Metals

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

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)

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14 pages, 16849 KiB

Open AccessArticle

Gradient Dual-Phase Structure Design in Brass: A New Strategy for Balancing Mechanical and Tribological Properties

by Jing Han, Tao Zhang, Bin Zhang, Jing Zhang and Jiyun Zhao

Metals 2025, 15(5), 515; https://doi.org/10.3390/met15050515 - 1 May 2025

Abstract

This study introduces a novel gradient dual-phase structure design in brass, achieved through ultrasonic severe surface rolling (USSR) processing, which enables an unconventional asymmetric bilayer structure—comprising a hardened surface layer (>1 mm thick) and a ductile substrate—distinct from conventional hard-soft-hard sandwich configurations in [...] Read more.

This study introduces a novel gradient dual-phase structure design in brass, achieved through ultrasonic severe surface rolling (USSR) processing, which enables an unconventional asymmetric bilayer structure—comprising a hardened surface layer (>1 mm thick) and a ductile substrate—distinct from conventional hard-soft-hard sandwich configurations in gradient nanostructured materials. Microstructural characterization reveals a gradient dual-phase (α + β’) structure in the hardened layer, progressively transitioning into a homogenized dual-phase structure in the substrate. This unique architecture endows the USSR brass with exceptional mechanical properties, including a yield strength of 582.4 ± 31.0 MPa, ultimate tensile strength of 775.3 ± 33.9 MPa, and retained ductility (9.3 ± 1.0%), demonstrating an outstanding strength-ductility synergy. The USSR brass also demonstrates superior wear resistance with a 42.32% reduction in wear volume and 40.82% decrease in coefficient of friction compared to its as-received counterpart under oil lubrication. This architectural paradigm establishes a robust framework for engineering high-performance brass that simultaneously achieve an exceptional strength-ductility balance and enhanced wear resistance. Full article

16 pages, 3462 KiB

Open AccessArticle

Plasma–Chemical Low-Temperature Reduction of Aluminum with Methane Activated in Microwave Plasma Discharge

by Alexander Logunov, Andrey Vorotyntsev, Igor Prokhorov, Alexey Maslov, Artem Belousov, Ivan Zanozin, Evgeniya Logunova, Sergei Zelentsov, Anton Petukhov and Sergey Suvorov

Metals 2025, 15(5), 514; https://doi.org/10.3390/met15050514 - 1 May 2025

Abstract

High-purity aluminum is widely used in metallurgy, microelectronics and chemical synthesis. In this work, the method of carbothermic reduction of aluminum powder in a microwave plasma discharge with the formation of valuable organic products such as synthesis gas, acetylene and benzene was used. [...] Read more.

High-purity aluminum is widely used in metallurgy, microelectronics and chemical synthesis. In this work, the method of carbothermic reduction of aluminum powder in a microwave plasma discharge with the formation of valuable organic products such as synthesis gas, acetylene and benzene was used. Al powder was studied by inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The yield of by-products was studied by gas chromatography equipped with a mass spectrometer, as well as optical emission spectroscopy of plasma discharge. High-purity aluminum powder reduced with the plasma was used to synthesize oxygen-free trimethylaluminum (TMA). For the first time, TMA was synthesized in one vacuum cycle without the system depressurizing to improve the purity of the final product. Trimethylaluminum was analyzed by gas chromatography, which confirmed that the main substance is ≥99.99% pure. Gas chromatography with a mass spectrometer was used to determine by-products and residual reaction products. Additionally, ICP-MS was used to confirm trace metal concentrations, achieving the 7N standard for ultra-high-purity materials. Full article

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28 pages, 24038 KiB

Open AccessArticle

Advanced Porosity Control of CP780 Galvanized Steel During Gas Metal Arc Welding with Pulsed Arc

by Carlos Adrián García Ochoa, Jorge Alejandro Verduzco Martínez, Francisco Fernando Curiel-López, Víctor Hugo López-Morelos, José Jaime Taha-Tijerina, Ariosto Medina Flores and Maleni García Gómez

Metals 2025, 15(5), 513; https://doi.org/10.3390/met15050513 - 1 May 2025

Abstract

This study investigated the control of porosity during gas metal arc welding with pulsed arc (GMAW-P) of complex-phase 780 (CP780) galvanized steel. Due to the Zn coating on this type of steel, porosity forms during welding as a result of Zn vaporization. The [...] Read more.

This study investigated the control of porosity during gas metal arc welding with pulsed arc (GMAW-P) of complex-phase 780 (CP780) galvanized steel. Due to the Zn coating on this type of steel, porosity forms during welding as a result of Zn vaporization. The objective was to optimize the welding parameters to minimize porosity with a design of experiments using an L9 orthogonal array to analyze the effects of peak current (I_p), pulse time (t_p), and pulse frequency (f) in high-speed welding conditions. The results showed that porosity was significantly reduced with a peak current of 313 A, a frequency of 10 Hz, and a pulse time of 10 ms, achieving ~0% porosity in the validation welding trials. A microstructural analysis identified allotriomorphic ferrite, Widmanstätten ferrite, acicular ferrite, bainite, and martensite in the heat-affected zone (HAZ). A predictive model to anticipate the percentage of porosity with an R² of 99.97% was developed, and an ANOVA determined the peak current as the most critical factor in porosity formation. Full article

(This article belongs to the Special Issue Intelligent and Sustainable Welding: State of the Art, Challenges and Prospects)

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23 pages, 7979 KiB

Open AccessArticle

Constitutive Model for Hot Deformation Behavior of Fe-Mn-Cr-Based Alloys: Physical Model, ANN Model, Model Optimization, Parameter Evaluation and Calibration

by Jie Xu, Chaoyang Sun, Huijun Liang, Lingyun Qian and Chunhui Wang

Metals 2025, 15(5), 512; https://doi.org/10.3390/met15050512 - 1 May 2025

Abstract

The development and validation of constitutive models for high-temperature deformation are critical for bridging microstructure evolution with macroscopic mechanical behavior in materials. In this study, we systematically analyzed the hot deformation behavior of Fe-Mn-Cr-based alloys, compared the modeling processes of physical, phenomenological, and [...] Read more.

The development and validation of constitutive models for high-temperature deformation are critical for bridging microstructure evolution with macroscopic mechanical behavior in materials. In this study, we systematically analyzed the hot deformation behavior of Fe-Mn-Cr-based alloys, compared the modeling processes of physical, phenomenological, and data-driven approaches in detail, and optimized their structural and predictive properties. First, the advantages, disadvantages, and applicability of three traditional models, namely the physical Arrhenius model, the phenomenological Johnson–Cook model, and the artificial neural network (ANN) model, are compared for flow stress prediction. Subsequently, traditional mathematical derivations and numerical optimization methods are evaluated. The parameters and architecture of the ANN model are then systematically optimized using optimization algorithms to enhance training efficiency and prediction accuracy. Finally, sensitivity analysis integrated with Bayesian posterior probability density functions enables the calibration of physical model parameters and uncertainty quantification. The results demonstrate that the ANN with optimized parameters and architecture achieves superior prediction accuracy (R² = 0.9985, AARE = 3.01%) compared to traditional methods. Bayesian inference-based quantification of parameter uncertainty significantly enhances the reliability and interpretability of constitutive model parameters. This study not only reveals the strain–temperature coupling effects in the hot deformation behavior of Fe-Mn-Cr-based alloys but also provides systematic methodological support for constitutive modeling of high-performance alloys and a theoretical foundation for material processing technology design. Full article

(This article belongs to the Special Issue Modeling, Simulation and Experimental Studies in Metal Forming)

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15 pages, 6950 KiB

Open AccessArticle

Mechanical and Microstructural Properties of High-Speed Friction Stir Welding of AA 7020 Aluminum Alloy Using Multi-Pin Tool

by Ramin Delir Nazarlou, Samita Salim, Michael Wiegand, Christian Wolf and Stefan Böhm

Metals 2025, 15(5), 511; https://doi.org/10.3390/met15050511 - 30 Apr 2025

Abstract

High-speed friction stir welding (HSFSW) has emerged as a promising technique for improving the manufacturing efficiency of aluminum alloy structures by enabling faster welding while maintaining the quality of welded joints. This study investigates the mechanical properties and microstructural characteristics of AA 7020-T651 [...] Read more.

High-speed friction stir welding (HSFSW) has emerged as a promising technique for improving the manufacturing efficiency of aluminum alloy structures by enabling faster welding while maintaining the quality of welded joints. This study investigates the mechanical properties and microstructural characteristics of AA 7020-T651 aluminum alloy joints welded using a novel multi-pin tool at high feed rates ranging from 2500 to 6000 mm/min under a constant rotational speed of 4000 rpm. Defect-free welds were successfully fabricated, as confirmed by metallographic analysis and micro-computed tomography (µCT). The multi-pin tool facilitated consistent material flow and heat distribution, which contributed to reliable joint formation across all feed rates. At the highest feed rate, the tensile strength reached 76% of the base material. A consistent softening in the nugget zone (NZ) was observed, and electron backscatter diffraction (EBSD) analysis showed a more than 70% grain size reduction in this zone, averaging ~3 µm, due to dynamic recrystallization. These findings underscore the suitability of HSFSW with multi-pin tools for high-speed industrial applications, offering enhanced productivity without compromising structural integrity. Full article

(This article belongs to the Section Welding and Joining)

23 pages, 3143 KiB

Open AccessArticle

Enhanced Corrosion Resistance of Carbon Steel Rebar in Chloride-Containing Water Solutions: The Role of Lotus Extract in Corrosion Inhibition

by Dan Song, Juhang Wang, Hao Guan, Sijie Zhang, Zhou Zhou and Shuguang Zhang

Metals 2025, 15(5), 510; https://doi.org/10.3390/met15050510 - 30 Apr 2025

Abstract

Corrosion inhibitors play a crucial role in the corrosion protection of rebars in reinforced concrete structures under harsh service conditions. However, conventional corrosion inhibitors often suffer from low efficiency and environmental concerns. This study investigates a low-cost and environmentally friendly lotus leaf extract [...] Read more.

Corrosion inhibitors play a crucial role in the corrosion protection of rebars in reinforced concrete structures under harsh service conditions. However, conventional corrosion inhibitors often suffer from low efficiency and environmental concerns. This study investigates a low-cost and environmentally friendly lotus leaf extract (LLE) as a corrosion inhibitor and examines its effects on carbon steel rebar corrosion under various conditions. The structure and composition of LLE were characterized using SEM, FTIR, and LC-MS. The effects of LLE on rebar corrosion behavior under different environmental conditions were investigated using electrochemical tests, Mott–Schottky analysis, and XPS. The main findings indicate that LLE is rich in polar chemical bonds and functional groups, which facilitate adsorption and film formation on the rebar surface. In a 3.5% NaCl solution, rebar corrosion is primarily influenced by the solution pH, and low concentrations of LLE exhibit effective corrosion inhibition. In a simulated concrete pore solution, higher concentrations of LLE promote the formation of a passivation film in a chloride-alkaline environment. Studies on pre-passivated rebar indicate that LLE effectively protects the passivation film, with the optimal LLE concentration for passivation film protection and adsorption film quality being 0.5 wt%. This study contributes to the application and development of novel LLE-based corrosion inhibition technology for carbon steel rebar. Full article

(This article belongs to the Special Issue Corrosion Behavior of Alloys in Water Environments)

19 pages, 5706 KiB

Open AccessArticle

The Effect of Quenching and Partitioning (Q&P) Processing on the Microstructure, Hardness, and Corrosion Resistance of SAE 9254 Spring Steel

by Alisson Denis Carros Nizes, Silvano Leal dos Santos and Renato Altobelli Antunes

Metals 2025, 15(5), 509; https://doi.org/10.3390/met15050509 - 30 Apr 2025

Abstract

In the present work, the effect of quenching and partitioning cycles on the microstructure, hardness, and corrosion behavior of SAE 9254 spring steel was investigated. Initially, the critical phase transformation temperatures were analyzed by dilatometry. The samples were then treated by four routes [...] Read more.

In the present work, the effect of quenching and partitioning cycles on the microstructure, hardness, and corrosion behavior of SAE 9254 spring steel was investigated. Initially, the critical phase transformation temperatures were analyzed by dilatometry. The samples were then treated by four routes of quenching and partitioning in a dilatometer with quenching stop temperatures of 250 and 220 °C. The partitioning temperatures were 300 and 400 °C. The partitioning time was 480 s. Quantitative characterization of austenite and martensite volume fractions was carried out by X-ray diffraction. Qualitative characterization was carried out by optical microscopy and scanning electron microscopy in addition to quantitative assessments of the chemical composition of segregations by EDS. The formation of martensite, retained austenite, and bainite was observed. The dilatometric curves displayed the occurrence of volumetric expansion in the partitioning step, indicating the formation of secondary martensite (fresh martensite) during the final cooling process (final quenching). The mechanical properties were evaluated by Vickers microhardness and nanoindentation tests. There was heterogeneity of hardness inside and outside the banding regions. The electrochemical properties were evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization tests in a 0.1 M H₂SO₄ solution. The best corrosion resistance was achieved for samples quenched at 250 °C and partitioned at 400 °C due to the higher volume fraction of retained austenite when compared to the other heat treatment conditions. Full article

(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials (Third Edition))

12 pages, 17365 KiB

Open AccessArticle

Study of the Behavior and Mechanism of Sponge Iron Oxidation

by Pingguo Jiang, Chen Zhang, Xionggang Lu and Wangjun Peng

Metals 2025, 15(5), 508; https://doi.org/10.3390/met15050508 - 30 Apr 2025

Abstract

This paper investigates the kinetic characteristics of sponge iron powder reoxidation under two different oxidation atmospheres by examining the reoxidation process from thermodynamic, microstructural, and kinetic perspectives. It reveals the changes in the surface microstructure and oxide content of sponge iron under different [...] Read more.

This paper investigates the kinetic characteristics of sponge iron powder reoxidation under two different oxidation atmospheres by examining the reoxidation process from thermodynamic, microstructural, and kinetic perspectives. It reveals the changes in the surface microstructure and oxide content of sponge iron under different oxidation conditions. The results indicate that the thermodynamic conditions for the formation of Fe₂O₃ were more relaxed than those for Fe₃O₄. As the oxidation time increased, the surface microstructure of the sponge iron transitioned from a porous granular form (Fe) to a dense blocky structure (Fe₃O₄), eventually forming a rod-like product (Fe₂O₃). Under an atmosphere of O₂/Ar = 21/79, the oxide content was significantly higher compared to an atmosphere of O₂/Ar = 11/89. Under an atmosphere of O₂/Ar = 11/89, the oxidation rate index (n) remained at 0.68 throughout all stages, indicating a consistently higher oxidation rate. Conversely, under an atmosphere of O₂/Ar = 21/79, the initial oxidation rate index (n₁) was 1.17, reflecting a slower initial oxidation rate, while in the final stage, the oxidation rate index (n₂) dripped to 0.33, indicating a substantial increase in the oxidation rate. The research results provide basic research ideas and references for an in-depth study of the antioxidant storage of sponge iron. Full article

(This article belongs to the Section Extractive Metallurgy)

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20 pages, 5677 KiB

Open AccessArticle

Influence of Ni60-WC Bionic Unit on the Wear Performance of 20CrMnTi Steel Prepared via Laser Cladding

by Bo Cui, You Lv, Zhaolong Sun and Yan Tong

Metals 2025, 15(5), 507; https://doi.org/10.3390/met15050507 - 30 Apr 2025

Abstract

In recent years, the field of bionic engineering has advanced at a remarkable pace. Numerous engineering challenges have been addressed through inspiration drawn from biological organisms in nature. In this paper, laser cladding was employed to fabricate a bionic unit inspired by the [...] Read more.

In recent years, the field of bionic engineering has advanced at a remarkable pace. Numerous engineering challenges have been addressed through inspiration drawn from biological organisms in nature. In this paper, laser cladding was employed to fabricate a bionic unit inspired by the radial ribs of the bivalve shell surface morphology on 20CrMnTi steel, with the aim of enhancing its wear performance. The metallic powder used in the experiments was prepared by blending Ni60 alloy powder with tungsten carbide (WC) in a predetermined ratio. The WC content was maintained within a mass percentage range of 15% to 60% in the composite powder system. The microstructure and properties of the bionic unit were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and a hardness tester, while its dry sliding wear resistance was evaluated using a block-on-ring tribometer. The influence of the WC content on the microstructure, hardness, surface roughness, and wear performance of the bionic unit was investigated. The experimental results revealed that the bionic unit exhibited a dual microstructure comprising equiaxed crystals and fine dendritic structures. The incorporation of WC induced pronounced grain refinement, while the dispersed WC particles formed effective metallurgical bonding with the Ni-substrate. A positive correlation was observed between the WC content and hardness, with peak hardness reaching 1008 HV_0.2 at 60% WC. Tribological analysis demonstrated a wear mechanism transition from dominant abrasive wear to a hybrid abrasive–adhesive wear. The wear volume of the bionic unit decreased with increasing WC content, and the extent of damage was reduced. Full article

18 pages, 3666 KiB

Open AccessArticle

Failure Analysis and Corrosion Resistance of Carbon Steel Pipelines in Concentrated Sulfuric Acid

by Guofu Ou, Xiaomin Cao, Yusif Mukhtar Mohammed and Wangping Wu

Metals 2025, 15(5), 506; https://doi.org/10.3390/met15050506 - 30 Apr 2025

Abstract

This study examines the waste sulfuric acid pipeline within the waste acid system from a certain petrochemical company, specifically, related to its sulfuric acid alkylation process. The current study sought to investigate the corrosion perforation mechanism of pipelines and revealed the synergistic effects [...] Read more.

This study examines the waste sulfuric acid pipeline within the waste acid system from a certain petrochemical company, specifically, related to its sulfuric acid alkylation process. The current study sought to investigate the corrosion perforation mechanism of pipelines and revealed the synergistic effects of sulfuric acid temperature and concentration on the corrosion behavior of 20# carbon steel. The corrosion features of the failed part were analyzed by scanning electron microscopy, X-ray energy-dispersive spectroscopy, and X-ray diffraction. The corrosion rates of 20# carbon steel in sulfuric acid at different concentrations (80%, 90%, 98%) and working temperatures (20 °C, 40 °C) were measured using the immersion corrosion method, potentiodynamic polarization curves, and electrochemical impedance spectroscopy. The results indicate that the failed pipeline exhibited multi-form corrosion characteristics, with both uniform and localized corrosion occurring simultaneously in concentrated sulfuric acid. The lowest corrosion rate was 0.0795 mm/a in 98% H₂SO₄ at 40 °C. The sulfuric acid concentration and working temperature exhibited synergistic effects on the corrosion behavior of 20# carbon steel. The corrosion rates increased with concentration in the range of 80–90% H₂SO₄ but reached a minimum of 98% due to passive film formation. In a nutshell, we established that elevated temperatures accelerated corrosion in low-concentration systems, but triggered localized active dissolution in high-concentration systems by disrupting the passive film on the surface of the steel. Full article

(This article belongs to the Special Issue Corrosion Behavior of Carbon Steels in Natural and Industrial Environments—2nd Edition)

25 pages, 1831 KiB

Open AccessArticle

Application of Machine Learning in Predicting Quality Parameters in Metal Material Extrusion (MEX/M)

by Karim Asami, Maxim Kuehne, Tim Röver and Claus Emmelmann

Metals 2025, 15(5), 505; https://doi.org/10.3390/met15050505 - 30 Apr 2025

Abstract

Additive manufacturing processes such as the material extrusion of metals (MEX/M) enable the production of complex and functional parts that are not feasible to create through traditional manufacturing methods. However, achieving high‑quality MEX/M parts requires significant experimental and financial investments for suitable parameter [...] Read more.

Additive manufacturing processes such as the material extrusion of metals (MEX/M) enable the production of complex and functional parts that are not feasible to create through traditional manufacturing methods. However, achieving high‑quality MEX/M parts requires significant experimental and financial investments for suitable parameter development. In response, this study explores the application of machine learning (ML) to predict the surface roughness and density in MEX/M components. The various models are trained with experimental data using input parameters such as layer thickness, print velocity, infill, overhang angle, and sinter profile enabling precise predictions of surface roughness and density. The various ML models demonstrate an accuracy of up to 97% after training. In conclusion, this research showcases the potential of ML in enhancing the efficiency in control over component quality during the design phase, addressing challenges in metallic additive manufacturing, and facilitating exact control and optimization of the MEX/M process, especially for complex geometrical structures. Full article

(This article belongs to the Special Issue Machine Learning in Metal Additive Manufacturing)

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19 pages, 2029 KiB

Open AccessArticle

Detection of Q235 Mild Steel Resistance Spot Welding Defects Based on EMD-SVM

by Yuxin Wu, Xiangdong Gao, Dongfang Zhang and Perry Gao

Metals 2025, 15(5), 504; https://doi.org/10.3390/met15050504 - 30 Apr 2025

Abstract

Real-time detection of welding defects in resistance spot welding is a complex challenge. Dynamic resistance (DR) reflects nugget growth and varies with defect types, serving as a key indicator. This study presents an online quality evaluation and defect classification method for Q235 low-carbon [...] Read more.

Real-time detection of welding defects in resistance spot welding is a complex challenge. Dynamic resistance (DR) reflects nugget growth and varies with defect types, serving as a key indicator. This study presents an online quality evaluation and defect classification method for Q235 low-carbon steel welding. Welding current and voltage were collected in real-time, and DR signals were processed employing a second-order Butterworth low-pass filter featuring zero-phase processing to enhance accuracy. Empirical mode decomposition (EMD) decomposed these signals into intrinsic mode functions (IMFs) and residuals, which were classified by a support vector machine (SVM). Experiments showed the EMD-SVM method outperforms traditional approaches, including backpropagation (BP) neural networks, SVM, wavelet packet decomposition (WPD)-BP, WPD-SVM, and EMD-BP, in identifying four welding states: normal, spatter, false, and edge welding. This method provides an efficient, robust solution for online defect detection in resistance spot welding. Full article

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

18 pages, 4370 KiB

Open AccessArticle

Lightweight Ti₃VNbAl_0.5Zr_x (x = 0, 0.1, 0.5, and 1) Refractory High-Entropy Alloys with an Optimized Balance of Strength and Ductility

by Haoyu Fang, Xuejiao Wang, Aidong Lan, Xi Jin and Junwei Qiao

Metals 2025, 15(5), 503; https://doi.org/10.3390/met15050503 - 30 Apr 2025

Abstract

Achieving a balance between strength and room-temperature ductility remains an urgent need and a significant challenge for body-centered cubic (BCC) structure materials. In this paper, a good combination of strength and ductility in single-phase BCC-structured Ti₃VNbAl_0.5Zr_x (x = [...] Read more.

Achieving a balance between strength and room-temperature ductility remains an urgent need and a significant challenge for body-centered cubic (BCC) structure materials. In this paper, a good combination of strength and ductility in single-phase BCC-structured Ti₃VNbAl_0.5Zr_x (x = 0, 0.1, 0.5, and 1) lightweight high-entropy alloys (LHEAs) was designed by reducing the valence-electron concentration in combination with the d-electron theory. The influences of Zr on the microstructures and mechanical properties of the alloys were systematically studied. The yield strengths of Zr0, Zr0.1, Zr0.5, and Zr1 alloys were 644 MPa, 703 MPa, 827 MPa, and 904 Mpa, respectively. The tensile strains of Zr0, Zr0.1, Zr0.5, and Zr1 alloys were 29%, 30%, 20%, and 16%, respectively. The deformation mechanism was studied using transmission electron microscopy (TEM). The results demonstrate that the alloys could still maintain single-phase BCC structure after deformation, and neither phase transformation nor twinning was detected during the deformation process. The main deformation mechanism of the Zr1 alloy is dislocation slip. The current work has great significance for developing high-strength, ductile, and low-density structural materials. Full article

(This article belongs to the Special Issue Feature Papers in Entropic Alloys and Meta-Metals)

15 pages, 3105 KiB

Open AccessArticle

Study of Tensile Fracture and Interfacial Strength of 316L/Q345R Stainless Steel Composite Plate Based on Molecular Dynamics

by Lu Xie, Junhao Kang, Xuefei Fu and Wenrui Wang

Metals 2025, 15(5), 502; https://doi.org/10.3390/met15050502 - 30 Apr 2025

Abstract

This study employs molecular dynamics (MD) simulations to investigate the interface adhesive strength of 316L/Q345R stainless steel composite plates. An atomic model of the 316L/Q345R interface was developed, and tensile performance simulations were conducted to analyze the effects of temperature and strain rate [...] Read more.

This study employs molecular dynamics (MD) simulations to investigate the interface adhesive strength of 316L/Q345R stainless steel composite plates. An atomic model of the 316L/Q345R interface was developed, and tensile performance simulations were conducted to analyze the effects of temperature and strain rate on the material’s mechanical properties. The results demonstrate that the 316L/Q345R interface exhibits superior strength and plasticity compared to both Q345R and 316L individually, with the interface strength being 19.61% higher than Q345R and 29.98% higher than 316L. The study reveals that the ultimate stress of the interface decreases with increasing temperature in the range of 300 K to 600 K, showing a reduction of approximately 0.06 σ₀ for every 100 K increase. Additionally, within the strain rate range of 4 × 10⁷ s⁻¹ to 4 × 10⁸ s⁻¹, both the ultimate stress and fracture strain of the interface decrease as the strain rate increases. These findings provide valuable insights into the interface performance of 316L/Q345R stainless steel composite plates, contributing to the understanding of their mechanical behavior under various conditions. Full article

(This article belongs to the Special Issue Design, Preparation and Properties of High Performance Steels (2nd Edition))

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18 pages, 3769 KiB

Open AccessArticle

Effect of Inter-Pass Temperature and Time on Martensite Formation in the Heat-Affected Zone During Multi-Pass Welding of P91 Steel

by Druce Dunne, Huijun Li and Elena Pereloma

Metals 2025, 15(5), 501; https://doi.org/10.3390/met15050501 - 30 Apr 2025

Abstract

Dilatometry was used to simulate and analyze martensite formation in the grain-coarsened heat-affected zone (GCHAZ) of P91 steel for high inter-pass temperatures during multi-pass welding. The inter-pass temperature of 360 °C was within the dual-phase temperature range (~400 °C to 240 °C), but [...] Read more.

Dilatometry was used to simulate and analyze martensite formation in the grain-coarsened heat-affected zone (GCHAZ) of P91 steel for high inter-pass temperatures during multi-pass welding. The inter-pass temperature of 360 °C was within the dual-phase temperature range (~400 °C to 240 °C), but because of the unexpected formation of isothermal martensite, the microstructure at the inter-pass temperature was substantially martensitic and similar in microstructure and hardness to those obtained using lower, conventional inter-pass temperatures (about 250 °C). The results for martensite formation indicate that kinetic classifications for transformation in carbon and alloyed steels should take into account the overlapping effects of the diffusionless transformation and thermally activated processes associated with dislocation motion and the diffusion of interstitial elements. Furthermore, the M_S temperature was found to be highly sensitive to the microstructural state of the austenite and the availability of nucleating sites for martensite formation. The data for the kinetics of martensite formation were inconsistent with the widely used Koistinen and Marburger (KM) equation for predicting the volume fraction of martensite as a function of quench temperature. It is concluded that the KM equation has limited applicability Full article

(This article belongs to the Special Issue Phase Transformation and Softening Mechanisms of Metals and Alloys during Thermomechanical Processing)

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14 pages, 9208 KiB

Open AccessArticle

Effect of Intermediate Annealing Before Cold Rolling on Microstructure and Mechanical Properties of Medium Manganese Steel and Mechanism of Phase Transformation Plasticity

by Shun Yao, Kuo Cao, Di Wang, Junming Chen and Aimin Zhao

Metals 2025, 15(5), 500; https://doi.org/10.3390/met15050500 - 30 Apr 2025

Abstract

To address the issue of cracking in cold-rolled medium manganese steel caused by the formation of a large amount of martensite after hot rolling, intermediate annealing was conducted prior to cold rolling. The research results indicate that after 1 h of intermediate annealing [...] Read more.

To address the issue of cracking in cold-rolled medium manganese steel caused by the formation of a large amount of martensite after hot rolling, intermediate annealing was conducted prior to cold rolling. The research results indicate that after 1 h of intermediate annealing at a temperature of 700 °C, some martensite is replaced by ferrite and residual austenite, leading to a reduction in rolling stress. The dissolution of cementite leads to an increase in the solubility of the alloying elements in austenite. This increases the volume fraction and carbon content of austenite. Following cold rolling and final heat treatment, the Mn content is higher in both martensite and residual austenite, while it is relatively lower in ferrite. Elevated C and Mn content enhances the stability of the austenite. The elongation of the sample with intermediate annealing increased from 17% to 27%, and the yield strength slightly decreased. During the tensile process, ferrite provides plasticity during the early stage of deformation. As strain increases, martensite begins to deform, making a significant contribution to the material’s strength. The TRIP effect of austenite contributes most of the plasticity, especially the stable thin-film residual austenite. When the residual austenite is exhausted, the incompatibility between ferrite and martensite leads to crack propagation and eventual fracture. Full article

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14 pages, 4905 KiB

Open AccessArticle

Experimental Study of Process Parameter Effects on Internal Defects in Titanium Coaxial Wire-Based Laser Metal Deposition

by Remy Mathenia, Braden McLain, Todd Sparks and Frank Liou

Metals 2025, 15(5), 499; https://doi.org/10.3390/met15050499 - 30 Apr 2025

Abstract

Wire-based laser metal deposition is an additive manufacturing process that can be used in the efficient manufacturing of complex structures. This paper utilizes a three-beam coaxial laser wire system to explore the effect of process parameters on the resultant deposition density. The reduction [...] Read more.

Wire-based laser metal deposition is an additive manufacturing process that can be used in the efficient manufacturing of complex structures. This paper utilizes a three-beam coaxial laser wire system to explore the effect of process parameters on the resultant deposition density. The reduction in or elimination of defects is important to the mechanical properties of the additively manufactured material and the widespread adoption of additive manufacturing processes. In this work, two-bead-wide walls were deposited under varying experimental conditions, including the traverse feed rate and workpiece illumination proportion. A method for calculating the bead pitch and layer height increment based on the geometry of the deposited material was developed. The deposited samples were micro-CT-scanned to characterize internal defects at a high resolution. The volume of the detected defects was measured and compared to the total sample volume to calculate a defect rate for each run of the experiment. The traverse feed rate and defocusing level were found to have a significant impact on the output defect rate. As these process parameters were increased, the defect rate decreased. Across the experimental levels, the defect volume percentage was reduced from 1.021% to 0.062%. This reduction in internal defect size enhances the material’s mechanical performance and ensures its suitability for aerospace applications. Full article

(This article belongs to the Special Issue Additive Manufacturing and Processing of Metallic Alloys and Composites)

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22 pages, 11582 KiB

Open AccessArticle

Research on the Structure and Mechanical Properties of Mesh Powder Composite Copper Microporous Materials

by Liuyang Duan, Zhiwen Zhao and Wuyi Ming

Metals 2025, 15(5), 498; https://doi.org/10.3390/met15050498 - 29 Apr 2025

Abstract

With the proliferation of flexible electronics, the advancement of mechanically compliant thermal management systems, notably flexible heat pipes, is imperative to address evolving demands for adaptive thermal regulation in deformable device architectures. The wicks of heat pipes commonly utilize porous copper. In this [...] Read more.

With the proliferation of flexible electronics, the advancement of mechanically compliant thermal management systems, notably flexible heat pipes, is imperative to address evolving demands for adaptive thermal regulation in deformable device architectures. The wicks of heat pipes commonly utilize porous copper. In this study, three types of porous copper materials were fabricated: sintered pure copper powder, sintered copper powder with a copper mesh (as a reinforcing network), and sintered copper powder with NaCl (as a pore-forming agent). Their pore structure characteristics, tensile, and compressive mechanical properties were systematically investigated. Results demonstrated that incorporating NaCl into copper powder significantly increased porosity and enlarged pore size, thereby enhancing permeability. For instance, compared to sintered pure copper powder, the addition of NaCl increased the average pore diameter from 0.31 μm to 2.44 μm and improved permeability from 1.908 × 10⁻¹⁴ m² to 2.832 × 10⁻¹² m², effectively reducing fluid flow resistance. The introduction of copper mesh notably improved mechanical performance: under a sintering temperature of 900 °C, tensile strength increased from 121.6 MPa to 132.2 MPa, and compressive strength rose from 443.5 MPa to 458.4 MPa. However, NaCl-added porous copper exhibited a drastic decline in tensile strength. Consequently, NaCl-modified porous copper is unsuitable for flexible wick applications, whereas copper mesh-reinforced porous copper shows potential as a flexible wick, though further investigation is required to enhance its permeability mechanisms. Full article

(This article belongs to the Special Issue Microstructural Characteristics and Mechanical Behavior of Particle-Reinforced Copper-Based Composites)

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