Metals

22 pages, 20007 KB

Open AccessArticle

A Detail-Preserving Multi-Scale Cascaded Network for Infrared Rotary Kiln Shell Temperature Recognition and Refractory Lining Assessment

by Jie Li, Jianxin He, Hao Liu, Yunhan Hou, Zhiming Dong and Qian Zhang

Metals 2026, 16(6), 597; https://doi.org/10.3390/met16060597 (registering DOI) - 29 May 2026

Abstract

Rotary kiln shell temperature monitoring is essential for metallic shell protection and refractory lining maintenance in high-temperature industrial processes, while smoke, dust, thermal diffusion and non-kiln heat sources make valid shell temperature extraction difficult. This study develops a multi-scale cascaded network with low-resolution [...] Read more.

Rotary kiln shell temperature monitoring is essential for metallic shell protection and refractory lining maintenance in high-temperature industrial processes, while smoke, dust, thermal diffusion and non-kiln heat sources make valid shell temperature extraction difficult. This study develops a multi-scale cascaded network with low-resolution space-to-depth downsampling (MSC-LSTD) for infrared kiln shell segmentation and temperature recognition. Global infrared thermal images and local laser temperature measurements are used to construct a calibrated rotary kiln infrared dataset, and predicted kiln shell masks are mapped to temperature matrices for valid shell temperature analysis. MSC-LSTD achieves 99.82% aAcc, 99.14% mAcc and 97.03% mIoU on the rotary kiln infrared dataset, showing robust segmentation performance under complex thermal interference. The proposed framework provides a practical image-based solution for kiln shell overheating warning and refractory lining degradation assessment. Full article

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

35 pages, 1946 KB

Open AccessReview

Application of Additive Manufacturing Technology in Marine Equipment: A Review

by Hangbin Tang, Zhenyun Ma, Haiwen Ge, Wei Hua and Pengpeng Dong

Metals 2026, 16(6), 596; https://doi.org/10.3390/met16060596 (registering DOI) - 29 May 2026

Abstract

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has emerged as a revolutionary digital near-net-shape manufacturing technology, offering innovative solutions for the design and fabrication of complex, high-performance structures and equipment. This paper reviews the recent advancements and applications of metal AM [...] Read more.

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has emerged as a revolutionary digital near-net-shape manufacturing technology, offering innovative solutions for the design and fabrication of complex, high-performance structures and equipment. This paper reviews the recent advancements and applications of metal AM technologies in the marine sector. Firstly, the principles and characteristics of three most widely adopted metal AM processes in this field are introduced: laser powder bed fusion (L-PBF), directed energy deposition (DED), and wire arc additive manufacturing (WAAM). Subsequently, the application status of metal AM is summarized in four key marine sectors: propulsion systems, underwater vehicle housings and structures, hull structures and shipboard equipment and components, as well as marine equipment repair and emergency support. Building on this, the major challenges for metal AM applications in the marine environment are further discussed, including the fabrication of large-scale components, standardization of materials and processes, integration of smart manufacturing and digital technologies, and sustainability and circular manufacturing. Finally, future trends are projected toward higher efficiency, intelligence, and environmental sustainability. It is indicated that metal AM will fundamentally reshape the manufacturing mode of marine equipment and support its high-performance, low-cost, intelligent and rapid-response development. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing for Metallic Materials and Their Applications (4th Edition))

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44 pages, 4883 KB

Open AccessReview

Gold Recovery Beyond Ores: Sources, Processes, Challenges, and Prospects

by Jovana Djokić, Stefan Nikolić, Stevan Dimitrijević, Shuiping Zhong and Željko Kamberović

Metals 2026, 16(6), 595; https://doi.org/10.3390/met16060595 (registering DOI) - 29 May 2026

Abstract

Gold (Au) is a strategically critical metal whose technological relevance and increasing demand contrast with the long-term decline in primary ore grades. This review discusses gold recovery from primary ores providing the metallurgical and technological baseline for the comparative evaluation of unconventional Au-bearing [...] Read more.

Gold (Au) is a strategically critical metal whose technological relevance and increasing demand contrast with the long-term decline in primary ore grades. This review discusses gold recovery from primary ores providing the metallurgical and technological baseline for the comparative evaluation of unconventional Au-bearing resources. Emphasis is placed on electronic waste and copper anode slimes as highly valuable secondary raw materials containing gold concentrations comparable to, or exceeding, those in natural deposits. The review examines the origin, chemical and mineralogical characteristics, impurity profiles, and processing routes associated with these materials, including conventional and emerging pyro-, hydro-, and biometallurgical approaches. Material-specific constraints, matrix complexity, recovery efficiency, process limitations, and environmental aspects are discussed in relation to process applicability and technological feasibility. Particular attention is given to the differences between geologically constrained primary ores and heterogeneous secondary Au-bearing materials, whose engineered and continuously evolving compositions influence recovery strategies, limiting the direct application of conventional routes to secondary resources. Finally, the review highlights that primary ores remain the dominant source of global Au production, whereas secondary resources currently represent a complementary component, and outlines key challenges and future directions relevant to the broader utilization of these materials. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Hydrometallurgy—4th Edition)

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30 pages, 3196 KB

Open AccessArticle

Analysis of EAF Energy Efficiency Characteristics Based on Industrial Data and Energy Balance

by Hongjin Zhang, Guangsheng Wei, Fuhai Liu, Shenghai Han, Xiaodan Zhong, Jianzhong Wang and Xiaoyun Luo

Metals 2026, 16(6), 594; https://doi.org/10.3390/met16060594 (registering DOI) - 29 May 2026

Abstract

Improving energy efficiency of electric arc furnace (EAF) steelmaking is a key pathway for the iron and steel industry to achieve carbon neutrality. Based on statistical data from 56 industrial EAFs, this study established and validated a comprehensive mass and energy balance model [...] Read more.

Improving energy efficiency of electric arc furnace (EAF) steelmaking is a key pathway for the iron and steel industry to achieve carbon neutrality. Based on statistical data from 56 industrial EAFs, this study established and validated a comprehensive mass and energy balance model with a verification error of less than 5% and systematically quantified the effects of furnace type, furnace capacity, hot metal charging ratio, and scrap preheating on EAF energy efficiency through statistical analysis and scenario simulation. The results show that furnace type is the decisive factor for energy efficiency; Consteel and shaft furnace EAFs with scrap preheating are significantly more efficient than conventional EAFs, with the shaft furnace exhibiting the highest preheating efficiency and best stability. The scale effect of furnace capacity on energy efficiency is weak and fully overshadowed by furnace type. Each 10% increase in hot metal ratio reduces specific power consumption by about 50 kWh/t in conventional furnaces, and the optimal hot metal ratio is 40–50% to balance power consumption and total energy consumption. Scrap preheating saves electricity by recovering physical heat, with each 100 °C temperature increase reducing power consumption by 25 kWh/t; compared with the Consteel process, the shaft furnace process reduces total energy consumption by approximately 14% and increases energy efficiency by 9%. This study provides theoretical support and practical guidance for process optimization in the low-carbon transformation of EAF short-flow steelmaking. Full article

(This article belongs to the Special Issue Novel Insights into Low-Carbon Metallurgical Process Simulation and Optimization)

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22 pages, 25386 KB

Open AccessArticle

Numerical Study of Steel Ball Rolling Using Spiral Discs

by Zbigniew Pater

Metals 2026, 16(6), 593; https://doi.org/10.3390/met16060593 (registering DOI) - 29 May 2026

Abstract

This study proposes a new method for rolling steel balls using spiral discs. The aim of the study was to investigate whether the proposed method could be used to produce balls with a diameter of 63 mm, as well as to determine the [...] Read more.

This study proposes a new method for rolling steel balls using spiral discs. The aim of the study was to investigate whether the proposed method could be used to produce balls with a diameter of 63 mm, as well as to determine the effect of tool geometry and the number of billets on process stability, force, and the energy parameters of the rolling process. Numerical simulations were performed using Forge^® NxT v.4.0. The billet for rolling was made of C60 steel and preheated to 1050 °C. The following cases of ball rolling were simulated: Ball rolling using flat discs with single, double, and triple spiral impressions made on their working surface, and ball rolling using tapered discs for two different configurations of the working system. The rolling process was examined in terms of ball shape, internal defect formation, temperature distribution, as well as force and energy parameters. The results showed that the rolling process conducted using tapered discs and by flat discs with single and double impressions produced correctly shaped balls without internal cracks. It was also found that discs with double impressions were more advantageous than the single-impression ones in terms of energy consumption, while the use of discs with triple spiral impressions led to higher tool load and reduced product quality despite the high efficiency of these discs. The system comprising one disc with an external conical working surface and one disc with an internal conical working surface yielded the best results with the lowest energy consumption and power demand. The findings of this study demonstrate that ball rolling using spiral discs is a promising alternative to standard skew rolling methods. Full article

(This article belongs to the Special Issue Advanced Rolling Technologies of Steels and Alloys)

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21 pages, 2991 KB

Open AccessArticle

Evolution of Corrosion and Mechanical Properties of As-Cast and Solution-Treated Mg-3Zn-0.3Mn-RE Alloys

by Miao Yang, Shuangtian Qin, Xiaohan Yang, Xiaobo Liu and Zhiqiang Cao

Metals 2026, 16(6), 592; https://doi.org/10.3390/met16060592 (registering DOI) - 28 May 2026

Abstract

To develop novel biodegradable magnesium alloys with suitable corrosion resistance and mechanical properties for orthopedic applications, this study investigated the microstructure, mechanical properties, corrosion behavior and wear resistance of as-cast and near-solidus heat-treated Mg-3Zn-0.3Mn alloys with and without Gd/Nd additions (RE-free, 1Gd, 1Gd1Nd). [...] Read more.

To develop novel biodegradable magnesium alloys with suitable corrosion resistance and mechanical properties for orthopedic applications, this study investigated the microstructure, mechanical properties, corrosion behavior and wear resistance of as-cast and near-solidus heat-treated Mg-3Zn-0.3Mn alloys with and without Gd/Nd additions (RE-free, 1Gd, 1Gd1Nd). Rare earth addition refined the grains and transformed the secondary phase from Mg₇Zn₃ to the W-phase (Mg₃RE₂Zn₃). The as-cast 1Gd1Nd alloy showed the finest grains, highest hardness (51.3 HB), best tensile strength (189.38 MPa), lowest corrosion rate (2.80 mm/y) and lowest wear rate (0.614 × 10⁻³ mm³/(N·m)). Near-solidus heat treatment slightly decreased hardness (1–3%) but significantly reduced corrosion rate (e.g., RE-free alloy from 3.61 to 2.78 mm/y) and wear rate. The heat-treated 1Gd1Nd alloy gave the best overall performance: corrosion rate 2.68 mm/y, tensile strength 213.71 MPa and elongation 12.96%. Gd promoted grain refinement and film stability, while Nd stabilized the W-phase, showing a clear combined addition benefit. Notably, the heat-treated RE-free alloy performed similarly to the as-cast 1Gd1Nd alloy, indicating that heat treatment can partially mimic rare earth addition. This work provides a baseline for precursor materials before further processing (e.g., extrusion) toward biodegradable implant applications. Full article

(This article belongs to the Special Issue Effect of Alloying Elements on Oxidation Behavior of Alloys)

25 pages, 4114 KB

Open AccessArticle

Preparation of a Porous Silica-Based Composite Resin Functionalized with Amidoxime Groups for Simultaneous Uranium and Vanadium Extraction from Simulated Seawater

by Jiancheng Jiao, Lifeng Chen, Fengfeng Zhan, Deqian Zeng, Shunyan Ning, Dongqiao He, Jiaxu Zheng, Shaoying Wang, Zhongyuan Zhou, Xufeng Li and Yuezhou Wei

Metals 2026, 16(6), 591; https://doi.org/10.3390/met16060591 (registering DOI) - 28 May 2026

Abstract

The sustainable development of nuclear energy requires a secure long-term uranium supply. Seawater uranium extraction offers a nearly inexhaustible resource; however, its commercialization is limited due to high costs. To improve economic viability, this study proposes a synergistic strategy for simultaneously recovering uranium [...] Read more.

The sustainable development of nuclear energy requires a secure long-term uranium supply. Seawater uranium extraction offers a nearly inexhaustible resource; however, its commercialization is limited due to high costs. To improve economic viability, this study proposes a synergistic strategy for simultaneously recovering uranium and vanadium using amidoxime-based adsorbents, with vanadium as a valuable co-product. Herein, a porous silica-supported poly(amidoxime) adsorbent was synthesized and characterized. The material possesses a well-developed porous structure with a specific surface area of 49.8 m² g⁻¹. Spectroscopic analyses confirmed the successful grafting of amidoxime groups onto the silica framework, whereas X-ray photoelectron spectroscopy revealed that uranium adsorption occurs via coordination with nitrogen and oxygen donor atoms. Batch experiments demonstrated rapid adsorption equilibrium within 2 h and a maximum Langmuir uranium capacity of 48.5 mg g⁻¹ at 45 °C. The adsorbent exhibited high selectivity toward uranium over vanadium and competing ions at near-neutral pH. Dynamic column experiments demonstrated efficient stepwise separation using 0.1 mol L⁻¹ HNO₃ for uranium and a Na₂CO₃–H₂O₂ system for vanadium, even in simulated seawater containing high concentrations of competing ions. Under the controlled model conditions employed, this study demonstrates a promising adsorbent and a feasible co-recovery strategy that may contribute to enhancing the economic feasibility of seawater uranium extraction, warranting further validation in natural seawater. Full article

(This article belongs to the Section Extractive Metallurgy)

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15 pages, 9208 KB

Open AccessArticle

Effect of Heat Treatment on the Mechanical Behavior of Porous Stainless Steel Obtained by L-PBF

by Joel de Jesus, Luis Filipe Borrego, Luis Vilhena, José Martins Ferreira and Ricardo Claudio

Metals 2026, 16(6), 590; https://doi.org/10.3390/met16060590 - 27 May 2026

Abstract

The increasing demand for porous stainless-steel materials produced by selective laser melting (L-PBF) for biomedical implants, filtration systems, heat exchangers, and energy devices has created an urgent need to improve their mechanical performance. Optimizing process parameters and microstructural properties is therefore critical for [...] Read more.

The increasing demand for porous stainless-steel materials produced by selective laser melting (L-PBF) for biomedical implants, filtration systems, heat exchangers, and energy devices has created an urgent need to improve their mechanical performance. Optimizing process parameters and microstructural properties is therefore critical for enhancing the overall functionality and reliability of L-PBF porous stainless-steel structures. This paper studies the effect of an aging heat treatment on the mechanical properties of L-PBF specimens, manufactured with stainless steel Uddeholm Corrax powders. The porosity was selected to be about 3%, based on manufacturer’s experience on the production injection mold inserts, with the ability to drain air. To reach this porosity, a set of manufacturing variables were selected, quantified in terms of VED (Volumetric Energy Density) of 59.01 J/mm³. The analysis of the mechanical behavior was focused on the compressive and flexural strength, dynamic Young’s modulus and the energy dissipation during earlier fatigue loading cycles. This study concluded that the heat treatment produces a negligible effect on dynamic Young’s modulus and increases the bending strength by about 25% and the compressive plateau strength by about 17%. Both specimens’ batches exhibit similar fatigue strain accumulation for cyclic compressive tests. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing for Metallic Materials and Their Applications (4th Edition))

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27 pages, 7710 KB

Open AccessArticle

Carbothermic Reduction and Sulfidation Behavior for Fe–Ni–S Matte Production from Synthetic Saprolitic Nickel Ore

by Chang Ho Jung and Jei-Pil Wang

Metals 2026, 16(6), 589; https://doi.org/10.3390/met16060589 - 26 May 2026

Abstract

This study investigates the production behavior of Fe–Ni–S matte from synthetic nickel ore designed to simulate low-grade saprolitic laterite. The synthetic feed was formulated based on XRF and XRD analyses of magnetically upgraded laterite concentrate. Thermodynamic modeling, including phase stability analysis, Ellingham evaluation, [...] Read more.

This study investigates the production behavior of Fe–Ni–S matte from synthetic nickel ore designed to simulate low-grade saprolitic laterite. The synthetic feed was formulated based on XRF and XRD analyses of magnetically upgraded laterite concentrate. Thermodynamic modeling, including phase stability analysis, Ellingham evaluation, viscosity prediction, and sulfidation equilibria, was employed to define optimal smelting conditions. Carbothermic reduction at 1550 °C enabled selective reduction in NiO and FeO, leading to the formation of Fe–Ni alloy droplets, which subsequently reacted with FeS to produce Fe–Ni–S matte. The carbon ratio played a critical role in controlling FeO content in slag, thereby influencing slag basicity and viscosity. An optimal carbon ratio of 0.2–0.4 mol maintained slag viscosity within the industrially favorable range (2–5 poise) and minimized crucible dissolution. Thermodynamic analysis confirmed that FeS is the only stable sulfide phase at high temperature and dissolves into the Fe–Ni melt, promoting stable matte formation. Under optimized carbon and FeS addition conditions, a maximum nickel recovery of approximately 88% was achieved, attributed to improved slag composition, controlled viscosity, and enhanced matte–slag separation. These results demonstrate that simultaneous carbothermic reduction and sulfidation is an effective route for Fe–Ni–S matte production from saprolite-derived oxide feed. Control of carbon ratio, FeS addition, and Al₂O₃ flux is essential for achieving stable matte formation and efficient metal–slag separation. Full article

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

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Graphical abstract

13 pages, 2865 KB

Open AccessArticle

Reduction Kinetics of Fe³⁺ in the Acid Leachate of Serpentine Neutralization Residue by SO₂

by Rongzheng Yao, Yilai Zhong, Xiyun Yang and Yongqiang Huang

Metals 2026, 16(6), 588; https://doi.org/10.3390/met16060588 - 26 May 2026

Abstract

Neutralization residue results from the hydrometallurgical extraction of magnesium in serpentine, and contains abundant Fe³⁺, Mg²⁺, and Al³⁺. The recovery of these metals involves acid leaching and precipitation. Fe³⁺ often causes co-precipitation and makes separation difficult. [...] Read more.

Neutralization residue results from the hydrometallurgical extraction of magnesium in serpentine, and contains abundant Fe³⁺, Mg²⁺, and Al³⁺. The recovery of these metals involves acid leaching and precipitation. Fe³⁺ often causes co-precipitation and makes separation difficult. The reduction of Fe³⁺ into Fe²⁺ can separate iron from other metals. The reduction kinetics of Fe³⁺ by SO₂ in the acidic leachate from the neutralization residue was studied systematically within the temperature range of 323 to 363 K. The results indicate that SO₂ reduction follows first-order kinetics with respect to Fe³⁺ and 0.71-order with respect to SO₂. SO₂ reduction undergoes dissolution, hydrolysis, complex and reduction. SO₂ dissolution is an exothermic process with ΔH_sol = −42.88 kJ mol⁻¹, the reduction step has an activation energy of 14.52 kJ mol⁻¹. The reduction process is controlled by dissolution and hydrolysis. High pH accelerate the reduction while the co-existing Al³⁺, Mg²⁺ and Ni²⁺ ions inhibit the reduction. A multi-factor-controlled kinetic equation for the reduction of Fe³⁺ by SO₂ was built. This study provides a reference for the establishment of a multi-factor control system dynamics model. Full article

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32 pages, 51996 KB

Open AccessArticle

A Simplified CFD Framework for Parametric Analysis of the Cooling Stage During Aluminothermic Rail Welding: Rapid Welding Process with Short Preheating

by Ravi Govindram Kewalramani, Ingo Riehl, Jan Hantusch and Tobias Fieback

Metals 2026, 16(6), 587; https://doi.org/10.3390/met16060587 - 26 May 2026

Abstract

The quality and integrity of aluminothermic rail welds are strongly governed by the thermal conditions involved during preheating, pouring and cooling stages of the process. In this study, a simplified numerical framework is presented, based on the finite volume method and implemented in [...] Read more.

The quality and integrity of aluminothermic rail welds are strongly governed by the thermal conditions involved during preheating, pouring and cooling stages of the process. In this study, a simplified numerical framework is presented, based on the finite volume method and implemented in the open-source software OpenFOAM^® version 7, to predict the heat transfer and solidification processes. Within this framework, the preheating stage is simulated by employing a heat flux profile derived from experimental measurements, while the mould filling stage is neglected under the assumption of instantaneous pouring of the molten metal. The steel–slag multiphase system is treated using the Volume of Fluid method, whereas melting and solidification are captured using the enthalpy-porosity approach on a fixed Eulerian grid. The numerical framework is validated for a rapid welding process with short preheating procedure, consistent with typical industrial practice for rail welding. The predicted temperature histories during the preheating stage show sufficiently good agreement with the experimental measurements. Subsequently, the cooling stage is validated for a molten metal temperature of 2200

^{\circ} C

(≈

2200 + 273

K

). The predicted width of the fusion zone is compared with experimental data, showing reasonably good agreement in the railhead region, while an underestimation is observed in the rail web and rail foot regions. Furthermore, a systematic parametric investigation is conducted by varying two key process parameters, namely the molten metal temperature examined at four distinct levels ranging from 1800

^{\circ} C

(≈

1800 + 273

K

) to 2400

^{\circ} C

(≈

2400 + 273

K

), and the active preheating duration, varied across six values ranging from 90

s

(

90 / 60

\min

)– 390

s

(

390 / 60

\min

), in order to assess their influence on the cooling stage. The numerical results provide detailed insight into the temporal evolution of the thermal field and its influence on the formation and extent of the fusion zone and heat-affected zone. The results demonstrate that, despite simplifications, the model captures the dominant thermal phenomena of the process and offers a computationally efficient tool for parameter studies and process optimisation. Full article

(This article belongs to the Section Welding and Joining)

19 pages, 5011 KB

Open AccessArticle

Study of Fatigue Crack Growth in Superalloy Based on Acoustic Emission K-Entropy

by Ting Jing, Yang Yu and Qiang Liu

Metals 2026, 16(6), 586; https://doi.org/10.3390/met16060586 - 26 May 2026

Abstract

Acoustic emission (AE) technology was used to monitor the fatigue crack growth process of superalloy. The analysis results show that both the cumulative values and the K-entropy values of AE parameters have good correspondences with the three stages described by fracture mechanics, which [...] Read more.

Acoustic emission (AE) technology was used to monitor the fatigue crack growth process of superalloy. The analysis results show that both the cumulative values and the K-entropy values of AE parameters have good correspondences with the three stages described by fracture mechanics, which makes it possible to characterize the process of fatigue crack growth. Since K-entropy is more sensitive to changes in fatigue state, the turning points between the second stage and the third stage are earlier than those defined by fracture mechanics, indicating that it has an early warning capability. The K-entropy of AE parameter was first proposed to represent the growth rate of fatigue crack. This method not only effectively decreased the large dispersion of change rate of AE parameters but also ensured the similarity with the fatigue crack growth rate, thereby optimizing the characterization of fatigue crack growth. Full article

(This article belongs to the Section Metal Failure Analysis)

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19 pages, 3206 KB

Open AccessArticle

Finite Element Simulation and Experimental Validation of Induction Heating Coil Design for TiAl Blade

by Yunchuan Zhang, Puwei Dang and Huiyu Xu

Metals 2026, 16(6), 585; https://doi.org/10.3390/met16060585 - 26 May 2026

Abstract

To improve temperature uniformity and reduce thermal stress-induced cracking during laser directed energy deposition (laser DED) repair of TiAl blades, this study proposes a refined induction heating coil design based on coupled electromagnetic-thermal finite element simulation. A temperature-dependent model of the induction heating [...] Read more.

To improve temperature uniformity and reduce thermal stress-induced cracking during laser directed energy deposition (laser DED) repair of TiAl blades, this study proposes a refined induction heating coil design based on coupled electromagnetic-thermal finite element simulation. A temperature-dependent model of the induction heating process for a cast 45XD TiAl blade was established and used to compare circular and elliptical coil cross-sectional shapes. The elliptical coil reduced the magnetic field concentration at the leading and trailing edges and decreased the maximum temperature difference across the blade cross-section to below 100 K, thereby improving transverse temperature uniformity. To further improve the temperature distribution along the blade length, a variable-pitch solenoid coil with sparse turns in the middle and dense turns near both ends was designed. This arrangement improved the balance between local heat generation and heat dissipation and reduced the temperature variation within the central 10 cm region of the blade to about 10 K. Experimental validation showed engineering-level agreement with the simulation results, and the blade body was stably maintained at 1020–1030 K, satisfying the preheating requirement for laser DED repair of TiAl blades within the tested design set. Full article

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

14 pages, 9424 KB

Open AccessArticle

Dependence of Intragranular Orientation Gradients on Grain Orientation in Cold-Rolled Fe-3%Si Steel

by Xi Chen, Guojin Zhang, Songtao Chang, Yuhui Sha and Fang Zhang

Metals 2026, 16(6), 584; https://doi.org/10.3390/met16060584 - 26 May 2026

Abstract

Intragranular orientation gradients play a critical role in deformation and recrystallization texture evolution of silicon steel. In this study, the dependence of intragranular orientation gradients on grain orientation in a cold-rolled Fe-3%Si alloy was systematically investigated through electron backscatter diffraction (EBSD), complemented by [...] Read more.

Intragranular orientation gradients play a critical role in deformation and recrystallization texture evolution of silicon steel. In this study, the dependence of intragranular orientation gradients on grain orientation in a cold-rolled Fe-3%Si alloy was systematically investigated through electron backscatter diffraction (EBSD), complemented by a rate-dependent crystal plasticity model, incorporating grain boundary resistance. A comparative assessment of intragranular orientation gradients in the grain core and grain boundary regions revealed that they are markedly sensitive to grain orientation, with the grain boundary region exhibiting a higher orientation gradient than the grain core. The formation of intragranular orientation gradients is governed by the orientation stability during plastic deformation: stable convergent α (<110>//RD, rolling direction) and γ (<111>//ND, normal direction) orientations develop lower orientation gradients, whereas grains with unstable divergent λ (<001>//ND) orientations exhibit higher orientation gradients. Furthermore, intergranular interactions during rolling reduce orientation stability near grain boundaries, thereby promoting higher orientation gradients in the grain boundary region compared to the grain core. Full article

(This article belongs to the Special Issue Rolling and Forming of Alloys and Steels)

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17 pages, 4888 KB

Open AccessArticle

Investigation of Bubble Size and Spatial Distribution in a Continuous Casting Mold Considering Coalescence and Breakup

by Qingrui Lai, Zhiguo Luo, Yongjie Zhang and Zongshu Zou

Metals 2026, 16(6), 583; https://doi.org/10.3390/met16060583 - 26 May 2026

Abstract

In a steel continuous casting mold, argon bubbles injected through the submerged entry nozzle undergo transport, coalescence, and turbulent breakup, producing a polydisperse bubble swarm that affects flow stability and defect formation. In this study, an Euler–Lagrange model coupled with bubble collision coalescence [...] Read more.

In a steel continuous casting mold, argon bubbles injected through the submerged entry nozzle undergo transport, coalescence, and turbulent breakup, producing a polydisperse bubble swarm that affects flow stability and defect formation. In this study, an Euler–Lagrange model coupled with bubble collision coalescence and turbulence-induced breakup sub-models was established and validated using water model observations. Three daughter-bubble volume distribution models were compared in terms of bubble-cloud morphology, number-fraction distribution, and median-diameter evolution at different gas flow rates. For the median bubble diameter at different gas flow rates, the M-type model gives the lowest mean absolute error of 0.0349 mm. Large bubbles with diameters greater than 2.5 mm accounted for about 4% of the total number and were mainly concentrated near the SEN, whereas small bubbles with diameters of 1.0–1.5 mm accounted for about 60% and were dispersed throughout the upper recirculation region. Mechanism analysis further shows that bubble transport is drag-dominated in the high-velocity jet region, while buoyancy becomes more important in weaker flow regions; turbulent breakup is localized mainly in high-dissipation regions. Full article

(This article belongs to the Special Issue Advanced Simulation and Modeling Technologies of Metallurgical Processes—2nd Edition)

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18 pages, 9586 KB

Open AccessArticle

Fracture Failure Analysis of U75V Pearlitic Rail on Sharp Radius Curved Track

by Junjie Fei, Hongfang Qi, Bei Yuan, Minbiao Wan and Linlang Zhang

Metals 2026, 16(6), 582; https://doi.org/10.3390/met16060582 - 26 May 2026

Abstract

A transverse fracture occurred in U75V pearlitic rail after 5 months of service on a sharp radius curved track of mixed passenger-freight railway. Systematic tests including chemical composition analysis, mechanical properties testing, macroscopic fracture inspection, metallographic observation and microscopic morphology characterization were conducted [...] Read more.

A transverse fracture occurred in U75V pearlitic rail after 5 months of service on a sharp radius curved track of mixed passenger-freight railway. Systematic tests including chemical composition analysis, mechanical properties testing, macroscopic fracture inspection, metallographic observation and microscopic morphology characterization were conducted on the failed rail sample. The results indicate that the rail base metal has qualified metallurgical quality. Its chemical composition, fundamental mechanical properties and microstructure fully meet the requirements of Chinese railway standard TB/T 2344.1-2020. The failure mode is identified as instantaneous brittle fracture. Severe mechanical extrusion and impact cause prominent plastic deformation on the rail foot, leading to surface plastic flow and further triggering micro-crack initiation. Under continuous cyclic stress induced by train loads, the micro-crack tips undergo repeated tearing and closing. Severe stress concentration accelerates the formation of transgranular cracks, which propagate rapidly and unstably toward the rail interior, eventually resulting in catastrophic transverse fracture. Standardized procedures in rail transportation, hoisting and laying are essential to avoid mechanical damage, while regular line inspection and timely replacement of damaged rails should be strictly enforced. Full article

(This article belongs to the Section Metal Failure Analysis)

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21 pages, 6591 KB

Open AccessArticle

Optimization of Heat Treatment Parameters for Austenitic Stainless Steel Cladding Using the Taguchi Method

by Wissal Yangui, Rami Ghorbel, Farid Takali, Wafa Naifar, Ahmed Ktari, Khaled Elleuch and Nader Haddar

Metals 2026, 16(6), 581; https://doi.org/10.3390/met16060581 - 26 May 2026

Abstract

Hot-rolled A283 Gr C carbon steel/A240 TP 316L stainless steel-clad plates are widely used in structural applications. However, the hot-rolling process introduces residual stresses and microstructural heterogeneities near the interface, which can adversely affect mechanical performance. This study aims to optimize stress-relief annealing [...] Read more.

Hot-rolled A283 Gr C carbon steel/A240 TP 316L stainless steel-clad plates are widely used in structural applications. However, the hot-rolling process introduces residual stresses and microstructural heterogeneities near the interface, which can adversely affect mechanical performance. This study aims to optimize stress-relief annealing parameters for hot-rolled A283 Gr C/A240 TP 316L-clad steel in order to enhance toughness while preserving microstructural integrity. A Taguchi experimental design based on an L9 orthogonal array was employed to evaluate the effects of holding temperature, holding time, and heating/cooling velocity on Charpy impact toughness. Signal-to-noise (S/N) ratio analysis and ANOVA were used to identify the most influential parameters. Microstructural observations, microhardness profiling, and Charpy impact testing were conducted before and after heat treatment. The results indicate that stress-relief annealing does not alter the base microstructures of either the carbon steel substrate or the austenitic stainless steel-clad layer, nor does it induce carbide precipitation or secondary phase formation in the A240 TP 316L stainless steel. A noticeable reduction in the thickness of the decarburized ferrite zone near the interface was observed, suggesting improved interfacial stability. Microhardness measurements revealed a moderate decrease in hardness near the interface, accompanied by a significant increase in Charpy impact toughness under optimized conditions. ANOVA results show that holding temperature is the dominant factor influencing toughness, followed by heating/cooling velocity, while holding time has a minor effect. The optimal stress-relief annealing conditions were identified as 550 °C for 45 min, with a heating/cooling velocity of 100 °C/h. These findings demonstrate that the Taguchi method is an effective approach for optimizing heat treatment parameters and improving the mechanical integrity of hot-rolled stainless steel-clad plates. Full article

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27 pages, 6916 KB

Open AccessArticle

Effect of Microstructure Development on the Corrosion Behavior of EN AW-5083 in As-Cast and Homogenized Conditions

by Natalija Dolić, Zdenka Zovko Brodarac, Franjo Kozina and Anita Begić Hadžipašić

Metals 2026, 16(6), 580; https://doi.org/10.3390/met16060580 - 25 May 2026

Abstract

The corrosion behavior of the EN AW-5083 alloy was investigated due to its widespread use in marine and transportation applications. The study examined the influence of microstructure development on corrosion behavior in both as-cast and homogenized conditions. Thermodynamic calculations, differential scanning calorimetry, and [...] Read more.

The corrosion behavior of the EN AW-5083 alloy was investigated due to its widespread use in marine and transportation applications. The study examined the influence of microstructure development on corrosion behavior in both as-cast and homogenized conditions. Thermodynamic calculations, differential scanning calorimetry, and metallographic characterization were used to analyze solidification and microstructure development, while electrochemical testing was applied to evaluate corrosion resistance in a solution simulating severe outdoor exposure conditions, primarily marine, industrial, and transportation environments. The results show that the as-cast microstructure contains a heterogeneous distribution of anodic and cathodic intermetallic phases, which promotes localized corrosion. Homogenization at 520 °C led to the dissolution of the Al₈Mg₅ (β) phase, resulting in reduced sensitization effects and slightly improved corrosion resistance. However, high corrosion rates were observed in both metallurgical conditions, indicating limited resistance under the applied testing conditions. The study confirms that microstructural modification through homogenization influences corrosion mechanisms in EN AW-5083. Full article

(This article belongs to the Special Issue New Insights into Aluminum Alloys: Processing, Microstructure and Mechanical Properties)

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18 pages, 3137 KB

Open AccessArticle

Study on Efficient and High-Precision Modeling of 3D Temperature Field in Continuous Casting Round Billets Based on Hybrid Coordinate System and Equal-Area Grid

by Xinqiang Li, Shengdun Zhao, Mingjun Qiu, Tianlong Lian, Yongfei Wang, Jing Zeng, Shaobo Ma, Xiaochen Du and Shuqin Fan

Metals 2026, 16(6), 579; https://doi.org/10.3390/met16060579 - 25 May 2026

Abstract

Aiming at the challenging issue of nonlinear coupling control between cooling intensity and solidification rate in the secondary cooling zone of round billet continuous casting, this study proposes an efficient 3D temperature field modeling method that integrates hybrid coordinate systems with equal-area meshing. [...] Read more.

Aiming at the challenging issue of nonlinear coupling control between cooling intensity and solidification rate in the secondary cooling zone of round billet continuous casting, this study proposes an efficient 3D temperature field modeling method that integrates hybrid coordinate systems with equal-area meshing. The model is applicable to the temperature range of 800–1520 °C during the continuous casting process. With the modeling strategies of constructing an r-θ-z hybrid coordinate system and designing a dynamic equal-area meshing method, and combined with a topological structure optimization algorithm, the geometric adaptability and numerical stability of the model are significantly improved. Based on this, an explicit-semi-implicit dual-mode finite difference solution model is developed, where the explicit scheme meets real-time online calculation requirements, and the semi-implicit scheme combined with preconditioned Gauss–Seidel iteration enables high-precision offline simulation. Furthermore, a boundary condition model incorporating adaptive mold heat flux correction and multi-mechanism heat transfer in the secondary cooling zone is established. Based on Microsoft Visual Studio 2019 (Version 16.11) C++ development, SIMD vectorization and temperature gradient threshold optimization technologies are employed, resulting in a 35% improvement in computational efficiency. Industrial validation results show that, taking 42CrMo steel with a casting speed of 0.24 m/min and a cross-section of φ600 mm as an example, the deviation between the calculated surface temperature (887 °C) and the measured value (876 °C) of the round billet in the straightening zone is only 11 °C, and the calculation error of the cold billet diameter is only 0.325% (with a calculated value of 597.548 mm and a measured average value of 599.5 mm), both meeting the accuracy requirements for engineering applications. The model breaks through the limitations of traditional empirical formulas and provides theoretical support for digital control of continuous casting processes and quality optimization of high-alloy steels. Full article

(This article belongs to the Special Issue Development of Intelligent Forging Process for Metals and Alloys)

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