Metals

17 pages, 1001 KiB

Open AccessArticle

Reducing Mesh Dependency in Dataset Generation for Machine Learning Prediction of Constitutive Parameters in Sheet Metal Forming

by Dário Mitreiro, Pedro A. Prates and António Andrade-Campos

Metals 2025, 15(5), 534; https://doi.org/10.3390/met15050534 (registering DOI) - 10 May 2025

Abstract

Given the extensive use of sheet metal-forming processes in the industry and the constant emergence of new materials, the accurate prediction of material constitutive models and their parameters is extremely important to enhance and optimise these processes. Machine learning techniques have proven to [...] Read more.

Given the extensive use of sheet metal-forming processes in the industry and the constant emergence of new materials, the accurate prediction of material constitutive models and their parameters is extremely important to enhance and optimise these processes. Machine learning techniques have proven to be highly promising for predicting these parameters using data obtained either experimentally or through numerical simulations. However, ML models are often constrained by the limited dataset coverage from numerical simulations, which restricts their predictive capability to specific finite element meshes, leading to potential dependency on the discretisation scheme. To address this challenge, a new approach is proposed that integrates ML with inter-extrapolation of strain data to a grid of points within the specimen domain, expanding the dataset coverage and reducing dependency on discrete mesh points. The current work explores this approach by interpolating and extrapolating manipulated data obtained from a Finite Element Analysis, considering a biaxial tensile test on a cruciform-shaped sample. Models are trained and evaluated for performance and robustness. The results show the high accuracy of the interpolated data, along with the excellent performance metrics and robustness of the trained models, ensuring the successful implementation of this approach. Full article

(This article belongs to the Special Issue Advances in Metal Forming and Plasticity)

► Show Figures

Figure 1

22 pages, 15679 KiB

Open AccessArticle

Achieving Superplasticity in Ultrafine-Grained Mg-9Li Alloy via Dual-Phase Microstructure Optimization

by Jiahao Xu, Xinyue Gong, Wanxiang Zhao, Chao Sun, Guibin Shan, Huan Liu and Dan Song

Metals 2025, 15(5), 533; https://doi.org/10.3390/met15050533 - 9 May 2025

Abstract

In this study, high toughness and superplastic deformability were achieved in Mg-9Li alloys through dual-phase microstructure optimization. Solid solution (SS) and equal channel angular pressing (ECAP) treatments were employed to refine the alloy’s microstructure. The effects of these treatments on room-temperature and low-temperature [...] Read more.

In this study, high toughness and superplastic deformability were achieved in Mg-9Li alloys through dual-phase microstructure optimization. Solid solution (SS) and equal channel angular pressing (ECAP) treatments were employed to refine the alloy’s microstructure. The effects of these treatments on room-temperature and low-temperature high-strain-rate superplasticity were systematically investigated under varying microstructural conditions. Results demonstrate that the SS-ECAP alloy exhibits outstanding superplasticity at room temperature and remarkable high-strain-rate deformation capability, achieving a maximum fracture elongation of 602.1%. Grain refinement and reduced dislocation density promote uniform void nucleation under high strain. Calculations of the strain rate sensitivity index (m-value) and activation energy (Q) reveal that the superplastic behavior in the SS-ECAP state is predominantly governed by grain boundary sliding facilitated by grain boundary diffusion. These findings provide critical insights into advancing the superplastic forming technology of Mg-9Li alloys. Full article

► Show Figures

Figure 1

37 pages, 6043 KiB

Open AccessReview

Analysis of Friction Stir Welding of Aluminum Alloys

by Ikram Feddal, Mohamed Chairi and Guido Di Bella

Metals 2025, 15(5), 532; https://doi.org/10.3390/met15050532 - 9 May 2025

Abstract

Friction Stir Welding (FSW) is a solid-state joining technique that has gained widespread adoption, particularly for aluminum alloys, due to its ability to produce high-quality welds without melting base materials. This comprehensive review focuses on the influence of process parameters on weld characteristics [...] Read more.

Friction Stir Welding (FSW) is a solid-state joining technique that has gained widespread adoption, particularly for aluminum alloys, due to its ability to produce high-quality welds without melting base materials. This comprehensive review focuses on the influence of process parameters on weld characteristics and performance. Compared to conventional fusion welding methods, FSW offers notable advantages, including superior mechanical properties, fewer defects, enhanced corrosion resistance, and lower environmental impact. The review also addresses key challenges such as tool wear, precise process control, and complications arising from welding dissimilar alloys. By synthesizing recent developments and case studies, this work outlines current limitations and proposes future directions for optimizing the FSW process to expand its applicability in critical engineering sectors. Full article

(This article belongs to the Section Welding and Joining)

► Show Figures

Figure 1

27 pages, 937 KiB

Open AccessReview

Use of Hydrogen Peroxide as Oxidizing Agent in Chalcopyrite Leaching: A Review

by Danny J. Flores, Teófilo A. Graber, Alejandro H. Angel-Castillo, Pía C. Hernández and María E. Taboada

Metals 2025, 15(5), 531; https://doi.org/10.3390/met15050531 - 8 May 2025

Abstract

Leaching represents a significant challenge for the mining industry due to its slow and incomplete kinetics under ambient conditions (20 °C, 1 atm) and its increased prevalence in global ore deposits. In this context, the use of hydrogen peroxide (H₂O₂ [...] Read more.

Leaching represents a significant challenge for the mining industry due to its slow and incomplete kinetics under ambient conditions (20 °C, 1 atm) and its increased prevalence in global ore deposits. In this context, the use of hydrogen peroxide (H₂O₂) has proved to be a promising oxidizing agent for improving process efficiency. This article reviews the most recent breakthroughs in the use of H₂O₂ for chalcopyrite leaching, analyzing the experimental conditions that maximize copper extraction, including combinations with novel leachants such as organic systems, inorganic salts, and amino acids. In addition, the main challenges associated with the use of H₂O₂, such as its catalytic decomposition and thermal stability, are highlighted, along with strategies to overcome these limitations. Perspectives and challenges for its application are presented, emphasizing the need for hybrid and optimized approaches to integrate this oxidizing agent in sustainable hydrometallurgical processes. The objective of this paper is to make an exhaustive review of what has been published on chalcopyrite leaching in order to find ways to leach it in large quantities and in a simple way. Full article

(This article belongs to the Special Issue Recent Advances in the Recycling and Reuse of Metallurgical Wastes and By-Products)

► Show Figures

Figure 1

14 pages, 5818 KiB

Open AccessArticle

Impact of Heat Treatment on Microstructure Evolution in Grey Cast Iron EN-GJL-300

by Peter Petruš, Igor Barényi, Jozef Majerík, Michal Krbata, Marcel Kohutiar, Ingrid Kovaříková and Martin Bilka

Metals 2025, 15(5), 530; https://doi.org/10.3390/met15050530 - 8 May 2025

Abstract

This work investigated changes in the microstructure and local mechanical properties after the application of selected heat treatments to EN-GJL-300 grey cast iron. The main goal was to optimize heat treatment to achieve increased mechanical properties and subsequently wear resistance. The heat and [...] Read more.

This work investigated changes in the microstructure and local mechanical properties after the application of selected heat treatments to EN-GJL-300 grey cast iron. The main goal was to optimize heat treatment to achieve increased mechanical properties and subsequently wear resistance. The heat and heat–mechanical treatment were investigated by using a dilatometer as a physical simulator of treatment on real samples. Continuous cooling with three different rates and two other non-continuous treatments (austempering and ausforming) were used to treat the experimental samples. The research was focused on modification of the matrix microstructure, initially pearlitic. No change in the shape or morphology of the graphitic lamellae was required to preserve the damping properties. The results showed that, in terms of the specified conditions, heat treatment with continuous cooling at a rate of 10 °C s⁻¹ appeared to be optimal. This variant showed the presence of bainite and martensite in the microstructure with high hardness measured by nanoindentation as well as the optimal value of general Brinell hardness. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Metallic Materials Under Heat Treatment)

► Show Figures

Figure 1

14 pages, 7353 KiB

Open AccessArticle

Grain Rotation and Deformation Behavior in Cube-Textured Ni Polycrystalline Alloy Studied via In-Situ Tensile Testing and EBSD

by Yaotang Ji, Hongli Suo, Zhen Ma, Baoxu Huang, Jianhua Liu, Lei Wang, Zili Zhang and Qiuliang Wang

Metals 2025, 15(5), 529; https://doi.org/10.3390/met15050529 - 8 May 2025

Abstract

The cube texture in alloys shows deterioration under plastic deformation. To further observe the evolution of orientation in individual grains during deformation, in-situ tensile testing was coupled with electron backscattered diffraction (EBSD). We found that the rotation of an individual grain is not [...] Read more.

The cube texture in alloys shows deterioration under plastic deformation. To further observe the evolution of orientation in individual grains during deformation, in-situ tensile testing was coupled with electron backscattered diffraction (EBSD). We found that the rotation of an individual grain is not only determined by its Schmid factor and size, but also by the condition of the adjacent grains. We demonstrated the interactions between grains using the EBSD data in different models, including the crystal orientation, the kernel average misorientation, the Schmid factor, the inverse pole figure, and the grain reference orientation deviation. A systematic three-factor coupled model involving the Schmid factor, grain size, and neighboring grain states is proposed. Furthermore, the mechanism by which small-sized grains induce the splitting of adjacent larger grains through the pinning effect has not been reported in highly textured polycrystalline materials to date. This characterization allows us to better understand the changes in grain shape and crystal lattice rotation, which can be used to characterize other polycrystalline alloys. Full article

► Show Figures

Figure 1

10 pages, 2090 KiB

Open AccessArticle

Augmenting Fatigue Datasets for Improved Multiaxial Fatigue Strength Prediction with Neural Networks

by Napon Opasanon, Leon Josef Stahr, Lukas Suchy and Alexander Hasse

Metals 2025, 15(5), 528; https://doi.org/10.3390/met15050528 - 7 May 2025

Abstract

Accurate fatigue prediction is essential for ensuring the reliability and durability of engineering systems. Suitable predictive performance was achieved by artificial neural networks trained on the FatLim dataset; however, further improvements are needed due to its small sample size. This study explored the [...] Read more.

Accurate fatigue prediction is essential for ensuring the reliability and durability of engineering systems. Suitable predictive performance was achieved by artificial neural networks trained on the FatLim dataset; however, further improvements are needed due to its small sample size. This study explored the impact of dataset augmentation on model performance by exemplarily expanding the FatLim dataset from 294 to 1732 cases and comparing results against the original dataset. The dataset was augmented by generating additional uniaxial stress scenarios and applying tensor transformations to simulate varied stress orientations. Neural network models were trained separately on the original and expanded datasets, and their predictive performance was evaluated. The results demonstrate that the model trained on the augmented dataset achieved better accuracy, with the mean prediction error decreasing from 0.95% to 0.31% when tested on the original dataset, confirming the effectiveness of dataset expansion in improving fatigue prediction. This research underscores the potential of data augmentation techniques to enhance machine learning models for fatigue analysis. Full article

► Show Figures

Graphical abstract

17 pages, 10899 KiB

Open AccessArticle

Keyhole Depth Prediction in Laser Deep Penetration Welding of Titanium Alloy Based on Spectral Information

by Yunqian Li, Yanfeng Gao, Hao Pan, Donglin Tao and Hua Zhang

Metals 2025, 15(5), 527; https://doi.org/10.3390/met15050527 - 7 May 2025

Abstract

Laser deep penetration welding has been widely applied in industrial fields. However, keyhole depth during the welding process significantly affects the service performance of final products. Based on the spectral signals generated in the laser welding process, this study employs a Long Short-Term [...] Read more.

Laser deep penetration welding has been widely applied in industrial fields. However, keyhole depth during the welding process significantly affects the service performance of final products. Based on the spectral signals generated in the laser welding process, this study employs a Long Short-Term Memory (LSTM) neural network to predict keyhole depth in titanium alloy welding. A coaxial plasma optical information acquisition system is established to collect spectral signals emitted from the welding plasma and analyze the relationship between keyhole depth and plasma spectral features. By analyzing the spectral signals and calculating the plasma temperature, the mapping model between the plasma temperature and keyhole depth is built. The LSTM network prediction results show that the average relative error between the predicted and actual values is 2.31%, which demonstrates that the method proposed in this study has high accuracy for predicting keyhole depth in laser deep penetration welding. Full article

(This article belongs to the Section Welding and Joining)

► Show Figures

Figure 1

14 pages, 9035 KiB

Open AccessArticle

Efficient Regulation of Oxygen Vacancies in β-MnO₂ Nanostructures for High-Loading Zinc-Ion Batteries

by Jian-Chun Wu, Yaoyu Yin, Haitao Zhou, Xicheng Shen, Hongquan Gao, Xiaowei Li, Zhiyong Liu, Yihong Deng and Yanxin Qiao

Metals 2025, 15(5), 526; https://doi.org/10.3390/met15050526 - 7 May 2025

Abstract

Manganese-based oxides, particularly β-MnO₂, have emerged as promising cathode materials for aqueous zinc-ion batteries (ZIBs) due to their high theoretical capacity, low cost, and intrinsic safety. However, their sluggish reaction kinetics, limited active sites, and poor conductivity often lead to suboptimal [...] Read more.

Manganese-based oxides, particularly β-MnO₂, have emerged as promising cathode materials for aqueous zinc-ion batteries (ZIBs) due to their high theoretical capacity, low cost, and intrinsic safety. However, their sluggish reaction kinetics, limited active sites, and poor conductivity often lead to suboptimal electrochemical performance. To address these limitations, we propose a facile ethanol-mediated hydrothermal strategy to engineer rod-like β-MnO₂ nanostructures with tailored oxygen vacancies. By precisely adjusting ethanol addition (3–5 mL) during synthesis, oxygen vacancy concentrations were optimized to enhance electronic conductivity and active site exposure. The experimental results demonstrate that β-MnOx-2-5 synthesized with 5 mL of ethanol delivers an exceptional areal capacity of 4.87 mAh cm⁻² (348 mAh g⁻¹, 469.8 Wh kg⁻¹) at 200 mA cm⁻² under a high mass loading of 14 mg cm⁻². Further, a hybrid electrode combining oxygen-deficient β-MnO₂-x-3 (air-calcined) and structurally stable β-Mn₅O₈-y-3 (Ar-calcined) achieves a retained capacity of 3.9 mAh cm⁻² with stable cycling performance, achieving an optimal equilibrium between high capacity and long-term operational durability. Systematic characterizations (XPS, ESR, XANES, FT-EXAFS) confirm vacancy-induced electronic structure modulation, accelerating ion diffusion and redox kinetics. This scalable vacancy engineering approach, requiring only ethanol dosage control, presents a viable pathway toward industrial-scale ZIB applications. Full article

(This article belongs to the Section Metallic Functional Materials)

► Show Figures

Figure 1

6 pages, 168 KiB

Open AccessEditorial

Challenges and Trends in Additive Manufacturing for Metallic Applications: Toward Optimized Processes and Performance

by Petru Berce and Rǎzvan Pǎcurar

Metals 2025, 15(5), 525; https://doi.org/10.3390/met15050525 - 7 May 2025

Abstract

Additive Manufacturing (AM) for metallic applications continues to redefine how complex, high-performance components are designed and fabricated across a wide range of sectors, including the aerospace, biomedical, and automotive fields, etc [...] Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing and Their Applications (2nd Edition))

22 pages, 11628 KiB

Open AccessReview

Advances in Heavy Metal Extraction Using Organophosphorus Compounds: A Comprehensive Review

by Meriem Essakhraoui, Aziz Boukhair, Fouad Bentiss, Hamid Mazouz, Redouane Beniazza and Nils Haneklaus

Metals 2025, 15(5), 524; https://doi.org/10.3390/met15050524 - 6 May 2025

Abstract

Organophosphorus compounds (OPC) are a large class of organic compounds that provide a wide range of applications, and their importance has grown steadily in recent years. In each category and family, these compounds have similarities and differences. Due to their immense variety, these [...] Read more.

Organophosphorus compounds (OPC) are a large class of organic compounds that provide a wide range of applications, and their importance has grown steadily in recent years. In each category and family, these compounds have similarities and differences. Due to their immense variety, these chemicals have various properties and, therefore, various applications. In fact, various works have been published recently that present the main applications of OPC, especially in metal extraction. Despite their extemsive range of use, optimizing their performance as extractant agents remains a challenge due to their structural variability and sensitivity to process parameters. This review provides a critical analysis of pentavalent OPCs, focusing on how their chemical nature influences heavy metal extraction efficiency. For the first time, we present a novel classification system for OPCs based on phosphorus valency and heteroatom coordination, offering a framework to guide future research. Our findings reveal that the direct coordination of the phosphorus to heteroatoms such as oxygen, sulfur, and nitrogen has a great influence on the physicochemical characteristics of the extractant and the metal extraction efficiency. This observation is in line with Pearson’s Hard and Soft Acids and Bases (HSAB) theory in the sense that it demonstrates that altering the heteroatom alters the metal affinity of the ligand. As a result, these structural modifications can improve the extraction performance by up to 40% for some heavy metals, highlighting the potential for optimized molecular designs to maximize industrial applications. In the future, this work offers a solid foundation for future studies on the rational design of organophosphorus-based extractants. Using HSAB theory and our novel classification system, researchers can rationally design OPCs for their target metal with unparalleled precision. These results have transformative impacts on metal recovery efficiency-intensive sectors like mining, waste recycling, and clean energy technologies. Full article

(This article belongs to the Special Issue Separation, Purification and Extraction of Metals from Primary and Secondary Resources)

► Show Figures

Figure 1

12 pages, 2631 KiB

Open AccessArticle

Alkaloid Extract from Chimarrhis cymosa as a Corrosion Inhibitor for C38 Steel in 1M Hydrochloric Acid: Electrochemical and XPS Studies

by Mahado Said-Ahmed and Mounim Lebrini

Metals 2025, 15(5), 523; https://doi.org/10.3390/met15050523 - 6 May 2025

Abstract

The inhibitory effect of the alkaloid extract from Chimarrhis cymosa on C38 steel corrosion in 1M HCl was examined through electrochemical investigations. An inhibition efficiency of 90% was achieved with 200 mg/L of the alkaloid extract from Chimarrhis cymosa at 25 °C. Potentiodynamic [...] Read more.

The inhibitory effect of the alkaloid extract from Chimarrhis cymosa on C38 steel corrosion in 1M HCl was examined through electrochemical investigations. An inhibition efficiency of 90% was achieved with 200 mg/L of the alkaloid extract from Chimarrhis cymosa at 25 °C. Potentiodynamic polarization revealed that the extract acts as a mixed-type inhibitor. Nyquist plots showed that an increase in the concentration of the alkaloid extract from Chimarrhis cymosa led to an increase in charge-transfer resistance and a decrease in double-layer capacitance, resulting in enhanced inhibition efficiency. The adsorption of inhibitor molecules followed the Langmuir adsorption isotherm. XPS analysis confirmed the formation of an inhibitor layer on the steel surface containing the Chimarrhis cymosa alkaloidic extract. Full article

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

► Show Figures

Graphical abstract

16 pages, 20819 KiB

Open AccessArticle

Production of ZnO Nanofibers from Zinc Galvanizing Flue Dust

by Klaudia Kundráková, Jana Pirošková, Jarmila Trpčevská and Erika Múdra

Metals 2025, 15(5), 522; https://doi.org/10.3390/met15050522 - 6 May 2025

Abstract

This work focuses on the production of ceramic nanofibers from waste materials, which represents a significant contribution to the sustainable use of resources and innovative solutions in the field of nanotechnology. The research builds on existing knowledge of nanofiber production, with a specific [...] Read more.

This work focuses on the production of ceramic nanofibers from waste materials, which represents a significant contribution to the sustainable use of resources and innovative solutions in the field of nanotechnology. The research builds on existing knowledge of nanofiber production, with a specific focus on the use of zinc galvanizing flue dust. The main objective of the study is to explore the possibilities of converting zinc-containing waste materials into ceramic nanofibers, introducing a new direction in nanotechnology. Laboratory experiments involved leaching processes and electrostatic spinning processes of zinc solutions. From the obtained results, it can be concluded that ZnO ceramic nanofibers produced from both synthetic and real solutions exhibit similar fiber structures. Therefore, it can be stated that both acids (HCl and H₂SO₄) are suitable for preparation. Among them, 0.5 M HCl is the most ideal, resulting in oval fibers with a rough and coarse surface, while 0.5 M H₂SO₄ produces fibers with a different morphology in the form of hollow ribbons, which are presumed to have a higher specific surface area. Thus, it can be concluded that the production of ceramic nanofibers from zinc galvanizing flue dust is feasible and effective, with electrostatic spinning proving to be a low-waste technology. The study also examines the influence of contaminants from real waste solutions on the production of ceramic nanofibers and compares their properties with nanofibers obtained from synthetic solutions. Experimental results suggest that contaminants in real solutions did not have a negative impact on the morphology of the prepared ZnO nanofibers. In conclusion, the production of ZnO ceramic nanofibers from waste offers a promising approach for the future development of nanotechnology, combining innovation with sustainability and efficient resource utilization. Full article

► Show Figures

Figure 1

15 pages, 4813 KiB

Open AccessFeature PaperArticle

Double-Flush Riveting for Hybrid Busbar Assembly

by Rui F. V. Sampaio, João P. M. Pragana, Miguel P. Figueiredo, Ivo M. F. Bragança, Carlos M. A. Silva and Paulo A. F. Martins

Metals 2025, 15(5), 521; https://doi.org/10.3390/met15050521 - 5 May 2025

Abstract

This paper explores a novel double-flush riveting process for assembling hybrid busbars made from aluminum and copper sheets. The process involves drilling and forging countersunk holes with controlled geometry in both materials followed by compression of cylindrical rivets into the holes to create [...] Read more.

This paper explores a novel double-flush riveting process for assembling hybrid busbars made from aluminum and copper sheets. The process involves drilling and forging countersunk holes with controlled geometry in both materials followed by compression of cylindrical rivets into the holes to create strong, form- and force-closed mechanical joints. Experimental and numerical analyses are combined to examine material flow, quantify the required forces, and assess the structural integrity of the joints through destructive testing. Additionally, the electrical resistance of these novel joints is evaluated and compared with that of ideal and conventional fastened hybrid busbar joints in order to assess their performance and reliability in real-world electrical service conditions. The results indicate that the novel double-flush riveting process is a viable alternative to other conventional joining processes, such as fastening, delivering good structural integrity and enhanced electrical conductivity for hybrid busbar applications. Full article

(This article belongs to the Special Issue Numerical Modelling of Metal-Forming Processes)

► Show Figures

Figure 1

14 pages, 5864 KiB

Open AccessArticle

Reducing Residual Stresses in Synthetic Cast Iron by Ti Microalloying

by Peter Futas, Janette Brezinová, Miroslav Pástor and Alena Pribulova

Metals 2025, 15(5), 520; https://doi.org/10.3390/met15050520 - 5 May 2025

Abstract

During solidification and cooling of the castings, residual stresses are produced in the material. In technical practice, residual stresses are very important because, in addition to the operational loading, they can lead to material failure and, consequently, to equipment or structural failures. The [...] Read more.

During solidification and cooling of the castings, residual stresses are produced in the material. In technical practice, residual stresses are very important because, in addition to the operational loading, they can lead to material failure and, consequently, to equipment or structural failures. The accurate determination of residual stresses by numerical simulations presents a significant challenge due to the number of variables involved in modelling technological processes. Consequently, in many cases, residual stress levels are typically obtained using experimental measurements. Where possible, these measurements are complemented by monitoring and evaluating parameter changes that occur due to changes in the input conditions. In this paper, findings from experimental measurements of residual stresses in castings made from synthetic cast iron are reported, with a specific focus on the effect of titanium (Ti) microalloying on these residual stress levels. Comparison of the experimental results obtained from castings composed of grey cast iron shows that microalloying with titanium metal effectively reduces the residual stresses while maintaining the same tensile strength and Brinell hardness (HB). This highlights the potential benefits of microalloying in enhancing the benefits and reliability of cast iron materials. Full article

(This article belongs to the Special Issue Recent Advances in Residual Stress Research in Metallic Materials)

► Show Figures

Figure 1

17 pages, 4514 KiB

Open AccessArticle

Statistical Modeling and Characterization of Laser Marking on AISI 301LN Stainless Steel Using Short-Pulsed Fiber Laser

by Mohammad Rezayat, Mojtaba Karamimoghadam, Nicola Contuzzi, Giuseppe Casalino and Antonio Mateo

Metals 2025, 15(5), 519; https://doi.org/10.3390/met15050519 - 4 May 2025

Abstract

This study explores the effects of nanosecond short-pulsed fiber laser processing on AISI 301LN stainless steel, focusing on optimizing surface characteristics through precise parameter control. Using a Design of Experiments (DOE) approach combined with response surface methodology (RSM), the influence of laser power [...] Read more.

This study explores the effects of nanosecond short-pulsed fiber laser processing on AISI 301LN stainless steel, focusing on optimizing surface characteristics through precise parameter control. Using a Design of Experiments (DOE) approach combined with response surface methodology (RSM), the influence of laser power (30–60 W) and the number of laser passes (5–15 times) was systematically investigated. The results demonstrate that increasing the laser power and passes significantly affected the surface properties. The highest surface roughness of 16.8 µm and engraving width of 51 µm were achieved with 60 W power and 15 passes, whereas the lowest roughness of 13.8 µm and width of 35 µm were observed with 30 W power and 5 passes. Wettability measurements revealed an inverse correlation with roughness, with contact angles ranging from 86.4° for rougher surfaces to 92.4° for smoother textures. The findings demonstrate the capability of short-pulsed fiber laser processing to tailor surface properties effectively, with potential applications in manufacturing and surface engineering where controlled roughness and wettability are critical. Full article

► Show Figures

Graphical abstract

24 pages, 23216 KiB

Open AccessArticle

Effect of Aging at Different Temperatures on Microstructure Evolution of 347H Heat-Resistant Steel-Welded Joints

by Jun Xiao, Geng Tian, Di Wang, Kuo Cao and Aimin Zhao

Metals 2025, 15(5), 518; https://doi.org/10.3390/met15050518 - 4 May 2025

Abstract

This study used 347H heat-resistant steel as the base material and systematically investigated the microstructural evolution and second-phase precipitation in typical regions during welding and aging processes. The results showed that the weld metal consisted of austenitic dendrites and inter-dendritic ferrite in a [...] Read more.

This study used 347H heat-resistant steel as the base material and systematically investigated the microstructural evolution and second-phase precipitation in typical regions during welding and aging processes. The results showed that the weld metal consisted of austenitic dendrites and inter-dendritic ferrite in a lath-like form. In the welded samples, the HAZ (Heat-Affected Zone) and BM (Base Material) regions were composed of equiaxed crystals. The microhardness of the HAZ was lower, mainly due to the coarser grain size and fewer second-phase particles. After aging at 700 °C, the hardness of all regions of the welded joint increased significantly due to the precipitation of M₂₃C₆ and MX phases. When the aging temperature increased to above 800 °C, the stability of the M₂₃C₆ phase decreased, and the diffusion rate of Nb in the matrix accelerated, promoting the preferential growth and stable presence of the MX phase. As the MX phase competes with the M₂₃C₆ phase for carbon during its formation, its generation suppresses the further precipitation of the M₂₃C₆ phase. Under 800 °C aging conditions, the γ/δ interface exhibited high interfacial energy, and the Nb content in the ferrite was higher, which facilitated the formation of the MX phase along this interface. As the aging temperature continued to rise, the hardness of the HAZ and BM regions initially increased and then decreased. After aging at 800 °C, the hardness decreased because the M₂₃C₆ phase no longer precipitated. After aging at 900 °C, the hardness of the HAZ and BM regions significantly increased, mainly due to the large precipitation of the MX phase. The hardness of the W (Weld Zone) and FZ (Fusion Zone) regions gradually decreased with the increase in aging temperature, mainly due to the reduction of inter-dendritic ferrite content, coarsening of second-phase particles, weakening of the pinning effect, and grain growth. In the 900 °C aging samples, the MX phase particle size from largest to smallest was as follows: W > HAZ > BM. The Nb-enriched ferrite provided the chemical driving force for the precipitation of the MX phase, while the δ/γ interface provided favorable conditions for its nucleation and growth; thus, the MX phase particles were the largest in the W region. The HAZ region, due to residual stress and smaller grain boundary area, had MX phase particle size second only to the W region. Full article

(This article belongs to the Special Issue Advances in Welding and Joining of Alloys and Steel)

► Show Figures

Graphical abstract

10 pages, 7420 KiB

Open AccessArticle

Effect of Heat Treatment on the Corrosion Behavior of Selective Laser Melted CX Stainless Steel

by Shaoqian Wu, Shuo Wu, Shilong Xing, Tianshu Wang, Jiabin Hou, Yuantao Zhao, Zongan Li and Yanbo Liu

Metals 2025, 15(5), 517; https://doi.org/10.3390/met15050517 - 3 May 2025

Abstract

The effects of different heat treatment regimes on the microstructure and corrosion behavior of selectively laser melted (SLM) Corrax (CX) stainless steel were systematically investigated. Three distinct thermal processing approaches solution treatment (ST), aging treatment (AT), and combined solution aging treatment (ST + [...] Read more.

The effects of different heat treatment regimes on the microstructure and corrosion behavior of selectively laser melted (SLM) Corrax (CX) stainless steel were systematically investigated. Three distinct thermal processing approaches solution treatment (ST), aging treatment (AT), and combined solution aging treatment (ST + AT) were comparatively examined to assess their microstructural evolution and corrosion performance. The results demonstrated that the SLM-processed CX sample initially consisted of martensite and retained austenite. After solution treatment at 900 °C for 0.5 h, microsegregation was eliminated, and the retained austenite fully transformed into martensite. During direct aging at 525 °C for 3 h (AT), a portion of the martensite reverted to austenite, accompanied by grain refinement that reduced the average grain size to 1.79 μm. When the CX was solution-aged at 900 °C for 0.5 h and then 525 °C for 4 h (ST + AT), the retained austenite transformed completely into martensite. The results of potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) revealed that the aged specimen demonstrated comparatively superior corrosion resistance with reduced surface accumulation of corrosion products relative to both ST and ST + AT specimens. The electrochemical test results indicate that the selection of heat treatment parameters has a significant impact on the corrosion resistance of SLM-formed CX samples. Compared to ST and ST + AT, the corrosion performance of AT-treated samples is improved to a certain extent, with the highest E_pit (322 mV) and the largest ΔE (742). The corrosion potential is relatively high (E_corr, −414 mV vs. SCE), and the corrosion current density is relatively low (I_corr, 0.405 μA·cm⁻²). This indicates that the AT samples exhibit good corrosion resistance. Full article

(This article belongs to the Special Issue Mechanical Properties and Corrosion Behavior of Metals after Surface Modification)

► Show Figures

Figure 1

17 pages, 25857 KiB

Open AccessArticle

Dynamic Response of WMoZrNiFe Energetic Structural Material Based on SHPB

by Guiyan Pei, Zhe Peng, Xiaolu Bi, Qingjie Jiao, Rui Liu and Jianxin Nie

Metals 2025, 15(5), 516; https://doi.org/10.3390/met15050516 - 2 May 2025

Abstract

Energetic structural materials (ESMs) are widely studied due to their high energy density, which enhances their potential in various industrial and engineering applications, such as in energy absorption systems, safety devices, and structural components that need to withstand dynamic loading. A high-strength WMoZrNiFe [...] Read more.

Energetic structural materials (ESMs) are widely studied due to their high energy density, which enhances their potential in various industrial and engineering applications, such as in energy absorption systems, safety devices, and structural components that need to withstand dynamic loading. A high-strength WMoZrNiFe energetic structural material was prepared, and its mechanical properties and ignition behavior under dynamic loading were studied. Using the split-Hopkinson pressure bar (SHPB) experimental device, samples with different initial tilt angles of 0°, 30°, and 45° were dynamically loaded. The influence of the sample tilt angle on the ignition threshold was analyzed. The dynamic mechanical properties, failure modes, and ignition threshold based on the energy absorption of the WMoZrNiFe energetic structural material during the dynamic loading process were obtained. The results show that the material has a strain rate effect in the range of 1000 s⁻¹~3000 s⁻¹. The yield strength of the sample with a tilt angle of 0° increased from 1468 MPa to 1837 MPa, that of the sample with a tilt angle of 30° increased from 982 MPa to 1053 MPa, and that of the sample with an inclination angle of 45° increased from 420 MPa to 812 MPa. Through EDS elemental analysis, the ignition reaction mechanism of the WMoZrNiFe energetic structural material under dynamic compression was obtained. The violent reaction of the material occurred after the material fractured, and the active elements reacted with oxygen in the air. Full article

(This article belongs to the Special Issue Properties, Microstructure and Forming of Intermetallics)

► Show Figures

Figure 1

Journal Description

Metals

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Further Information

Guidelines

MDPI Initiatives

Follow MDPI