–titanium magnetite pellets by hydrogen-based shaft furnace pre-reduction and electric arc furnace process, including high reduction efficiency, low carbon dioxide emission and high recovery of titanium and so on. However, vanadium–titanium magnetite pellets are highly susceptible to severe reduction disintegration when reduced in the gas-based shaft furnaces. H₂ and CO are the primary reducing gas components in the gas-based shaft furnace process, which significantly influences the reduction behavior of vanadium–titanium magnetite pellets. In this study, the reduction disintegration behavior and reduction kinetics of vanadium–titanium magnetite under mixed H₂–CO atmospheres at low temperatures (450–600 °C) were investigated. The differences in the reduction capacities and rates of H₂ and CO on iron oxides and titanium–iron oxides were revealed, along with their impact on the reduction disintegration behavior of the pellets at low temperatures. At lower temperatures, CO exhibited a greater reducing capability for vanadium–titanium magnetite. As the reduction temperature increased, the reduction capacities of both H₂ and CO improved; however, the reduction capacity of H₂ was more significantly influenced by the temperature. The disparity in the reduction capacities of H₂ and CO for vanadium–titanium magnetite pellets caused an inconsistent expansion rate in different regions of the pellet, increasing internal stress, contributing to a more severe reduction disintegration of vanadium–titanium magnetite pellets in the mixed H₂–CO atmospheres. Full article

(This article belongs to the Special Issue Innovation in Efficient and Sustainable Blast Furnace Ironmaking)

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19 pages, 5702 KiB

Open AccessArticle

Experimental Investigation on Microstructure and Mechanical Properties of Deep Cryogenically Treated Vanadium Alloy Steels

by Dilşad Akgümüş Gök and Rasim İpek

Metals 2025, 15(8), 822; https://doi.org/10.3390/met15080822 - 23 Jul 2025

Abstract

In this study, deep cryogenic treatment (DCT) was applied to cold work tool steels with different vanadium weights (Vanadis 4 and Vanadis 10) for 12, 24 and 36 h, and the changes in their mechanical properties and microstructures were examined. Compression, tensile, hardness, [...] Read more.

In this study, deep cryogenic treatment (DCT) was applied to cold work tool steels with different vanadium weights (Vanadis 4 and Vanadis 10) for 12, 24 and 36 h, and the changes in their mechanical properties and microstructures were examined. Compression, tensile, hardness, SEM–EDS, carbide size, XRD and Rietveld analyses were performed to examine the mechanical and microstructural properties of the cryogenically treated samples. In this study, increasing the cryogenic treatment time and vanadium weight ratio did not have a positive effect on the hardness, and it was determined that the most positive result in terms of tensile and compressive strength was obtained in the V4_DCT-24 sample. The results of this study showed that the cryogenic treatment formed secondary carbides, vanadium carbide (VC) and chromium carbide (Cr₇C₃), in vanadium cold work tool steels and reduced the amount of retained austenite (γ-Fe), transformed into martensite (α’-Fe) structures. Additionally, cryogenically treated Vanadis steels are thought to be usable in the metal processing industry, especially for cutting tools and molds. Full article

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24 pages, 6934 KiB

Open AccessArticle

In Situ High-Resolution Optical Microscopy Survey of the Initial Reactivity of Multiphase ZnAlMgSi Coating on Steel

by Guilherme Adinolfi Colpaert Sartori, Oumayma Gabsi, Tiago Machado Amorim, Viacheslav Shkirskiy and Polina Volovitch

Metals 2025, 15(8), 821; https://doi.org/10.3390/met15080821 - 23 Jul 2025

Abstract

The initial reactivity of a multiphase ZnAlMgSi coating with an Al content > 30 wt.% was studied by in situ reflective microscopy under alternating applied potentials +50 mV/−50 mV vs. open-circuit potential in 5 wt.% NaCl and 5 wt.% Na₂SO₄ [...] Read more.

The initial reactivity of a multiphase ZnAlMgSi coating with an Al content > 30 wt.% was studied by in situ reflective microscopy under alternating applied potentials +50 mV/−50 mV vs. open-circuit potential in 5 wt.% NaCl and 5 wt.% Na₂SO₄ aqueous solutions. In both environments, galvanic coupling between different coating phases and the anodic behavior decreased in the order binary ZnAl > binary Zn/Zn₂Mg > Zn₂Mg > Al(Zn); dendrites were evidenced for the coating exposed alone as well as in galvanic coupling with steel. Contrary to the observations known for Zn-rich ZnAlMg coatings, pure Zn₂Mg was less reactive than the pure ZnAl phase, underlining the importance of the microstructure for reactivity. Si-needles were systematically cathodic, and Al(Zn) dendrites have shown cathodic behavior in some couplings. In the configuration of coupling with steel, corrosion started at the interfaces “binary ZnAl/steel substrate” or “binary ZnAl/Si particle”. The distribution and nature of the corrosion products formed during the experiment were assessed using X-ray microanalysis in scanning electron microscopy and confocal Raman microscopy. In the sulfate environment, a homogenous and stable corrosion product layer formed from the first steps of the degradation; this was in contrast to the chloride environment, where no surface film formed on the dendrites. Full article

(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)

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24 pages, 5129 KiB

Open AccessArticle

On the Solidification and Phase Stability of Re-Bearing High-Entropy Superalloys with Hierarchical Microstructures

by Wei-Che Hsu, Takuma Saito, Mainak Saha, Hideyuki Murakami, Taisuke Sasaki and An-Chou Yeh

Metals 2025, 15(8), 820; https://doi.org/10.3390/met15080820 - 22 Jul 2025

Abstract

This study presents the design and microstructural investigation of a single-crystal (SX) Re-bearing high-entropy superalloy (HESA-X1) featuring a thermally stable γ–γ′–γ hierarchical microstructure. The alloy exhibits FCC γ nanoparticles embedded within L1₂-ordered γ′ precipitates, themselves distributed in a γ matrix, with [...] Read more.

This study presents the design and microstructural investigation of a single-crystal (SX) Re-bearing high-entropy superalloy (HESA-X1) featuring a thermally stable γ–γ′–γ hierarchical microstructure. The alloy exhibits FCC γ nanoparticles embedded within L1₂-ordered γ′ precipitates, themselves distributed in a γ matrix, with the suppression of detrimental topologically close-packed (TCP) phases. To elucidate solidification behavior and phase stability, Scheil–Gulliver and TC-PRISMA simulations were conducted alongside SEM and XRD analyses. Near-atomic scale analysis in 3D using Atom Probe Tomography (APT) revealed pronounced elemental partitioning, with Re strongly segregating to the γ matrix, while Al and Ti were preferentially enriched in the γ′ phase. Notably, Re demonstrated a unique partitioning behavior compared to conventional superalloys, facilitating the formation and stabilization of γ nanoparticles during two-step aging (Ag-2). These γ nanoparticles significantly contribute to improved mechanical properties. Long-term aging (up to 200 h) at 750–850 °C confirmed exceptional phase stability, with minimal coarsening of γ′ and retention of γ nanoparticles. The coarsening rate constant K of γ′ at 750 °C was significantly lower than that of Re-free HESA, confirming the diffusion-suppressing effect of Re. These findings highlight critical roles of Re in enhancing microstructural stability by reducing atomic mobility, enabling the development of next-generation HESAs with superior thermal and mechanical properties for high-temperature applications. Full article

(This article belongs to the Special Issue Solidification and Casting of Metals and Alloys (2nd Edition))

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15 pages, 3017 KiB

Open AccessArticle

Strategies for the Recovery of Tungsten from Wolframite, Scheelite, or Wolframite–Scheelite Mixed Concentrates of Spanish Origin

by Francisco Jose Alguacil, Manuel Alonso, Luis Javier Lozano and Jose Ignacio Robla

Metals 2025, 15(8), 819; https://doi.org/10.3390/met15080819 - 22 Jul 2025

Abstract

Among the strategic materials considered by the EU, tungsten is included; thus, investigations about the recovery of this metal both from natural and recyclable sources are of interest. In this work, we presented an investigation about the recovery of tungsten based on the [...] Read more.

Among the strategic materials considered by the EU, tungsten is included; thus, investigations about the recovery of this metal both from natural and recyclable sources are of interest. In this work, we presented an investigation about the recovery of tungsten based on the treatment of three tungsten-bearing concentrates: scheelite (29% W), wolframite (50% W), and mixed scheelite–wolframite (29% W). All of these come from a cassiterite ore of Spanish origin. The characteristics of each concentrate pave the procedure to be followed in each case. In the case of the wolframite concentrate, the best results were derived from the leaching of the ore with NaOH solutions, whereas the treatment of the scheelite concentrate benefits from an acidic (HCl) leaching. The attack of the mixed concentrate is only possible by a previous roasting step (sodium carbonate and 700–800 °C) followed by a leaching step with water. In the acidic leaching, tungstic acid (H₂WO₄) was obtained, and the alkaline–water leaching produces Na₂WO₄ solutions from which pure synthesized scheelite is precipitated. Full article

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15 pages, 4359 KiB

Open AccessArticle

Phase Transformations During Heat Treatment of a CPM AISI M4 Steel

by Maribel L. Saucedo-Muñoz, Valeria Miranda-Lopez, Felipe Hernandez-Santiago, Carlos Ferreira-Palma and Victor M. Lopez-Hirata

Metals 2025, 15(7), 818; https://doi.org/10.3390/met15070818 - 21 Jul 2025

Abstract

The phase transformations of Crucible Particle Metallurgy (CPM) American Iron and Steel Institute (AISI) M4 steel were studied during heat treatments using a CALPHAD-based method. The calculated results were compared with experimental observations. The optimum austenitizing temperature was determined to be about 1120 [...] Read more.

The phase transformations of Crucible Particle Metallurgy (CPM) American Iron and Steel Institute (AISI) M4 steel were studied during heat treatments using a CALPHAD-based method. The calculated results were compared with experimental observations. The optimum austenitizing temperature was determined to be about 1120 °C using Thermo-Calc software (2024b). Air-cooling and quenching treatments led to the formation of martensite with a hardness of 63–65 Rockwell C (HRC). The annealing treatment promoted the formation of the equilibrium ferrite and carbide phases and resulted in a hardness of 24 HRC. These findings with regard to phases and microconstituents are in agreement with the predictions derived from a Thermo-Calc-calculated time–temperature–transformation diagram at 1120 °C. Additionally, the primary carbides, MC and M₆C, which formed prior to the heat treatment and had a minor influence on the quenched hardness. In contrast, the tempering process primarily led to the formation of fine secondary M₆C carbides, which hardened the tempered martensite to 57 HRC. The present work demonstrates the application of a CALPHAD-based methodology to the design and microstructural analysis of tool steels. Full article

(This article belongs to the Special Issue Advances in Steels: Heat Treatment, Microstructure and Properties)

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27 pages, 3299 KiB

Open AccessArticle

Corrosion Stability and Biological Activity of Anodized cpTi for Dental Application

by Aleksandra S. Popović, Minja Miličić Lazić, Dijana Mitić, Lazar Rakočević, Dragana Jugović, Predrag Živković and Branimir N. Grgur

Metals 2025, 15(7), 817; https://doi.org/10.3390/met15070817 - 21 Jul 2025

Abstract

The anodic oxidation of titanium implants is a practical, cost-effective method to enhance implant success, especially due to rising hypersensitivity concerns. This study investigated the electrochemical behavior, surface characteristics, and biocompatibility of anodized commercially pure titanium (cpTi, grade IV). Anodization is performed on [...] Read more.

The anodic oxidation of titanium implants is a practical, cost-effective method to enhance implant success, especially due to rising hypersensitivity concerns. This study investigated the electrochemical behavior, surface characteristics, and biocompatibility of anodized commercially pure titanium (cpTi, grade IV). Anodization is performed on polished, cleaned cpTi sheet samples in 1 M H₂SO₄ using a constant voltage of 15 V for 15 and 45 min. The color of the oxide layer is evaluated using the CIELab color space, while composition is analyzed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). Additionally, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are performed to identify and monitor the phase transformations of the formed titanium oxides. Corrosion measurements are performed in 9 g L⁻¹ NaCl, pH = 7.4, and show the excellent corrosion stability of the anodized samples in comparison with pure titanium. The biological response is assessed by determining mitochondrial activity and gene expression in human fibroblasts. Anodized surfaces, particularly Ti-45, promote higher mitochondrial activity and the upregulation of adhesion-related genes (N-cadherin and Vimentin) in human gingival fibroblasts, indicating improved biocompatibility and the potential for enhanced early soft tissue integration. Full article

(This article belongs to the Special Issue Feature Paper Collection of “Current Challenges in Corrosion Research" (2nd Edition))

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11 pages, 1293 KiB

Open AccessArticle

DOE-Based Investigation of Microstructural Factors Influencing Residual Stress in Aluminum Alloys

by Nawon Kwak and Eunkyung Lee

Metals 2025, 15(7), 816; https://doi.org/10.3390/met15070816 - 21 Jul 2025

Abstract

Residual stresses generated during the casting process significantly affect the reliability of the final product, making accurate prediction and analysis of these stresses crucial. In particular, to minimize the difference between simulation results and actual measurements, it is essential to develop predictive simulations [...] Read more.

Residual stresses generated during the casting process significantly affect the reliability of the final product, making accurate prediction and analysis of these stresses crucial. In particular, to minimize the difference between simulation results and actual measurements, it is essential to develop predictive simulations that incorporate microstructural characteristics. Therefore, in this study, residual stress prediction simulations were conducted for aluminum components manufactured by high-pressure die casting (HPDC), and measurement locations were selected based on the simulation results. Subsequently, the microstructural characteristics at each location (Si and intermetallic compounds) were quantitatively analyzed, and significant factors affecting residual stress were identified through design of experiments (DOE). As a result, Si sphericity (p-value ≤ 0.05) was observed to be the most significant factor among Si area fraction, IMC area fraction, and Si sphericity, and the residual stress and Si sphericity showed a positive interaction due to the rapid cooling rate and inhomogeneous microstructure distribution. Furthermore, the study demonstrated the effectiveness of DOE in clearly distinguishing the significance of variables with strong interdependencies. Full article

(This article belongs to the Special Issue Mechanical Structure Damage of Metallic Materials)

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14 pages, 2948 KiB

Open AccessArticle

Efficient Flotation Separation of Antimonate Minerals from Quartz Using Sodium Dodecyl Sulfonate as Collector

by Feng Jiang, Pengyuan Wang, Jiaxing Qi, Wei Sun, Yulin Zhou, Weishang Zhao, Shuai He, Yuanjia Luo and Honghu Tang

Metals 2025, 15(7), 815; https://doi.org/10.3390/met15070815 - 21 Jul 2025

Abstract

The efficient separation of antimonate minerals from quartz remains a significant challenge in mineral processing due to their similar surface properties and strong hydrophilicity. This study explored the application of sodium dodecyl sulfonate (SDS) as a selective collector for antimonate–quartz flotation separation. Micro-flotation [...] Read more.

The efficient separation of antimonate minerals from quartz remains a significant challenge in mineral processing due to their similar surface properties and strong hydrophilicity. This study explored the application of sodium dodecyl sulfonate (SDS) as a selective collector for antimonate–quartz flotation separation. Micro-flotation tests demonstrated that SDS achieved optimal recovery of antimonate minerals (90.25%) at pH 8 with a dosage of 70 mg/L, while quartz recovery remained below 10%. Contact angle measurements revealed a significant increase in the hydrophobicity of antimonate minerals after SDS treatment, whereas quartz remained highly hydrophilic. FTIR and XPS analyses confirmed the selective chemisorption of SDS on antimonate mineral surfaces through Sb-O-S bond formation, while negligible adsorption occurred on quartz. Adsorption isotherms further showed the higher SDS uptake on antimonate minerals compared to quartz. These findings collectively demonstrate the effectiveness of SDS as a selective collector for the flotation of antimonate minerals, providing a promising approach to enhancing the recovery of fine antimonate particles. Full article

(This article belongs to the Section Extractive Metallurgy)

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17 pages, 12649 KiB

Open AccessArticle

Microstructure, Mechanical Properties, and Electrochemical Corrosion Behavior of CoCrFeNiNb and CoCrFeNiV High-Entropy Alloys Prepared via Mechanical Alloying and Spark Plasma Sintering

by Yan Zhu, Yiwen Liu, Zhaocang Meng and Jianke Tian

Metals 2025, 15(7), 814; https://doi.org/10.3390/met15070814 - 21 Jul 2025

Abstract

This study investigates the microstructural evolution, mechanical behavior, and electrochemical performance of CoCrFeNiNb and CoCrFeNiV HEAs fabricated via mechanical alloying and spark plasma sintering. Microstructural analyses reveal that the alloys have a face-centered cubic (FCC) matrix with Nb-enriched Laves and V-enriched σ phases. [...] Read more.

This study investigates the microstructural evolution, mechanical behavior, and electrochemical performance of CoCrFeNiNb and CoCrFeNiV HEAs fabricated via mechanical alloying and spark plasma sintering. Microstructural analyses reveal that the alloys have a face-centered cubic (FCC) matrix with Nb-enriched Laves and V-enriched σ phases. The CoCrFeNiNb HEA exhibits superior compressive strength and hardness than CoCrFeNiV due to uniform Laves phases distribution. Fracture surface analysis reveals that at lower sintering temperatures, the fracture is primarily caused by incomplete particle bonding, whereas at higher temperatures, brittle fracture modes dominated via transgranular cracking become predominant. The research results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) show that both alloys exhibited superior electrochemical stability in a 3.5 wt.% NaCl solution compared to the CoCrFeNi base alloy. X-ray photoelectron spectroscopy (XPS) analysis confirms the formation of stable oxide layers (Nb₂O₅ and V₂O₃) on the precipitated phases, acting as protective barriers against chloride ion penetration. The selective oxidation of Nb and V improves the integrity of the passive film, reducing the corrosion rates and enhancing the long-term durability. These findings highlight the critical role of precipitated phases in enhancing the corrosion resistance of HEAs, and emphasize their potential for use in extreme environments. Full article

(This article belongs to the Special Issue High-Entropy Alloys: Processing and Properties)

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14 pages, 2552 KiB

Open AccessArticle

Selective Oxidation Depression of Copper-Activated Sphalerite by H₂O₂ During Chalcopyrite Flotation

by Peiqiang Fan, Xiong Tong, Xian Xie, Qiang Song, Yuanlin Ma, Bin Han, Haitao Fu and Zhiming Lu

Metals 2025, 15(7), 813; https://doi.org/10.3390/met15070813 - 21 Jul 2025

Abstract

Using hydrogen peroxide (H₂O₂), a simple and easily accessible reagent, as a selective depressant, flotation separation experiments of chalcopyrite and copper-activated sphalerite were conducted. The micro-flotation tests of single minerals indicated that H₂O₂ selectively depresses copper-activated [...] Read more.

Using hydrogen peroxide (H₂O₂), a simple and easily accessible reagent, as a selective depressant, flotation separation experiments of chalcopyrite and copper-activated sphalerite were conducted. The micro-flotation tests of single minerals indicated that H₂O₂ selectively depresses copper-activated sphalerite and exerted almost no depressant effect on chalcopyrite. In the flotation tests of artificially mixed minerals, a copper concentrate with a grade of 29.95% and a recovery of 87.30% was obtained, while the zinc content was only 5.76%, demonstrating a significant separation effect. The results of contact angle measurement, Zeta potential measurement, surface adsorption analysis, and XPS analysis suggested that H₂O₂ had a stronger oxidation capacity on the surface of copper-activated sphalerite than chalcopyrite, generating hydrophilic hydroxyl groups on the surface of sphalerite and preventing further adsorption of the collector Z-200 on the surface of sphalerite. Full article

(This article belongs to the Special Issue Advances in Sustainable Utilization of Metals: Recovery and Recycling)

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22 pages, 16125 KiB

Open AccessArticle

Toward an Efficient and Robust Process–Structure Prediction Framework for Filigree L-PBF 316L Stainless Steel Structures

by Yu Qiao, Marius Grad and Aida Nonn

Metals 2025, 15(7), 812; https://doi.org/10.3390/met15070812 - 20 Jul 2025

Abstract

Additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), provides unmatched design flexibility for creating intricate steel structures with minimal post-processing. However, adopting L-PBF for high-performance applications is difficult due to the challenge of predicting microstructure evolution. This is because the process is [...] Read more.

Additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), provides unmatched design flexibility for creating intricate steel structures with minimal post-processing. However, adopting L-PBF for high-performance applications is difficult due to the challenge of predicting microstructure evolution. This is because the process is sensitive to many parameters and has a complex thermal history. Thin-walled geometries present an added challenge because their dimensions often approach the scale of individual grains. Thus, microstructure becomes a critical factor in the overall integrity of the component. This study focuses on applying cellular automata (CA) modeling to establish robust and efficient process–structure relationships in L-PBF of 316L stainless steel. The CA framework simulates solidification-driven grain evolution and texture development across various processing conditions. Model predictions are evaluated against experimental electron backscatter diffraction (EBSD) data, with additional quantitative comparisons based on texture and morphology metrics. The results demonstrate that CA simulations calibrated with relevant process parameters can effectively reproduce key microstructural features, including grain size distributions, aspect ratios, and texture components, observed in thin-walled L-PBF structures. This work highlights the strengths and limitations of CA-based modeling and supports its role in reliably designing and optimizing complex L-PBF components. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing for Metallic Materials and Their Applications (3rd Edition))

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22 pages, 3727 KiB

Open AccessArticle

Johnson–Cook Constitutive Model Parameters Estimation of 22MnB5 Hot Stamping Steel for Automotive Application Produced via the TSCR Process

by Yuxin Song, Yaowen Xu and Gengwei Yang

Metals 2025, 15(7), 811; https://doi.org/10.3390/met15070811 - 20 Jul 2025

Abstract

In the industrial practice of metal forming, the consistent and reasonable characterization of the material behavior under the coupling effect of strain, strain rate, and temperature on the material flow stress is very important for the design and optimization of process parameters. The [...] Read more.

In the industrial practice of metal forming, the consistent and reasonable characterization of the material behavior under the coupling effect of strain, strain rate, and temperature on the material flow stress is very important for the design and optimization of process parameters. The purpose of this work was to establish an appropriate constitutive model to characterize the rheological behavior of a hot-formed steel plate (22MnB5 steel) produced through the TSCR (Thin Slab Casting and Rolling) process under practical deformation temperatures (150–250 °C) and strain rates (0.001–3000 s⁻¹). Subsequently, the material flow behavior was modeled and predicted using the Johnson–Cook flow stress constitutive model. In this study, uniaxial tensile tests were conducted on 22MnB5 steel at room temperature under varying strain rates, along with elevated-temperature tensile tests at different strain rates, to obtain the engineering stress–strain curves and analyze the mechanical properties under various conditions. The results show that during room-temperature tensile testing within the strain rate range of 10⁻³ to 300 s⁻¹, the 22MnB5 steel exhibited overall yield strength and tensile strength of approximately 1500 MPa, and uniform elongation and fracture elongation of about 7% and 12%, respectively. When the strain rate reached 1000–3000 s⁻¹, the yield strength and tensile strength were approximately 2000 MPa, while the uniform elongation and fracture elongation were about 6% and 10%, respectively. Based on the experimental results, a modified Johnson–Cook constitutive model was developed and calibrated. Compared with the original model, the modified Johnson–Cook model exhibited a higher coefficient of determination (R²), indicating improved fitting accuracy. In addition, to predict the material’s damage behavior, three distinct specimen geometries were designed for quasi-static strain rate uniaxial tensile testing at ambient temperature. The Johnson–Cook failure criterion was implemented, with its constitutive parameters calibrated through integrated finite element analysis to establish the damage model. The determined damage parameters from this investigation can be effectively implemented in metal forming simulations, providing valuable predictive capabilities regarding workpiece material performance. Full article

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19 pages, 4839 KiB

Open AccessArticle

Corrosion Inhibition of C38 Steel in 1 M HCl Using Benzoxazole-2-Thione: Electrochemical, SEM-EDX, and Theoretical Studies

by Mohamed Omari, Khalid Bouiti, Said Jebbari, Nabil Lahrache, Ali Barhoumi, Najoua Labjar, Souad El Hajjaji, Mahado Said-Ahmed, Mounim Lebrini, Hamid Nasrellah, Mohammed El Idrissi and Abdessamad Tounsi

Metals 2025, 15(7), 810; https://doi.org/10.3390/met15070810 - 19 Jul 2025

Abstract

This study explores the corrosion inhibition of C38 steel in a 1 M hydrochloric acid (HCl) solution using a novel benzoxazole-2-thione compound. The inhibitor was synthesized and structurally characterized by both ¹H NMR (DMSO-d₆/TMS) and ¹³C NMR spectroscopy. Electrochemical [...] Read more.

This study explores the corrosion inhibition of C38 steel in a 1 M hydrochloric acid (HCl) solution using a novel benzoxazole-2-thione compound. The inhibitor was synthesized and structurally characterized by both ¹H NMR (DMSO-d₆/TMS) and ¹³C NMR spectroscopy. Electrochemical techniques, including Tafel polarization and electrochemical impedance spectroscopy, were employed to evaluate the inhibition performance. The results indicate that the benzoxazole-2-thione significantly reduces the corrosion rate, achieving a maximum inhibition efficiency of 95.25% at a concentration of 10⁻⁴ M. To gain deeper insights into the inhibition mechanism, theoretical methods such as density functional theory, Monte Carlo simulations, and molecular dynamics were applied to investigate the adsorption behavior of the compound on the steel surface. The adsorption process follows the Langmuir isotherm model, suggesting the coexistence of physisorption and chemisorption interactions. Surface morphology and elemental composition analyses using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) confirm the formation of a protective inhibitor film on the steel surface. Full article

(This article belongs to the Special Issue Feature Paper Collection of “Current Challenges in Corrosion Research" (2nd Edition))

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14 pages, 5792 KiB

Open AccessArticle

Weld Formation and Characteristics of Hot-Wire Laser Welding in Aluminum Alloy Narrow-Gap Joints

by Jukkapun Greebmalai, Shun Sadasue, Keita Marumoto, Eakkachai Warinsiriruk and Motomichi Yamamoto

Metals 2025, 15(7), 809; https://doi.org/10.3390/met15070809 - 18 Jul 2025

Abstract

This study joins a 20 mm thick 5000-series aluminum alloy using hot-wire insertion combined with narrow-gap laser welding to evaluate the feasibility and welding characteristics of this technique. The findings indicate that weld formation is primarily influenced by the laser energy density and [...] Read more.

This study joins a 20 mm thick 5000-series aluminum alloy using hot-wire insertion combined with narrow-gap laser welding to evaluate the feasibility and welding characteristics of this technique. The findings indicate that weld formation is primarily influenced by the laser energy density and material deposition rate. A strategy for improving weld beads is introduced incorporating a reoriented laser spot during the final pass on narrow-gap joints. This approach improves penetration and produces defect-free joints. The optimal processing conditions result in complete joint formation with four welding passes. Microstructural analysis reveals that the aluminum matrix morphology evolves according to the local thermal history during welding. Measurements show that the weld region is slightly harder than the base metal, whereas slightly lower hardness is observed at the fusion line and inter-pass boundaries, which correlates with the microstructure result. Full article

(This article belongs to the Special Issue Advanced Laser Welding and Joining of Metallic Materials)

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12 pages, 11870 KiB

Open AccessArticle

Structural, Elastic, Electronic, Magnetic, and Half-Metallic Properties of Full-Heusler Compounds Fe₂LiZ (Z = Ge and Si): A First-Principles Study

by Yufeng Wen, Yanlin Yu, Zhangli Lai and Xianshi Zeng

Metals 2025, 15(7), 808; https://doi.org/10.3390/met15070808 - 18 Jul 2025

Abstract

The structural, elastic, electronic, magnetic, and half-metallic properties of full-Heusler

{Fe}_{2}

LiSi and

{Fe}_{2}

LiGe compounds were investigated using first-principles calculations. Among the studied configurations, the cubic XA structures in the ferromagnetic state for both compounds are the most stable. They [...] Read more.

The structural, elastic, electronic, magnetic, and half-metallic properties of full-Heusler

{Fe}_{2}

LiSi and

{Fe}_{2}

LiGe compounds were investigated using first-principles calculations. Among the studied configurations, the cubic XA structures in the ferromagnetic state for both compounds are the most stable. They exhibit mechanical stability, elastic anisotropy, and ductility. Compared to

{Fe}_{2}

LiGe,

{Fe}_{2}

LiSi demonstrates higher stability, stronger anisotropy, greater brittleness, higher Debye and melting temperatures, and a smaller Grüneisen parameter. Both compounds exhibit metallic majority-spin channels and semiconducting minority-spin channels. At the equilibrium lattice constant,

{Fe}_{2}

LiSi and

{Fe}_{2}

LiGe exhibit half-metallic gaps of 0.141 eV and 0.179 eV, respectively. Both compounds exhibit 100% spin-polarization ratio in specific lattice constant ranges. The total magnetic moment per formula unit (3.000

μ_{B}

) follows the generalized Slater–Pauling rule and depends on Fe atomic magnetic moments. These properties indicate that

{Fe}_{2}

LiSi and

{Fe}_{2}

LiGe hold promise for spintronic applications. Full article

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22 pages, 9679 KiB

Open AccessArticle

Impact of Multiple-Laser Processing on the Low-Cycle Fatigue Behaviour of Laser-Powder Bed Fused AlSi10Mg Alloy

by Arun Prasanth Nagalingam, Erkan Bugra Tureyen, Abdul Haque, Adrian Sharman, Ozgur Poyraz, Evren Yasa and James Hughes

Metals 2025, 15(7), 807; https://doi.org/10.3390/met15070807 - 18 Jul 2025

Abstract

Multi-laser processing is increasingly adopted in laser powder bed fusion (L-PBF) to improve productivity and enable the fabrication of larger components, but its impact on part quality and performance remains a critical concern. This study investigates the microstructure, tensile properties, and fatigue performance [...] Read more.

Multi-laser processing is increasingly adopted in laser powder bed fusion (L-PBF) to improve productivity and enable the fabrication of larger components, but its impact on part quality and performance remains a critical concern. This study investigates the microstructure, tensile properties, and fatigue performance of components fabricated by L-PBF using single- and multiple-laser configurations. Both strategies were evaluated under varying layer thicknesses and gas flow conditions with optimized process parameters. Microstructural analysis revealed defects such as lack-of-fusion, porosity and microcracks in multiple-laser builds with reduced gas flow. However, the density and microhardness results showed negligible differences between single and multiple-laser builds. Tensile testing indicated that single-laser builds exhibited superior strength and ductility, whereas multiple-laser builds demonstrated reduced performance due to localized defects such as lack-of-fusion and microcracks. Low-cycle fatigue testing results showed that optimized multiple-laser strategies could achieve performance comparable to that of single-laser builds while improving productivity. The results also revealed that the gas flow becomes more pronounced with multiple-laser processing, where more spatter is generated due to the interactions of the lasers in a small scan area, and that reduced gas flow leads to fatigue degradation due to increased defect density. The results from this study clearly highlight the importance of gas flow, laser overlap, border optimization, and defect mitigation strategies in producing multiple-laser produced components with mechanical properties and fatigue performance comparable to those of single-laser produced L-PBF components. Full article

(This article belongs to the Special Issue Processing, Microstructure and Properties of Aluminium Alloys)

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17 pages, 6308 KiB

Open AccessArticle

Effect of Heat Treatment on Microstructure and Mechanical Properties of (TiB + TiC) /Ti-6Al-4V Composites Fabricated by Directed Energy Deposition

by Hai Gu, Guoqing Dai, Jie Jiang, Zulei Liang, Jianhua Sun, Jie Zhang and Bin Li

Metals 2025, 15(7), 806; https://doi.org/10.3390/met15070806 - 18 Jul 2025

Abstract

The titanium matrix composites (TMCs) fabricated via Directed Energy Deposition (DED) effectively overcome the issue of coarse columnar grains typically observed in additively manufactured titanium alloys. In this study, systematic annealing heat treatments were applied to in situ (TiB + TiC)/Ti-6Al-4V composites to [...] Read more.

The titanium matrix composites (TMCs) fabricated via Directed Energy Deposition (DED) effectively overcome the issue of coarse columnar grains typically observed in additively manufactured titanium alloys. In this study, systematic annealing heat treatments were applied to in situ (TiB + TiC)/Ti-6Al-4V composites to refine the microstructure and tailor mechanical properties. The results reveal that the plate-like α phase in the as-deposited composites gradually transforms into an equiaxed morphology with increasing annealing temperature and holding time. Notably, when the annealing temperature exceeds 1000 °C, significant coarsening of the TiC phase is observed, while the TiB phase remains morphologically stable. Annealing promotes decomposition of acicular martensite and stress relaxation, leading to a reduction in hardness compared to the as-deposited state. However, the reticulated distribution of the TiB and TiC reinforcement phases contributes to enhanced tensile performance. Specifically, the as-deposited composite achieves a tensile strength of 1109 MPa in the XOY direction, representing a 21.6% improvement over the as-cast counterpart, while maintaining a ductility of 2.47%. These findings demonstrate that post-deposition annealing is an effective strategy to regulate microstructure and achieve a desirable balance between strength and ductility in DED-fabricated titanium matrix composites. Full article

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