Metals

11 pages, 1098 KB

Open AccessArticle

Shrinkage Depression Formation and Yield of Ti–48 at.% Al–2 at.% Nb–2 at.% Cr Ingots Produced by Bottom-Pouring Cold Crucible Induction Melting

by Tomohiro Nishimura, Daisuke Matsuwaka, Hitoshi Ishida, Masami Nohara, Tetsuya Nakamura, Yusuke Yamada and Aoi Shoji

Metals 2026, 16(5), 477; https://doi.org/10.3390/met16050477 (registering DOI) - 28 Apr 2026

Abstract

In this study, a Ti–48 at.% Al–2 at.% Nb–2 at.% Cr alloy was cast by bottom-pouring cold crucible induction melting (CCIM), and the shrinkage depressions formed in ingots during solidification were investigated. Ingots with different heights were produced, and shrinkage depression height and [...] Read more.

In this study, a Ti–48 at.% Al–2 at.% Nb–2 at.% Cr alloy was cast by bottom-pouring cold crucible induction melting (CCIM), and the shrinkage depressions formed in ingots during solidification were investigated. Ingots with different heights were produced, and shrinkage depression height and yield were evaluated based on longitudinal cross-sectional observations. The normalized ingot height ranged from 4 to 25, and the shrinkage depression height increased from 20 mm to 105 mm with increasing ingot height. The yield ranged from 77% to 97% and did not increase monotonically, exhibiting noticeable scatter even among ingots with similar heights. The casting rate ranged from 0.025 kg/s to 0.18 kg/s, and the shrinkage depression height increased with increasing casting rate, whereas no clear correlation was observed between the yield and the casting rate. When the nozzle inner diameter ranged from 2 mm to 5 mm, both the shrinkage depression height and the yield increased, accompanied by scatter. The Reynolds number was evaluated as a parameter representing the average flow condition of the pouring stream; however, shrinkage depression formation could not be uniquely explained by the Reynolds number alone, indicating that melt feeding behavior and heat extraction conditions must also be considered. Full article

(This article belongs to the Special Issue Solidification and Casting of Light Alloys)

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45 pages, 6216 KB

Open AccessReview

Data-Driven and Hybrid Modeling for Metal Fatigue: A Review of Classical Methods, Machine Learning, and Physics-Informed Neural Networks

by Yuzhou Shi, Arko Suryadip Dey and Yazhou Qin

Metals 2026, 16(5), 476; https://doi.org/10.3390/met16050476 - 28 Apr 2026

Abstract

The prediction of metal fatigue life has evolved from classical empirical approaches to advanced, data-driven computational models. However, traditional methods struggle with large data scatter, complex variable-amplitude loading, and the cost of experimental testing. These limitations are particularly pronounced in additively manufactured (AM) [...] Read more.

The prediction of metal fatigue life has evolved from classical empirical approaches to advanced, data-driven computational models. However, traditional methods struggle with large data scatter, complex variable-amplitude loading, and the cost of experimental testing. These limitations are particularly pronounced in additively manufactured (AM) components, which exhibit random porosity and are highly sensitive to process parameters. This review integrates classical fatigue mechanics with modern data-driven methodologies. It evaluates fatigue-life prediction for metallic alloys, welded assemblies, and AM materials. We review classical prediction tools, machine learning (ML) algorithms, deep learning architectures, and physics-informed neural networks (PINNs). ML models capture nonlinear degradation patterns but suffer from limited interpretability (“black-box” behavior) and are unable to extrapolate from small datasets. Embedding governing physical laws into PINNs helps mitigate these limitations. This approach enhances physical consistency, reduces training-data requirements, and strengthens extrapolation capability. In additively manufactured metals, defect location is often a more critical predictor of fatigue failure than defect size or morphology. To address data scarcity, we highlight the use of generative adversarial networks and transfer learning. Integrated models, combined with real-time structural health monitoring data, enable accurate, dynamic digital twins and preemptive fatigue prognosis. Full article

(This article belongs to the Special Issue Fatigue and Fracture Mechanisms of Advanced Metallic Materials)

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18 pages, 2504 KB

Open AccessArticle

Influence of Cutting Parameters on Exit-Side Defects in Abrasive Waterjet Machining of UNS A92024 Aluminum Alloy

by Pedro F. Mayuet Ares, Lucía Rodríguez-Parada, Sergio de la Rosa and Moises Batista

Metals 2026, 16(5), 475; https://doi.org/10.3390/met16050475 - 28 Apr 2026

Abstract

Abrasive waterjet machining (AWJM) is widely used for cutting aerospace aluminum alloys, but exit-side defects associated with jet lag can degrade surface integrity and dimensional accuracy. This work investigates the influence of water pressure, abrasive mass flow rate, and traverse feed rate on [...] Read more.

Abrasive waterjet machining (AWJM) is widely used for cutting aerospace aluminum alloys, but exit-side defects associated with jet lag can degrade surface integrity and dimensional accuracy. This work investigates the influence of water pressure, abrasive mass flow rate, and traverse feed rate on the formation of jet-lag defects at the exit side of cuts in UNS A92024 aluminum alloy plates of 10 mm thickness. A full factorial 3³ experimental design was implemented to manufacture 27 square samples (20 × 20 mm), which were subsequently characterized by optical microscopy at 20× magnification. The semicircular jet-lag defects were quantified using Imaging processing techniques to determine their projected area, and the resulting data were analyzed with multifactor ANOVA and multiple linear regression. The results show that traverse feed rate and water pressure have a statistically significant effect on defect area, with traverse feed rate being the most influential factor, whereas the abrasive mass flow rate plays a secondary role within the investigated range. Combinations of high water pressure and low traverse feed rate led to cleaner cuts with reduced exit-side damage, and contour plots allowed the identification of operational windows that minimize defect formation. The proposed methodology provides a systematic framework for characterizing jet-lag defects in AWJM and can be extended to other alloys, thicknesses, and advanced characterization techniques to support process optimization in industrial applications. Full article

(This article belongs to the Topic Advances in Manufacturing and Mechanics of Materials)

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21 pages, 6011 KB

Open AccessArticle

Informer-Based Prediction of Mold Level Anomalies in Continuous Casting via Temporal and Frequency-Domain Features

by Xin Xin, Meixia Fu, Wei Li, Hongbing Wang, Qu Wang, Yifan Lu, Zhenqian Wang, Yuntian Brian Bai, Tao Gu, Changyuan Yu and Jianquan Wang

Metals 2026, 16(5), 474; https://doi.org/10.3390/met16050474 - 27 Apr 2026

Abstract

The stability of mold level fluctuations (MLFs) is crucial for product quality and process efficiency in continuous casting. Abnormal mold level fluctuations, which are typically associated with multiple factors including stopper rod opening, casting speed, and mold width, are known to lead to [...] Read more.

The stability of mold level fluctuations (MLFs) is crucial for product quality and process efficiency in continuous casting. Abnormal mold level fluctuations, which are typically associated with multiple factors including stopper rod opening, casting speed, and mold width, are known to lead to slab quality defects. In this paper, an Informer-based prediction framework is proposed for the early detection of abnormal MLF. A threshold-based labeling method is developed to quantify the future likelihood and severity of anomalies across different time horizons. Considering the importance of frequency-domain features in mold level prediction, power spectral density (PSD) features are incorporated and smoothed using the exponential moving average (EMA) to enhance predictive performance. Through the integration of temporal and processed spectral features, early indicators of abnormality can be captured, and proactive warnings can be issued. The proposed architecture is validated using approximately 32.5 million data points from a real-world continuous casting process. This approach provides a robust and data-driven solution for predicting and diagnosing abnormal MLF events in continuous casting. Experimental results show that the mean ROC-AUC and PR-AUC reach 0.821 and 0.418, respectively. Full article

(This article belongs to the Section Computation and Simulation on Metals)

17 pages, 7183 KB

Open AccessArticle

The Galvanic Corrosion Behavior of ZCuAl10Fe5Ni5 Coupled with SAF2507 Duplex Stainless Steel in Seawater

by Kunjie Luo, Pu Zhao, Kewei Fang, Wanxiang Zhao, Jiachang Lu, Hongqun Liu, Shuiyong Wang, Mengmeng Zhu and Yanxin Qiao

Metals 2026, 16(5), 473; https://doi.org/10.3390/met16050473 - 27 Apr 2026

Abstract

In nuclear power, marine engineering, and other fields, a matching system composed of duplex steel and copper alloy is a common combination for rotating components in a seawater environment. However, this system is susceptible to galvanic corrosion that seriously threatens its service safety [...] Read more.

In nuclear power, marine engineering, and other fields, a matching system composed of duplex steel and copper alloy is a common combination for rotating components in a seawater environment. However, this system is susceptible to galvanic corrosion that seriously threatens its service safety and service life, with ZCuAl10Fe5Ni5 being the main component corroded. Additionally, current corrosion research on this system has evident gaps. Specifically, the influence of area ratio on galvanic corrosion remains insufficiently understood, and the action mechanism of Cl⁻ on the ZCuAl10Fe5Ni5-based corrosion product film in seawater, as well as the product evolution path, has not been fully revealed, which restricts the development of targeted protection technologies. This study explores the degradation mechanism of ZCuAl10Fe5Ni5 in a specific high-salinity environment (20,000 mg/L Cl⁻), characteristic of nuclear power plant service conditions. The results show that due to the significant electrode potential difference between the SAF2507 duplex steel and ZCuAl10Fe5Ni5 copper alloy, a stable galvanic couple is formed, with ZCuAl10Fe5Ni5 acting as the anode and undergoing dissolution corrosion. When the area ratio of ZCuAl10Fe5Ni5 (anode) to SAF2507 duplex steel (cathode) is 1:50, a significantly stronger galvanic effect is observed. The high concentration of Cl⁻ in seawater can damage the surface of the ZCuAl10Fe5Ni5-based corrosion product film, leading to intensified local corrosion. The ZCuAl10Fe5Ni5-derived corrosion products have a layered structure mainly comprising a mixed system of Cu-Al-Mg oxides/hydroxides, and the corrosion process is accompanied by selective aluminum depletion corrosion. This study provides insight into the corrosion mechanism and key influencing factors of ZCuAl10Fe5Ni5 in the matching system, as well as a theoretical basis and technical support for the design of compatibility metal materials in a seawater environment and the control of corrosion in ZCuAl10Fe5Ni5. Full article

(This article belongs to the Special Issue Surface Modification of Metals for Corrosion Mitigation and Functionalization)

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26 pages, 5835 KB

Open AccessArticle

Efficient Recovery of Vanadium from Vanadium–Titanium Slag (VTS) via Calcification Roasting and Acid Leaching: Process and Mechanism

by Zherui Zhang, Tiantian Liu, Shuming Li, Jinhui Chen, Zhibin Ma, Jie Dang, Ziwen Ying, Guixuan Wu and Shengming Xu

Metals 2026, 16(5), 472; https://doi.org/10.3390/met16050472 - 27 Apr 2026

Abstract

As a strategically important metal, vanadium (V) plays a crucial role in resource security, and its efficient extraction is therefore of great significance. Traditional sodium roasting processes suffer from gaseous pollutant emissions and high costs, while calcification roasting–acid leaching has emerged as an [...] Read more.

As a strategically important metal, vanadium (V) plays a crucial role in resource security, and its efficient extraction is therefore of great significance. Traditional sodium roasting processes suffer from gaseous pollutant emissions and high costs, while calcification roasting–acid leaching has emerged as an alternative due to its environmental friendliness and economic viability. This study focuses on VTS (mainly composed of FeV₂O₄ and Fe₂SiO₄), systematically optimizing the calcification roasting–hydrochloric acid leaching process and investigating its reaction mechanism. By comparing the Gibbs free energy changes of reaction products and the acid leaching process with different additives using DFT calculations, calcium oxide was selected as the optimal calcifying agent. Experimental results show that CaO significantly promotes the transformation of FeV₂O₄ into soluble calcium vanadate and preferentially reacts with SiO₂ to inhibit vanadate encapsulation, creating a structural basis for the selective dissolution of V. Under optimal process conditions, the leaching efficiency of V can reach 94.23%. Furthermore, density functional theory (DFT) calculations substantiate that the inherently weak bonding in Ca₂V₂O₇ facilitates its effortless dissociation during the acid leaching phase. The Douglas hierarchical decision-making method is further adopted for secondary economic potential, and this proposed method has the lowest investment risk. This study provides an experimental and theoretical basis for the efficient and clean extraction of vanadium. Full article

16 pages, 3075 KB

Open AccessArticle

Study on Factors Affecting Efficient Dephosphorization in Hot Metal Pretreatment by the Converter Double-Slag Process

by Jie Wang, Libin Yang, Jiaqing Zeng, Shengtao Qiu and Yong Yang

Metals 2026, 16(5), 471; https://doi.org/10.3390/met16050471 - 27 Apr 2026

Abstract

Given the increasing demand for low-phosphorus molten iron in high-value-added steel production and the rising phosphorus content in raw materials caused by the use of high-phosphorus ores in blast furnaces, the traditional converter single-slag process faces challenges such as high dephosphorization pressure, high [...] Read more.

Given the increasing demand for low-phosphorus molten iron in high-value-added steel production and the rising phosphorus content in raw materials caused by the use of high-phosphorus ores in blast furnaces, the traditional converter single-slag process faces challenges such as high dephosphorization pressure, high slag consumption, and unstable endpoint control. This study systematically investigates the process principles and key influencing factors of the converter double-slag method (MURC process) as an efficient pretreatment technology for molten iron. Through thermodynamic analysis combined with industrial tests, the core process parameters affecting dephosphorization efficiency were identified, including temperature, slag basicity (R), iron oxide (T.Fe) content, and bottom-blowing stirring intensity. The results show that the optimal temperature during the dephosphorization stage is 1350–1400 °C, with slag alkalinity controlled at 1.6–2.0 and T.Fe content maintained at 19–23%. During the decarburization stage, the optimal temperature is 1620–1640 °C, and the final slag alkalinity should be increased to above 3.5. After applying the optimized “low-high-low” oxygen supply pattern and enhanced bottom-blowing stirring (0.04–0.20 Nm³/(t·min)), significant improvements were achieved in industrial practice on 180-t and 60-t converters. Lime consumption was reduced by more than 30%, the average endpoint phosphorus content decreased by approximately 0.005%, the phosphorus removal rate remained stable at above 90%, and the oxygen content in molten steel at the endpoint decreased by 50–100 ppm. This study provides a systematic theoretical basis and practical guidance for efficient and stable dephosphorization using the converter double-slag process. Full article

(This article belongs to the Section Extractive Metallurgy)

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23 pages, 14253 KB

Open AccessArticle

Regulation of the Cavitation, Corrosion, and Cavitation Erosion by the Depth of a Lattice-Array Micro-Pillar Structure in a Saline Solution

by Shuo Yang, Hongxiang Hu, Wentao An, Zitong Wen, Jihang Liu, Zhanwei Zhang, Yanjie Yuan and Zhengbin Wang

Metals 2026, 16(5), 470; https://doi.org/10.3390/met16050470 - 27 Apr 2026

Abstract

This study investigates the influence of the depth of lattice-array micro-pillar surface microstructures on the cavitation erosion (CE) of nickel-aluminum bronze (NAB) in a saline solution using both experimental and simulation methods. Mass-loss measurements, electrochemical tests, and morphological characterizations (SEM, white-light interferometry, EBSD) [...] Read more.

This study investigates the influence of the depth of lattice-array micro-pillar surface microstructures on the cavitation erosion (CE) of nickel-aluminum bronze (NAB) in a saline solution using both experimental and simulation methods. Mass-loss measurements, electrochemical tests, and morphological characterizations (SEM, white-light interferometry, EBSD) were conducted to clarify the erosion, corrosion, and synergistic components. Pressure distribution, vapor volume fraction, and bubble dynamics were revealed by numerical simulation in the cavitation region. Results show that shallow microstructures (0.02 and 0.07 mm depths) significantly reduce the CE by up to 74% compared to the smooth surface. This structure can form a shielding field and suppress the mechanical erosion component. In contrast, deep microstructures (0.18 and 0.22 mm depths) aggravate CE, which is attributed to increased bubble nucleation and localized vapor content, and intensified pressure difference. The pure erosion component dominates the damage, followed by synergistic action, and the pure corrosion component is the least. This trend is independent of the change in the microstructure. These findings extend the knowledge on how to design the microstructure depth to alleviate CE. Full article

(This article belongs to the Special Issue Future Challenges in Electrochemical Corrosion and Protection of Metallic Materials)

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17 pages, 3146 KB

Open AccessArticle

Corrosion Resistance of High-Entropy Alloys in Plateau Salt-Lake Environments

by Shucheng Yang, Jiahao Liu, Shuwen Guo, Jing Zhang, Huaikun Zhu, Zhenjie Ren, Yanting Pan, Lida Che, Zhanfang Wu, Xiangyang Li and Dianchun Ju

Metals 2026, 16(5), 469; https://doi.org/10.3390/met16050469 - 26 Apr 2026

Abstract

The corrosion behavior of high-entropy alloys under cyclic wet–dry conditions simulating the salt-lake atmosphere was investigated. The composition, morphology, and electrochemical properties of the corrosion products formed on the alloy surface after corrosion were systematically analyzed. The results show that in a chloride-containing [...] Read more.

The corrosion behavior of high-entropy alloys under cyclic wet–dry conditions simulating the salt-lake atmosphere was investigated. The composition, morphology, and electrochemical properties of the corrosion products formed on the alloy surface after corrosion were systematically analyzed. The results show that in a chloride-containing environment with alternating temperature and humidity, the Cr-containing oxide passive film formed on the alloy surface effectively inhibits the corrosion process in the early stages. In addition, electrochemical results show that the charge transfer resistance in the MgCl₂ system reaches 4.96 × 10⁵ Ω·cm² at prolonged exposure, which is significantly higher than that in the NaCl system, indicating a lower corrosion rate. However, over time, the passive film undergoes localized rupture due to chloride ion attack and stress, leading to pitting corrosion and expansion toward the substrate. This study reveals the corrosion mechanism of high-entropy alloys in high-altitude salt-lake atmospheric environments and provides crucial insights for material design and performance optimization for their engineering applications in salt-lake scenarios. Full article

17 pages, 58599 KB

Open AccessArticle

Fatigue Crack Growth Behaviour in Welded Joints of Armour Steel

by Mirza Manjgo, Gorazd Lojen, Jure Bernetič, Mihajlo Aranđelović and Tomaž Vuherer

Metals 2026, 16(5), 468; https://doi.org/10.3390/met16050468 - 25 Apr 2026

Abstract

Welded joints are widely recognized as the most critical point in structures made of armour steels due to pronounced thermal effects, microstructural heterogeneity, and the degradation of mechanical and fatigue properties. This study investigates the mechanical properties and fatigue crack growth resistance of [...] Read more.

Welded joints are widely recognized as the most critical point in structures made of armour steels due to pronounced thermal effects, microstructural heterogeneity, and the degradation of mechanical and fatigue properties. This study investigates the mechanical properties and fatigue crack growth resistance of a welded joint produced on SA 500 armour steel, with the aim of preserving the properties of the base material as much as possible. To achieve this, a welding procedure incorporating a high-strength filler wire and optimized welding parameters was applied. Hardness and tensile testing was conducted to evaluate the extent of property degradation caused by welding. The results demonstrate that the applied welding process effectively limited the reduction in hardness and tensile strength, achieving values reasonably close to those of the base material. In addition, fatigue crack growth behaviour was investigated in accordance with ASTM E647, using both the Paris law and the McEvily law. The obtained fatigue crack growth curves and threshold stress intensity factor (ΔK_th) values indicate the nearly identical fatigue behaviour of the base material and the heat-affected zone, confirming the successful preservation of base material fatigue behaviour in the thermally affected zone. Moreover, the weld metal exhibited superior resistance to fatigue crack initiation and growth. Overall, the results confirm that the proposed welding approach provides favourable mechanical and fatigue performance for welded joints in armour steel applications. Full article

(This article belongs to the Special Issue Fracture Mechanics and Failure Analysis of Metallic Materials)

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27 pages, 698 KB

Open AccessReview

An Overview of the Benefits, Drawbacks and Strategies Used for the Fabrication of 316L Stainless Steel and Inconel 625 Functionally Graded Materials Using Wire Arc Additive Manufacturing

by G. Lima Antunes and J. P. Oliveira

Metals 2026, 16(5), 467; https://doi.org/10.3390/met16050467 - 25 Apr 2026

Abstract

Wire arc additive manufacturing (WAAM) is an efficient, low-cost technique for fabricating large-scale metallic components and, in particular, functionally graded materials (FGMs). This review focuses on the fabrication of 316L stainless steel–Inconel 625 FGMs by arc-based WAAM processes, examining Gas Metal Arc Welding [...] Read more.

Wire arc additive manufacturing (WAAM) is an efficient, low-cost technique for fabricating large-scale metallic components and, in particular, functionally graded materials (FGMs). This review focuses on the fabrication of 316L stainless steel–Inconel 625 FGMs by arc-based WAAM processes, examining Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW) in terms of their microstructural outcomes, compositional control strategies, residual stress development and mechanical performance. A critical finding emerging from the reviewed literature is that direct compositional interfaces between 316L and Inconel 625 can yield superior tensile strength and ductility and lower residual stresses compared to smooth gradient strategies, owing to the formation of detrimental secondary phases such as δ-phase, Laves phase and MC carbides at intermediate iron–nickel compositions encountered only during graded builds. The potential of Submerged Arc Additive Manufacturing (SAAM) as a future high-deposition-rate alternative for large-scale FGM fabrication is also discussed. Key challenges, including dilution control, Laves phase formation, residual stress management and the corrosion characterization of the graded region, are identified, together with priority research directions for advancing the industrial adoption of arc-based FGM components. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: “Laser Welding and Additive Manufacturing”)

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20 pages, 2820 KB

Open AccessArticle

Corrosion Resistance of Arc Ion-Plated CrN/CrAlN Multilayer Coatings Before and After Wear Testing: Interface Effects in Marine Environments

by Songjie Zhou, Weilin Chen, Rongjun Yang, Hongwu Liu, Lingxin Zhou, Weizhou Li, Minming Jiang and Xiayun Shu

Metals 2026, 16(5), 466; https://doi.org/10.3390/met16050466 (registering DOI) - 24 Apr 2026

Abstract

In marine service environments, material surfaces inevitably suffer from wear damage, which can compromise the integrity of protective coatings and further affect their corrosion resistance. Therefore, investigating the post-wear corrosion resistance of coatings is of great significance. In this work, single-layer CrN coatings, [...] Read more.

In marine service environments, material surfaces inevitably suffer from wear damage, which can compromise the integrity of protective coatings and further affect their corrosion resistance. Therefore, investigating the post-wear corrosion resistance of coatings is of great significance. In this work, single-layer CrN coatings, CrAlN coatings, and CrN/CrAlN multilayer coatings were deposited on stainless-steel substrates by arc ion plating, and the microstructure, tribological properties, and corrosion behavior before and after wear were systematically investigated. Wear tests were performed under applied loads of 2.5 N and 5 N. The corrosion behavior in the unworn condition and the post-wear corrosion resistance condition was evaluated in a 3.5 wt.% NaCl solution. The results showed that all coatings exhibited a face-centered cubic (FCC) structure, while the CrN/CrAlN multilayer coating possessed the smallest average grain size (13.47 nm). Under applied loads of 2.5 N and 5 N, the CrN/CrAlN multilayer coating exhibited the lowest wear rate, indicating the best wear resistance. In the unworn condition, the CrN/CrAlN multilayer coating showed the lowest corrosion current density (2.74 × 10⁻¹⁰ A/cm²) and the most positive corrosion potential (0.025 V), demonstrating the best corrosion resistance. After wear under a load of 5 N, the CrN/CrAlN multilayer coating retained a low corrosion current density (3.35 × 10⁻¹⁰ A/cm²), in contrast to the marked increases observed for the single-layer coatings. The enhanced performance is considered to be mainly associated with the periodic heterogeneous interfaces in the multilayer structure, which help suppress crack propagation and prolong the penetration path of corrosive media. Full article

(This article belongs to the Section Corrosion and Protection)

17 pages, 1463 KB

Open AccessArticle

Physics-Informed Neural Networks for Process Optimization in Laser Powder Bed Fusion of Inconel 718 Superalloy: A Data-Efficient, Physics-Constrained Machine Learning Framework

by Saurabh Tiwari, Seong Jun Heo and Nokeun Park

Metals 2026, 16(5), 465; https://doi.org/10.3390/met16050465 (registering DOI) - 24 Apr 2026

Abstract

This study aimed to develop and validate a physics-informed neural network (PINN) framework for data-efficient and physically consistent process optimization in the laser powder bed fusion (LPBF) of Inconel 718 (IN718) superalloy. Laser powder bed fusion (LPBF) is widely adopted for fabricating Inconel [...] Read more.

This study aimed to develop and validate a physics-informed neural network (PINN) framework for data-efficient and physically consistent process optimization in the laser powder bed fusion (LPBF) of Inconel 718 (IN718) superalloy. Laser powder bed fusion (LPBF) is widely adopted for fabricating Inconel 718 (IN718) components in aerospace and energy applications; however, navigating its high-dimensional, nonlinear process parameter space remains a central challenge. High-fidelity finite element simulations are computationally prohibitive for extensive parameter sweeps, whereas purely data-driven machine learning (ML) models are limited by data scarcity and unphysical extrapolation behavior. This study presents a physics-informed neural network (PINN) framework that embeds the transient heat conduction equation and Goldak double-ellipsoidal heat source model directly into the neural network training loss, enforcing thermophysical consistency simultaneously with data fidelity. The model was trained on a curated, multi-source dataset of LPBF IN718 parameter combinations drawn from peer-reviewed experimental studies and validated finite element simulation outputs, spanning the laser power (70–400 W), scan speed (200–2000 mm/s), hatch spacing (50–140 µm), and layer thickness (20–50 µm). The PINN predicted the melt pool width, depth, peak temperature, and relative density with mean absolute percentage errors (MAPE) of 3.8%, 4.7%, 3.1%, and 1.9%, respectively, outperforming a baseline artificial neural network (ANN) with an identical architecture. The framework correctly identified the optimal volumetric energy density (VED) window of 55–105 J/mm³, yielding relative densities ≥99.5%, consistent with the published experimental thresholds for IN718. A data efficiency analysis demonstrated that the PINN with 25% training data achieves a performance equivalent to that of the fully trained ANN with 100% data, confirming an approximately four-fold data efficiency improvement attributable to physics-informed regularization, consistent with theoretical predictions. Sensitivity analysis via automatic differentiation confirmed that laser power and scan speed were the dominant parameters (~85% combined variance), which is in agreement with previous studies. This study provides a computationally efficient, interpretable, and physically consistent ML pathway for the accelerated process qualification of IN718 components for aerospace and energy applications. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Materials: Experiments and Modelling)

17 pages, 8023 KB

Open AccessArticle

Effect of H1150M Heat Treatment on Functional Properties of 15-5 PH Stainless Steel Produced by Additive Manufacturing

by Maxim Bassis, Amnon Shirizly and Eli Aghion

Metals 2026, 16(5), 464; https://doi.org/10.3390/met16050464 (registering DOI) - 24 Apr 2026

Abstract

Additive manufacturing (AM) using powder bed fusion (PBF) has been the predominant printing method used over the last decade. The capability of this approach to produce complex parts with high precision has attracted the attention of major industries as a potential tool for [...] Read more.

Additive manufacturing (AM) using powder bed fusion (PBF) has been the predominant printing method used over the last decade. The capability of this approach to produce complex parts with high precision has attracted the attention of major industries as a potential tool for replacing traditional manufacturing technologies. 15-5 PH stainless steel is one of the alloys being studied as a candidate for PBF processes. Its superior strength and corrosion resistance have made it a highly attractive option in numerous industries, including the automotive, nuclear, and petrochemical industries. To enhance the properties of 15-5 PH stainless-steel AM parts following printing, one can use a thermal treatment such as age hardening. However, very little research exists regarding the functional properties of AM parts made from this alloy after heat treatment. This study aims to evaluate the effect of H1150M age hardening heat treatment following printing on the properties of 15-5 PH steel, particularly regarding its mechanical properties and environmental behavior. The microstructure was studied using both optical and electron microscopy, along with X-ray diffraction (XRD) analysis. The mechanical properties were examined by tensile testing and fracture toughness assessment. Corrosion behavior was analyzed in terms of potentiodynamic polarization and using impedance spectroscopy. The results obtained have shown that over-aging caused by H1150M heat treatment has a detrimental effect on the mechanical and environmental behavior of the tested alloy. This was primarily attributed to the formation of an austenitic phase within the inherent martensitic matrix, the generation of brittle phases (mainly carbonitrides of Cr and Nb) and a reduction in grain size. Full article

(This article belongs to the Section Additive Manufacturing)

11 pages, 2865 KB

Open AccessArticle

Effect of Silicon Content on the Performance of Nanostructured Al-Si Alloy Fuels Prepared by Electrical Explosion Method

by Hao Liu, Jie Yao and Shi Yan

Metals 2026, 16(5), 463; https://doi.org/10.3390/met16050463 (registering DOI) - 24 Apr 2026

Abstract

Nano Al-Si alloy fuels with Si contents of 4% and 16% (designated as nAl-4Si, nAl-12Si and nAl-16Si) were prepared by using the electrical explosion method and tested by relevant tests. Subsequently, nAl, nAl-4Si, nAl-12Si, and nAl-16Si were ultrasonically mixed with CuO at stoichiometric [...] Read more.

Nano Al-Si alloy fuels with Si contents of 4% and 16% (designated as nAl-4Si, nAl-12Si and nAl-16Si) were prepared by using the electrical explosion method and tested by relevant tests. Subsequently, nAl, nAl-4Si, nAl-12Si, and nAl-16Si were ultrasonically mixed with CuO at stoichiometric ratios to obtain the corresponding nano-thermite systems. The results indicated that the prepared nano Al-Si alloy fuel consisted of spherical particles with a core–shell structure, wherein the core was composed of aluminum and the shell was composed of silicon. Furthermore, the particle size of the alloy fuel wasn’t significantly affected by the silicon content. However, as the silicon content exceeded the eutectic point, accumulation of silicon and oxygen elements occurs on the surface of nAl-16Si. The actual combustion heat of the nAl-Si alloy fuel rose with the silicon content. The tested combustion heat of nAl-16Si reached 27.24 kJ/g, exceeding that of nAl by 8.43%. The combustion heat of the nAl-Si alloy fuels increased monotonically with the silicon content. TG-DSC tests showed that the ignition temperatures of nAl-4Si and nAl-12Si were lower than those of nAl-16Si and nAl. The onset and peak temperatures of thermal oxidation for the nAl-Si alloy experienced minimal variation with silicon content. However, the oxidation rate progressively decreased with higher silicon content and remained lower than that of pure nAl. Laser ignition tests showed that the peak pressure and pressure rise rate of nAl-4Si/CuO were increased by 8.11 kPa and 24% respectively, compared to nAl/CuO. Therefore, increasing the silicon content could enhance the combustion efficiency of nAl-Si alloy fuels. However, when the silicon content exceeded the eutectic point of Al-Si at 12.6%, the primary silicon formed on the particle surface led to the increase in the solid combustion by-products, thereby weakening the combustion performance. Full article

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18 pages, 11431 KB

Open AccessArticle

Phase Transformation of δ→σ in 24Cr-14Ni Stainless Steels Under Nitrogen Atmospheric Aging Treatment

by Chih-Chun Hsieh and Huei-Sen Wang

Metals 2026, 16(5), 462; https://doi.org/10.3390/met16050462 - 23 Apr 2026

Abstract

This work investigates the δ→σ phase transformation in 24Cr-14Ni stainless steel, specifically focusing on how heat treatment temperature, time, and nitrogen atmospheric ratios (NARs) dictate microstructural stability. Understanding the formation mechanism of the σ phase is critical for alloy design, as it remains [...] Read more.

This work investigates the δ→σ phase transformation in 24Cr-14Ni stainless steel, specifically focusing on how heat treatment temperature, time, and nitrogen atmospheric ratios (NARs) dictate microstructural stability. Understanding the formation mechanism of the σ phase is critical for alloy design, as it remains the most detrimental intermetallic phase in austenitic steels. The results show that δ-ferrite decomposes into σ and secondary γ₂ phases through a cellular eutectoid reaction driven by elemental diffusion. Higher Cr and Si levels stabilize δ-ferrite and promote σ phase precipitation, accelerating the δ→σ transformation. Furthermore, the σ phase exhibits the highest Cr_eq/Ni_eq ratio among all constituent phases. The σ phase fraction is highest with 0 vol.% NAR during 1–8 h of aging and decreases progressively with increasing NARs (20–40 vol.%), reaching a minimum at 80 vol.% under all conditions. JMAK model analysis (n ≈ 0.531, k ≈ 0.905) indicates that σ phase precipitation at 800 °C with 40 vol.% NAR is governed by diffusion-controlled growth with early nucleation site saturation in δ-ferrite. Consequently, rapid σ phase formation occurs, reaching ~21.3% within 1 h. This behavior is attributed to the instability of δ-ferrite and the faster diffusion of Cr and Si compared to austenite. Full article

(This article belongs to the Special Issue Phase Transformations in Metals and Alloys)

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14 pages, 10801 KB

Open AccessArticle

Tailoring Strength and Corrosion Resistance of Al-Zn-Mg-Cu Alloy by Double Aging Processes

by Jianping Huang, Youxuan Ouyang, Yuanyuan Zeng, Huayu Xiao, Juangang Zhao and Qiang Zhang

Metals 2026, 16(5), 461; https://doi.org/10.3390/met16050461 - 23 Apr 2026

Abstract

This study investigated the effects of double aging processes on the tensile properties and salt spray corrosion resistance of an Al-Zn-Mg-Cu alloy. The mechanisms by which microstructural evolution influences these properties were elucidated using tensile testing, salt spray corrosion testing, electrochemical measurements, scanning [...] Read more.

This study investigated the effects of double aging processes on the tensile properties and salt spray corrosion resistance of an Al-Zn-Mg-Cu alloy. The mechanisms by which microstructural evolution influences these properties were elucidated using tensile testing, salt spray corrosion testing, electrochemical measurements, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicate that, under double aging processes, increasing the duration or temperature of either the first- or second-stage aging leads to a slight decrease in tensile strength but a significant improvement in salt spray and electrochemical corrosion resistance. This is attributed to the gradual coarsening of intergranular and grain boundary precipitates, a decrease in their number density, and a widening of the precipitate-free zone (PFZ). Furthermore, the second-stage aging exerts a more pronounced influence on the alloy’s properties and microstructure than the first-stage aging, and their quantitative contributions are systematically distinguished. The alloy treated with the 110 °C/3 h + 155 °C/20 h double aging processes exhibits the optimal overall performance, achieving a better balance between strength and corrosion resistance compared to conventional T6 treatment. Full article

(This article belongs to the Special Issue Recent Advances in High-Performance Alloys and Cermets: Fabrication, Microstructure, and Properties)

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21 pages, 14123 KB

Open AccessArticle

Accelerated Hardening and Corrosion Behavior of Low Cu/Mg Al–Cu–Mg Alloys Modified by Si and Ag

by Guanfeng Huang, Shuai Pan, Chao Dong, Qiliang Chen, Khadija Fnu and Zian Li

Metals 2026, 16(5), 460; https://doi.org/10.3390/met16050460 - 23 Apr 2026

Abstract

The precipitation characteristics and grain-boundary structure of Al–Cu–Mg alloys strongly affect their corrosion behavior, whereas the roles of Si and Ag microalloying in low Cu/Mg ratio systems are not yet fully understood. In this work, the effects of Si and Ag additions on [...] Read more.

The precipitation characteristics and grain-boundary structure of Al–Cu–Mg alloys strongly affect their corrosion behavior, whereas the roles of Si and Ag microalloying in low Cu/Mg ratio systems are not yet fully understood. In this work, the effects of Si and Ag additions on age-hardening response, precipitation characteristics, and corrosion performance were systematically investigated by combining transmission electron microscopy with electrochemical and corrosion measurements. Si addition significantly accelerated the age-hardening kinetics, enabling the alloy to reach a hardness of 147 HV after only 6 h of aging, whereas the base alloy required 24 h to reach a similar level. This accelerated response was accompanied by refined S-phase precipitation and a markedly narrowed precipitation-free zone along grain boundaries. Further Ag addition introduced coherent Ω precipitates and a more complex multi-phase precipitation structure, which increased microstructural heterogeneity. As a result, the Al–Cu–Mg–Si alloy exhibited the lowest corrosion current density and the shallowest corrosion depth, whereas the Al–Cu–Mg–Si–Ag alloy showed deteriorated corrosion resistance. These results indicate that Si microalloying alone can simultaneously accelerate aging and improve corrosion resistance, while further Ag addition enhances precipitation complexity and strengthening potential but increases susceptibility to localized corrosion. Full article

(This article belongs to the Special Issue Advances in Corrosion and Failure Analysis of Metallic Materials)

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25 pages, 10948 KB

Open AccessArticle

Experimental Investigation of Material Characteristics That Can Affect Fatigue Behavior of Ti6Al4V Alloys Produced by Additive Manufacturing SLM and EBM Processes

by Francesco Sordetti, Niki Picco, Marco Pelegatti, Riccardo Toninato, Marco Petruzzi, Federico Milan, Emanuele Avoledo, Alessandro Tognan, Elia Marin, Lorenzo Fedrizzi, Michele Magnan, Enrico Salvati, Michele Pressacco and Alex Lanzutti

Metals 2026, 16(5), 459; https://doi.org/10.3390/met16050459 - 22 Apr 2026

Abstract

Ti alloys are widely used in aerospace and biomedical fields due to their high mechanical properties under severe loading. Interest in additively manufactured Ti6Al4V has increased, but further research is needed to fully characterize their properties. This work compares the effects of surface [...] Read more.

Ti alloys are widely used in aerospace and biomedical fields due to their high mechanical properties under severe loading. Interest in additively manufactured Ti6Al4V has increased, but further research is needed to fully characterize their properties. This work compares the effects of surface properties, internal defects, microstructure, hardness, and Hot Isostatic Pressing (HIP) or Vacuum Heat Treatment (VHT) on the fatigue behavior of Ti6Al4V produced by Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Printing parameters and post-processing were optimized to achieve high density and minimal porosity, providing a solid basis for realistic fatigue comparisons. Samples were characterized in terms of microstructure (optical microscopy and SEM), mechanical properties (hardness mapping), surface texture (confocal microscopy), and internal defects (image-based analysis). Uniaxial fatigue limits were determined by a Dixon-Mood staircase method, and failed specimens were analyzed for fracture surfaces and defect areas. Applied load on flaws was evaluated to identify root causes of fatigue failure. Results showed that fatigue of as-printed samples is governed by surface roughness, while machined specimens are controlled by internal defect size. Machining increased the fatigue limit roughly threefold, and HIP further improved it by 10–20% by reducing internal porosity. In conclusion, with properly optimized melting parameters, both EBM and SLM produce similar mechanical performance at comparable roughness, supporting their use for structural components. Full article

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

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