Metals

15 pages, 1250 KiB

Open AccessArticle

Fatigue Life Analysis of Cruciform Specimens Under Biaxial Loading Using the Paris Equation

by Ahmed Al-Mukhtar and Carsten Koenke

Metals 2025, 15(6), 579; https://doi.org/10.3390/met15060579 - 23 May 2025

The presence of mixed-mode stresses, combining both opening and shearing components, complicates fatigue life estimation when applying the Paris law. To address this, the crack path, along with Mode-I (opening) and Mode-II (shear) components, was numerically analyzed using Fracture Analysis Code (Franc2D) based [...] Read more.

The presence of mixed-mode stresses, combining both opening and shearing components, complicates fatigue life estimation when applying the Paris law. To address this, the crack path, along with Mode-I (opening) and Mode-II (shear) components, was numerically analyzed using Fracture Analysis Code (Franc2D) based on the linear elastic fracture mechanics (LEFM) approach. Accordingly, fatigue life and stress intensity factors (SIFs) under various biaxial loading ratios (λ) were calculated using the Paris law and compared with available data in the literature. The results show that crack growth is primarily driven by the Mode-I component, which exhibits the largest magnitude. Thus, the Mode-I stress intensity factor (K_I) was adopted for the numerical integration of the fatigue life equation. Furthermore, the influence of normal and transverse loads (σ_y and σ_x, respectively) on the crack path plane and SIF was examined for λ. The analysis revealed that lower λ values led to faster crack propagation, while higher λ values resulted in extended fatigue life due to an increased number of cycles to failure. The comparison demonstrated good agreement with reference data, confirming the reliability of the proposed modeling approach over a wide range of biaxial loading conditions. Full article

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

20 pages, 29323 KiB

Open AccessArticle

CALPHAD-Assisted Analysis of Fe-Rich Intermetallics and Their Effect on the Mechanical Properties of Al-Fe-Si Sheets via Continuous Casting and Direct Rolling

by Longfei Li, Xiaolong Li, Lei Shi, Shouzhi Huang, Cong Xu, Guangxi Lu and Shaokang Guan

Metals 2025, 15(6), 578; https://doi.org/10.3390/met15060578 - 23 May 2025

Abstract

As an eco-efficient short-process manufacturing technique for aluminum alloys, twin-belt continuous casting and direct rolling (TBCCR) demonstrates significant production advantages. In this study, an Al-Fe-Si alloy system with different Fe-rich intermetallics (α-AlFe(Mn)Si and β-AlFe(Mn)Si) via TBCCR was developed for new energy vehicle batteries, [...] Read more.

As an eco-efficient short-process manufacturing technique for aluminum alloys, twin-belt continuous casting and direct rolling (TBCCR) demonstrates significant production advantages. In this study, an Al-Fe-Si alloy system with different Fe-rich intermetallics (α-AlFe(Mn)Si and β-AlFe(Mn)Si) via TBCCR was developed for new energy vehicle batteries, utilizing the Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD) technique. Comprehensive microstructure and surface segregation analyses of continuous casted ingots and direct-rolled sheets revealed that the Al-Fe-Si alloy with a combined Fe + Si content of 0.7% and an optimal Fe/Si atomic ratio of 3:1 (FS31) presents optimized mechanical properties: ultimate tensile strength of 145.8 MPa, elongation to failure of 5.7%, accompanied by a cupping value of 6.64 mm. Notably, Mn addition further refined the grain structure of casting ingots and enhanced the strength of both ingots and rolled sheets. Among the experimental alloys, FS14 (optimal Fe/Si atomic ratio of 1:4) sheets displayed the least surface segregation upon Mn incorporation. Through systematic optimization, an Al-Fe-Si-Mn alloy composition (Fe + Si = 0.7%, Fe/Si = 1:4 atomic ratio, 0.8 wt.% Mn) was engineered for TBCCR processing, achieving enhanced comprehensive performance: ultimate tensile strength of 189.4 MPa, elongation to failure of 7.32%, and cupping value of 7.71 mm. This composition achieves an optimal balance between grain refinement, mechanical properties (strength–plasticity synergy), formability (cupping value), and corrosion resistance (corrosion current density). The performance optimization strategy integrates synergistic improvements in strength, ductility, and corrosion resistance, providing valuable guidance for developing high-performance aluminum alloys suitable for the TBCCR process. Full article

(This article belongs to the Special Issue Thermodynamics and Kinetics Analysis of Metallic Material)

► Show Figures

Figure 1

17 pages, 3064 KiB

Open AccessArticle

Effect of Elastic Strain Energy on Dynamic Recrystallization During Friction Stir Welding of Dissimilar Al/Mg Alloys

by Faliang He, Lei Shi and Chuansong Wu

Metals 2025, 15(6), 577; https://doi.org/10.3390/met15060577 - 23 May 2025

Abstract

Dynamic recrystallization (DRX) is a critical microstructural evolution mechanism in friction stir welding (FSW) of metallic materials, directly determining the mechanical properties and corrosion resistance of weld joints. In the field of DRX simulation, conventional models primarily consider intragranular dislocation strain energy as [...] Read more.

Dynamic recrystallization (DRX) is a critical microstructural evolution mechanism in friction stir welding (FSW) of metallic materials, directly determining the mechanical properties and corrosion resistance of weld joints. In the field of DRX simulation, conventional models primarily consider intragranular dislocation strain energy as the driving force for recrystallization, while neglecting the elastic strain energy generated by coordinated deformation in polycrystalline materials. This study presents an improved DRX modeling framework that incorporates the multiphase-field method to systematically investigate the role of elastic strain energy in microstructural evolution during FSW of Al/Mg dissimilar materials. The results demonstrate that elastic strain energy can modulate nucleation and the growth of recrystallized grains during microstructural evolution, resulting in post-weld average grain size increases of 0.8% on the Al side and 2.1% on the Mg side in the FSW nugget zone. This research provides new insights into multi-energy coupling mechanisms in DRX simulation and offers theoretical guidance for process optimization in dissimilar material welding. Full article

(This article belongs to the Special Issue Friction Stir Welding and Processing of Dissimilar Materials)

19 pages, 5248 KiB

Open AccessArticle

Study on the Austenite Grain Growth Behavior of Fe-Mn-Al-C Low-Density Steel Containing Niobium

by Litu Huo, Tao Ma, Weimin Gao, Yungang Li, Haichao Zhang and Jianxin Gao

Metals 2025, 15(6), 576; https://doi.org/10.3390/met15060576 - 23 May 2025

Abstract

To explore the impact of niobium (Nb) addition on the austenitization behavior of Fe-Mn-Al-C lightweight steels, the effects were examined through Thermo-Calc thermodynamic simulations, optical microscopy, transmission electron microscopy (TEM), and the development of austenite grain growth models. Three distinct Fe-Mn-Al-C steel compositions, [...] Read more.

To explore the impact of niobium (Nb) addition on the austenitization behavior of Fe-Mn-Al-C lightweight steels, the effects were examined through Thermo-Calc thermodynamic simulations, optical microscopy, transmission electron microscopy (TEM), and the development of austenite grain growth models. Three distinct Fe-Mn-Al-C steel compositions, each containing different Nb contents (0.38%, and 0.56%), were subjected to various austenitization temperatures and aging conditions, and a kinetic model for austenite grain growth was established. The results demonstrate that for heating temperatures below 950 °C, the austenite grain growth rate of the steels was similar. However, at temperatures above 950 °C, the grain growth rate of the steel without Nb (Steel No. 1) increased significantly compared to the niobium-containing alloys. Austenite grain size increased with higher heating temperatures. At constant heating temperatures, longer holding times resulted in larger grain sizes, though the rate of grain size growth diminished over time. Based on the experimental data and the kinetic theory of austenite grain growth, a grain growth model of No. 2 Steel (which contained 0.38% Nb) was established. The predicted grain size values derived from this model closely matched the experimental measurements, indicating a strong correlation and providing valuable insights for future studies. Full article

23 pages, 3386 KiB

Open AccessArticle

Influence of Submerged Entry Nozzle Offset on the Flow Field in a Continuous Casting Mold

by Pengcheng Xiao, Ruifeng Wang, Liguang Zhu and Chao Chen

Metals 2025, 15(6), 575; https://doi.org/10.3390/met15060575 - 23 May 2025

Abstract

During the continuous casting process, the submerged entry nozzle (SEN) should be maintained at the geometric center of the mold. However, in actual production, factors such as deformation of the tundish bottom and inaccurate positioning of the traversing car occasionally cause SEN offset. [...] Read more.

During the continuous casting process, the submerged entry nozzle (SEN) should be maintained at the geometric center of the mold. However, in actual production, factors such as deformation of the tundish bottom and inaccurate positioning of the traversing car occasionally cause SEN offset. SEN offset can make the molten steel flow field in the mold asymmetric, increasing the risks of slag entrainment on the surface of the casting blank and breakout accidents. To evaluate the influence of different SEN offsets on the mold flow field, this study uses a slab continuous casting mold with a cross-section of 920 mm × 200 mm from a specific factory as the research object. Mathematical simulations were used to investigate the influence of SEN offsets (including width-direction and thickness-direction offsets) on the flow behavior of molten steel in the mold. A physical water model at a 1:1 scale was established for verification. Two parameters, the symmetry index (S) and the bias flow index (N), were introduced to quantitatively evaluate the symmetry of the flow field, and the rationality of the liquid-level fluctuation under this flow field was verified using the F-number (proposed by Japanese experts for mold level fluctuation control) from the index model. The results show the following: when the SEN offset in the thickness direction increases from 0 to 50 mm, the longitudinal symmetry index (Sy) of the molten steel flow field in the mold decreases from 0.969 to 0.704—a reduction of 27.4%; the longitudinal bias flow index (Ny) of molten steel level fluctuation increases from 0.007 to 0.186, representing a 25.6-fold increase, and the F-number rises from 4.297 to 8.482; when the SEN offset in the width direction increases from 0 to 20 mm, the transverse-axis symmetry index (Sx) of the flow field decreases gradually from 0.969 to 0.753 at a 20 mm offset, which is a reduction of approximately 22.29%; the transverse-axis bias flow index (Nx) increases from 0.015 to 0.174 at a 20 mm offset—an increase of 10.6 times; and the F-number increases from 4.297 to 5.548. Considering the comprehensive evaluation of horizontal/vertical symmetry indices, bias flow indices, and F-numbers under the two working conditions, the width-direction SEN offset has the most significant impact on the symmetry of the molten steel flow field. Full article

(This article belongs to the Special Issue Advanced Tundish Metallurgy and Clean Steel Technology—Second Edition)

► Show Figures

Figure 1

24 pages, 6410 KiB

Open AccessArticle

Optimal Diamond Burnishing of Chromium–Nickel Austenitic Stainless Steels Based on the Finishing Process–Surface Integrity–Operating Behavior Correlations

by Jordan Maximov, Galya Duncheva, Mariana Ichkova and Kalin Anastasov

Metals 2025, 15(6), 574; https://doi.org/10.3390/met15060574 - 22 May 2025

Abstract

Chromium–nickel austenitic stainless steels are widely used in various industries after their initial hardness and strength are increased. Apart from low-temperature thermal–chemical diffusion, the mechanical properties can be improved by surface cold working (SCW). A cheap and reliable form of static SCW is [...] Read more.

Chromium–nickel austenitic stainless steels are widely used in various industries after their initial hardness and strength are increased. Apart from low-temperature thermal–chemical diffusion, the mechanical properties can be improved by surface cold working (SCW). A cheap and reliable form of static SCW is diamond burnishing (DB), which drastically improves the surface integrity (SI) and hence the operational behavior of the processed component. To be maximally effective, the DB parameters must be optimized according to a relevant criterion, depending on the desired effect. For high fatigue strength and/or high wear resistance, complex experimental tests are necessary, which require significant time and financial resources. This study presents a cost-effective optimization approach based on the DB process–SI–operating behavior correlations. Using these correlations, in addition to the correlations between appropriately selected SI characteristics, the proposed approach relies on the control of only three easy-to-measure roughness parameters, namely the arithmetic average roughness, skewness, and kurtosis, which, in turn, depend on the governing factors of the DB process. Full article

(This article belongs to the Special Issue Machining Technology for Metallic Materials)

► Show Figures

Figure 1

26 pages, 7824 KiB

Open AccessArticle

Microstructural Synergy of ZrC-NbC Reinforcements and Its Coupled Effects on Mechanical and Dynamic Properties of Titanium Matrix Composites

by Juan Wang, Haijun Zhang, Baiqing Zhou and Zhong Yang

Metals 2025, 15(6), 573; https://doi.org/10.3390/met15060573 - 22 May 2025

Abstract

In aerospace applications, titanium matrix composites (TMCs) must balance high strength, thermal stability, and vibration resistance. This study investigates the microstructural evolution and multi-property correlations in single-phase ZrC-reinforced (TMC1) and dual-phase ZrC-NbC-co-reinforced (TMC2) TMCs via SEM/TEM, XRD, tensile testing, and ANSYS simulations. The [...] Read more.

In aerospace applications, titanium matrix composites (TMCs) must balance high strength, thermal stability, and vibration resistance. This study investigates the microstructural evolution and multi-property correlations in single-phase ZrC-reinforced (TMC1) and dual-phase ZrC-NbC-co-reinforced (TMC2) TMCs via SEM/TEM, XRD, tensile testing, and ANSYS simulations. The in situ reaction (Ti + ZrC/NbC → TiC + Zr/Nb) and NbC-induced grain boundary pinning drive microstructural optimization in TMC2, achieving 30% higher reinforcement homogeneity and 5 μm grain refinement from 15 μm to 10 μm. TMC2’s tensile strength reaches 1210 MPa, a 15% increase over TMC1, with an elongation at a break of 4.74%, 2.2 times that of TMC1. This performance stems from synergistic Hall–Petch strengthening and nano-TiC dispersion strengthening. Modal simulations show TMC2 exhibits a first-mode natural frequency of 98.5 kHz, 1.1% higher than TMC1’s 97.4 kHz, with maximum displacement reduced by 2.3%. These improvements correlate with TMC2’s elevated elastic modulus (125 GPa vs. 110 GPa) and uniform mass/stiffness distribution. The ZrC-NbC synergy establishes a microstructural framework for the concurrent enhancement of static and dynamic properties, offering critical insights for a high-performance TMC design in extreme environments. Full article

► Show Figures

Figure 1

24 pages, 4281 KiB

Open AccessArticle

Copper–Ammonia–Thiosulfate Leaching of High-Sulfide Concentrates: Process Optimization and Additive Effects on Gold Extraction

by Azizbek Bolikulovich Buronov, Blackie Korul Yayabu, Labone Lorraine Godirilwe, Batnasan Altansukh, Sanghee Jeon, Kazutoshi Haga and Atsushi Shibayama

Metals 2025, 15(6), 572; https://doi.org/10.3390/met15060572 - 22 May 2025

Abstract

This research focuses on finding an environmentally friendly method for extracting gold from a sulfide flotation concentrate. In this study, an ammonia–copper–thiosulfate leaching system was utilized for the extraction of gold. The flotation concentrate sample contains about 190 ppm of gold, 160 ppm [...] Read more.

This research focuses on finding an environmentally friendly method for extracting gold from a sulfide flotation concentrate. In this study, an ammonia–copper–thiosulfate leaching system was utilized for the extraction of gold. The flotation concentrate sample contains about 190 ppm of gold, 160 ppm of silver, and 6.89% of copper. To achieve an optimized gold extraction, various parameters, such as thiosulfate, ammonia and copper concentrations, pulp density, pH, stirring rate, temperature, and time, were investigated. About 87% of gold was leached under the following conditions: 0.5 M S₂O₃²⁻, 1.0 M NH₃, 0.1 M Cu²⁺, a stirring rate of 350 rpm, a pH of 12, a pulp density of 10% solids, a temperature of 25 °C, and a leaching time of 2 h. Additionally, to improve the economic effectiveness of the leaching system, thiosulfate consumption was investigated by utilizing different additives, such as diethylenetriamine (DETA), glycerol, and ammonium dihydrogen phosphate (ADP). The results showed that with the use of ADP, gold extraction increased from 87% to 91% while reducing copper dissolution. Additionally, the thiosulfate consumption also decreased from 0.37 M to 0.3 M. The inclusion of ADP was particularly effective, enhancing gold extraction efficiency and reducing reagent consumption, thereby making the process more sustainable. Considering the high economic value of gold, the optimization of recovery efficiency is prioritized over reagent costs in this study. Overall, this study indicates that the optimized ammonia–copper–thiosulfate leaching system with ADP additive is a promising environmentally friendly method for the extraction of gold. Full article

(This article belongs to the Section Extractive Metallurgy)

► Show Figures

Figure 1

12 pages, 14008 KiB

Open AccessArticle

Peculiarities of the Creep Behavior of 15Kh2NMFAA Vessel Steel at High Temperatures

by Egor Terentyev, Artem Marchenkov, Vladimir Loktionov, Anastasia Pankina, Georgy Sviridov, Ksenia Borodavkina, Danila Chuprin and Nikita Lavrik

Metals 2025, 15(6), 571; https://doi.org/10.3390/met15060571 - 22 May 2025

Abstract

The creep properties of 15Kh2NMFAA nuclear WWER (water–water energetic reactor) vessel steel in the range of 500–1200

^{\circ}

C temperatures, which may appear during severe nuclear reactor accidents, were investigated. The present paper attempts to analyze the creep curves obtained from tensile testing [...] Read more.

The creep properties of 15Kh2NMFAA nuclear WWER (water–water energetic reactor) vessel steel in the range of 500–1200

^{\circ}

C temperatures, which may appear during severe nuclear reactor accidents, were investigated. The present paper attempts to analyze the creep curves obtained from tensile testing at high temperatures using the Larson–Miller parametric technique. The power law rate and material coefficient of Norton’s equation with the Monkman–Grant relationship coefficient were found for each test temperature. It is shown that in accordance with the Monkman–Grant relationship coefficient values, changing the creep type from dislocation glide to high temperature dislocation climb occurs in the temperature range of 600–700

^{\circ}

C, which leads to a slope change in the Larson–Miller parameter plot and the conversion of steel creep behavior. It is also shown that in the range of

A_{1}

–

A_{3}

temperatures, a stepwise change in creep characteristics occurs, which is associated with phase transformations. In addition, the constancy of the product of the time to rupture

τ_{r}

and the minimum creep rate

{\dot{ϵ}}_{m i n}

in the ranges of 600–700

^{\circ}

C and

A_{3}

-1200

^{\circ}

C was noted. The proposed approach improves the accuracy of time to rupture estimation of 15Kh2NMFAA steel by at least one order of magnitude. Based on the research results, the calculated dependence of the steel’s long-term strength limit on temperature was obtained for several time bases, allowing us to increase the accuracy of material survivability prediction in the case of a severe accident at a nuclear reactor. Full article

(This article belongs to the Special Issue Advances in Creep Behavior of Metallic Materials)

21 pages, 3118 KiB

Open AccessArticle

Path Planning for Rapid DEDAM Processing Subject to Interpass Temperature Constraints

by Glenn W. Hatala, Edward W. Reutzel and Qian Wang

Metals 2025, 15(6), 570; https://doi.org/10.3390/met15060570 - 22 May 2025

Abstract

Directed energy deposition (DED) additive manufacturing (AM) enables the production of components at a high deposition rate. For certain alloys, interpass temperature requirements are imposed to control heat accumulation and microstructure transformation, as well as to minimize distortion under varying thermal conditions. A [...] Read more.

Directed energy deposition (DED) additive manufacturing (AM) enables the production of components at a high deposition rate. For certain alloys, interpass temperature requirements are imposed to control heat accumulation and microstructure transformation, as well as to minimize distortion under varying thermal conditions. A typical strategy to comply with interpass temperature constraints is to increase the interpass dwell time, which can lead to an increase in the total deposition time. This study aims to develop an optimized tool path that ensures interpass temperature compliance and reduces overall deposition time relative to the conventional sequential deposition path during the DED process. To evaluate this, a compact analytic thermal model is used to predict the thermal history during laser-based directed energy deposition (DED-LB/M) hot wire (lateral feeding) of ER100S-G, a welding wire equivalent to high yield steel. A greedy algorithm, integrated with the thermal model, identifies a tool path order that ensures compliance with the interpass requirement of the material while minimizing interpass dwell time and, thus, the total deposition time. The proposed path planning algorithm is validated experimentally with in situ temperature measurements comparing parts fabricated with the baseline (sequential) deposition path to the modified path (resulting from the greedy algorithm). The experimental results of this study demonstrate that the proposed path planning algorithm can reduce the deposition time by 9.2% for parts of dimensions 66 mm × 73 mm × 16.5 mm, comprising 15 layers and a total of 300 beads. Predictions based on the proposed path planning algorithm indicate that additional reductions in deposition time can be achieved for larger parts. Specifically, increasing the (experimentally validated) part dimension perpendicular to the deposition direction by five-times is expected to result in a 40% reduction in deposition time. Full article

(This article belongs to the Special Issue Laser Processing Technology for Metals)

► Show Figures

Graphical abstract

26 pages, 5303 KiB

Open AccessArticle

Machine Learning-Based Prediction of Fatigue Fracture Locations in 7075-T651 Aluminum Alloy Friction Stir Welded Joints

by Guangming Mi, Guoqin Sun, Shuai Yang, Xiaodong Liu, Shujun Chen and Wei Kang

Metals 2025, 15(5), 569; https://doi.org/10.3390/met15050569 - 21 May 2025

Abstract

Friction stir welding (FSW) is a solid-state joining technique widely used for aluminum alloys in aerospace, automotive, and shipbuilding applications, yet the prediction of fatigue fracture locations within FSW joints remains challenging for structural-life assessment. In this study, we investigate fatigue fracture location [...] Read more.

Friction stir welding (FSW) is a solid-state joining technique widely used for aluminum alloys in aerospace, automotive, and shipbuilding applications, yet the prediction of fatigue fracture locations within FSW joints remains challenging for structural-life assessment. In this study, we investigate fatigue fracture location prediction in 7075-T651 aluminum alloy FSW joints by applying four machine learning methods—decision tree, logistic regression, a three-layer back-propagation artificial neural network (BP ANN), and a novel Quadratic Classification Neural Network (QCNN)—using maximum stress, stress amplitude, and stress ratio as input features. Evaluated on an experimental test set of eight loading conditions, the QCNN achieved the highest accuracy of 87.5%, outperforming BP ANN (75%), logistic regression (50%), and decision tree (37.5%). Building on QCNN outputs and incorporating relevant material property parameters, we derive a Regional Fracture Prediction Formula (RFPF) based on a Fourier-series quadratic expansion, enabling the rapid estimation of fracture zones under varying loads. These results demonstrate the QCNN’s superior predictive capability and the practical utility of the RFPF framework for the fatigue failure analysis and service-life assessment of FSW structures. Full article

(This article belongs to the Special Issue Fatigue Assessment of Metals)

► Show Figures

Figure 1

14 pages, 1940 KiB

Open AccessArticle

Nanoporous CuAuPtPd Quasi-High-Entropy Alloy Prism Arrays for Sustainable Electrochemical Nitrogen Reduction

by Shuping Hou, Ziying Meng, Weimin Zhao and Zhifeng Wang

Metals 2025, 15(5), 568; https://doi.org/10.3390/met15050568 - 21 May 2025

Abstract

Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, [...] Read more.

Electrochemical nitrogen reduction reaction (NRR) has emerged as a promising approach for sustainable ammonia synthesis under ambient conditions, offering a low-energy alternative to the traditional Haber–Bosch process. However, the development of efficient and sustainable electrocatalysts for NRR remains a significant challenge. Noble metals, known for their exceptional chemical stability under electrocatalytic conditions, have garnered considerable attention in this field. In this study, we report the successful synthesis of nanoporous CuAuPtPd quasi-high-entropy alloy (quasi-HEA) prism arrays through “melt quenching” and “dealloying” techniques. The as-obtained alloy demonstrates remarkable performance as an NRR electrocatalyst, achieving an impressive ammonia synthesis rate of 17.5 μg h⁻¹ mg⁻¹ at a potential of −0.2 V vs. RHE, surpassing many previously reported NRR catalysts. This work not only highlights the potential of quasi-HEAs as advanced NRR electrocatalysts but also provides valuable insights into the design of nanoporous multicomponent materials for sustainable energy and catalytic applications. Full article

(This article belongs to the Special Issue Advances in High-Entropy Alloys’ Microstructure, Properties and Preparation)

► Show Figures

Figure 1

19 pages, 3343 KiB

Open AccessArticle

Crystal Plasticity Finite Element Simulation of Tensile Fracture of 316L Stainless Steel Produced by Selective Laser Melting

by Guowei Zeng, Ziyang Huang, Bei Deng and Rui Ge

Metals 2025, 15(5), 567; https://doi.org/10.3390/met15050567 - 21 May 2025

Abstract

Selective Laser Melting (SLM) of 316L stainless steel exhibits great potential prospects for engineering applications due to its high strength, high forming freedom, and low material waste. However, due to the unique processing technology of additive manufacturing, challenges related to the microstructure and [...] Read more.

Selective Laser Melting (SLM) of 316L stainless steel exhibits great potential prospects for engineering applications due to its high strength, high forming freedom, and low material waste. However, due to the unique processing technology of additive manufacturing, challenges related to the microstructure and differences in the mechanical properties of the formed parts are inevitable. To investigate the influence of building direction and grain boundary strength on the fracture parameters of SLM 316L stainless steel, electron backscatter diffraction (EBSD) experiments were conducted to characterize the microstructure of SLM 316L stainless-steel specimens. A representative volume element (RVE) model reflecting the microstructure of SLM 316L stainless steel was established based on a combination of the crystal plastic finite element method (CPFEM) and UMAT subroutine technology. The crystal plasticity parameters were determined by comparing the results of tensile tests. Cohesive elements were employed and inserted at the grain boundaries of the polycrystalline RVE to simulate the intergranular fracture behavior of SLM 316L stainless steel under uniaxial tensile loading. The damage and fracture mechanisms of the material at the microscale were analyzed. The simulated tensile stress–strain curves were in good agreement with the experimental results; hence, the combined CPFEM model is suitable for characterizing the mechanical response and fracture behavior of the SLM 316L stainless steel. The results revealed that cracks initiate at stress concentration sites and propagate along grain boundaries with increasing external load, ultimately leading to rupture. Additionally, the building direction influences the location of microcracks and their propagation significantly. Full article

(This article belongs to the Special Issue Multi-scale Simulation of Metallic Materials (2nd Edition))

► Show Figures

Figure 1

21 pages, 14426 KiB

Open AccessArticle

Corrosion Resistance and Surface Conductivity of 446 Stainless Steel with Electrochemical Cr-Enrichment and Nitridation for Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates

by Ronghai Xu, Yangyue Zhu, Ruigang Zhu and Moucheng Li

Metals 2025, 15(5), 566; https://doi.org/10.3390/met15050566 - 21 May 2025

Abstract

The development of bipolar plate materials with enhanced corrosion resistance and surface conductivity is critical for the commercial application of proton exchange membrane fuel cells (PEMFCs). The corrosion behavior and surface conductivity of electrochemically nitrided 446 stainless steel with and without the pretreatment [...] Read more.

The development of bipolar plate materials with enhanced corrosion resistance and surface conductivity is critical for the commercial application of proton exchange membrane fuel cells (PEMFCs). The corrosion behavior and surface conductivity of electrochemically nitrided 446 stainless steel with and without the pretreatment of Cr-enrichment were investigated in the simulated PEMFC anode and cathode environments (i.e., 0.5 mol L⁻¹ H₂SO₄ + 2 ppm HF solution bubbled with hydrogen or air at 80 °C) using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma–mass spectrometry (ICP-MS), and electrochemical measurement techniques. Extending the nitriding time from 5 to 30 min enhances the surface conductivity but reduces the corrosion resistance. After the pretreatment and 30 min of nitridation, a thin film formed on the specimen surface, which mainly consists of Cr-nitrides and -oxides with atomic fractions of 0.42 and 0.37, respectively. The Cr-enriched and nitrided specimen shows spontaneous passivation in both the simulated cathode and anode environments and higher corrosion potentials, lower passive current densities, and larger polarization resistances in comparison with the directly nitrided specimens. Its stable current densities are about 0.26 and −0.39 μA cm⁻² after 5 h of polarization tests at 0.6 V_SCE in the cathode environment and at −0.1 V_SCE in the anode environment, respectively. Its contact resistance is about 5.0 mΩ cm² under 1.4 MPa, which is close to that of the specimen directly nitrided for 120 min and slightly decreases after the potentiostatic polarization tests. These results indicate that Cr-rich pretreatment improves not only the corrosion resistance and surface conductivity of nitrided specimens but also the efficiency of electrochemical nitridation. Full article

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

► Show Figures

Figure 1

13 pages, 1122 KiB

Open AccessArticle

Physical Property Prediction of High-Temperature Nickel and Iron–Nickel Superalloys Using Direct and Inverse Composition Machine Learning Models

by Jaka Fajar Fatriansyah, Dzaky Iman Ajiputro, Agrin Febrian Pradana, Rio Sudwitama Persadanta Kaban, Andreas Federico, Muhammad Anis, Dedi Priadi and Nicolas Gascoin

Metals 2025, 15(5), 565; https://doi.org/10.3390/met15050565 - 21 May 2025

Abstract

Superalloys are a class of materials renowned for their exceptional ability to retain mechanical properties at elevated temperatures. Nickel superalloys, with a nickel content ranging from 38% to 76%, and iron–nickel superalloys (15–60% iron, 25–45% nickel) are extensively employed within the aviation industry [...] Read more.

Superalloys are a class of materials renowned for their exceptional ability to retain mechanical properties at elevated temperatures. Nickel superalloys, with a nickel content ranging from 38% to 76%, and iron–nickel superalloys (15–60% iron, 25–45% nickel) are extensively employed within the aviation industry due to their resilience in harsh operating environments. These components encounter extreme temperatures during operation, significantly impacting their tensile strength and melting point. Furthermore, high-speed rotation and abrasive conditions necessitate materials with superior hardness. Consequently, material modifications are crucial to ensure that gas turbine components meet their required properties. Machine learning (ML) and deep learning (DL) offer promising solutions for the design of materials with tailored tensile strength, hardness, and melting point properties. This study investigates the efficacy of direct and inverse machine learning models in predicting crucial material properties and composition, respectively. The model with the most favorable prediction accuracy is identified through the systematic variation of key parameters. The findings show that a fully connected feed-forward Artificial Neural Network (ANN) with three hidden layers using ReLU activation functions performs better than the other models. This capability is leveraged to modify the composition of INCONEL-718, successfully achieving significant enhancements in tensile strength (1592 MPa), hardness (152 HRB), and melting point (1665 °C). Full article

(This article belongs to the Section Structural Integrity of Metals)

► Show Figures

Figure 1

22 pages, 4310 KiB

Open AccessReview

The Microstructures and Properties of Cu-Ni-Co-Si Alloys: A Critical Review

by Fang Li, Wenteng Liu, Chao Ding, Shujuan Wang and Xiangpeng Meng

Metals 2025, 15(5), 564; https://doi.org/10.3390/met15050564 - 20 May 2025

Abstract

This review provides an overview of recent advancements in Cu-Ni-Co-Si alloys, focusing on their processing methods, microstructures, and properties. Due to their non-toxic composition, enhanced mechanical properties, and excellent electrical conductivity, Cu-Ni-Co-Si alloys have emerged as a promising alternative to traditional Cu-Be alloys [...] Read more.

This review provides an overview of recent advancements in Cu-Ni-Co-Si alloys, focusing on their processing methods, microstructures, and properties. Due to their non-toxic composition, enhanced mechanical properties, and excellent electrical conductivity, Cu-Ni-Co-Si alloys have emerged as a promising alternative to traditional Cu-Be alloys in the electrical and electronics industry. This review discusses various synthesis techniques, including casting, vacuum induction melting, and additive manufacturing, and evaluates their effects on the formed microstructures. In addition, it explores the influence of different elements and thermal treatments on the alloys’ microstructures and properties, discussing strategies to enhance the properties of Cu-Ni-Co-Si alloys. Key strengthening mechanisms—including precipitation hardening, grain boundary strengthening, and solid solution hardening—are examined in detail, with particular emphasis on their synergistic effects in optimizing alloy performance. Furthermore, future research directions are highlighted, focusing on the optimization of alloying element concentrations and heat treatment protocols to achieve an enhanced balance between strength and electrical conductivity. These improvements are critical for meeting the demanding requirements of advanced applications in electronics and high-reliability components. Full article

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

► Show Figures

Figure 1

27 pages, 20326 KiB

Open AccessArticle

Experimental and Numerical Investigation on Dynamic Shear Behavior of 30CrMnSiNi2A Steel Using Flat-Hat Specimens

by Xinke Xiao, Yuge Wang, Shuaitao Wu and Chuwei Zhou

Metals 2025, 15(5), 563; https://doi.org/10.3390/met15050563 - 20 May 2025

Abstract

An absolutely conflicting value for the incorporation of the Lode parameter into a fracture criterion was reported in the literature when predicting the ballistic resistance of metallic plates failing through shear plugging. In this study, a combined experimental–numerical investigation was conducted to understand [...] Read more.

An absolutely conflicting value for the incorporation of the Lode parameter into a fracture criterion was reported in the literature when predicting the ballistic resistance of metallic plates failing through shear plugging. In this study, a combined experimental–numerical investigation was conducted to understand the dynamic shear fracture behavior under compression–shear stress states. Flat-hat-shaped specimens of 30CrMnSiNi2A high-strength steel were loaded using a Split Hopkinson Pressure Bar apparatus, combining the ultra-high-speed photography technique, digital image correlation method, and microstructure observation. Parallel finite element simulations were performed using both a modified Johnson–Cook (MJC) fracture criterion or an extended Xue–Wierzbicki (EXW) fracture criterion with Lode dependence to reveal the value of the Lode parameter incorporation. It was found that deformed shear bands with a width of approximately 0.14 mm form at a critical impact velocity. The EXW criterion correctly predicts the critical fracture velocity and estimates the fracture initiation instants within an error of 5.3%, whereas the MJC fracture criterion overestimates the velocity by 14.3%. Detailed analysis shows that the EXW criterion predicts a combined failure mechanism involving ductile fracture and material instability, while the MJC fracture criterion attributes the failure exclusively to material instability. The improved accuracy achieved by employing the Lode-dependent EXW fracture criterion may be attributed to the compression–shear stress state and the accurate prediction of the failure mechanism of the dynamic shear fracture. Full article

(This article belongs to the Special Issue Deformation of Metals and Alloys: Theory, Simulations and Experiments—2nd Edition)

► Show Figures

Figure 1

15 pages, 2698 KiB

Open AccessArticle

Geometric Analysis of the Scaling of the Manganese Recovery Process Using Current Distribution and Potential Simulation Techniques

by Esaú M. Rodríguez Vigueras, Victor E. Reyes Cruz, Felipe M. Galleguillos Madrid, José A. Cobos Murcia, Quinik L. Reyes Morales, Gustavo Urbano Reyes, Marissa Vargas Ramírez, Felipe Legorreta García and Marinka Varas

Metals 2025, 15(5), 562; https://doi.org/10.3390/met15050562 - 20 May 2025

Abstract

Electrolytic metallic manganese (EMM) is used as an alloying metal to provide resistance to abrasion and corrosion. Highly pure EMM is obtained through electrorecovery or electrowinning. Efforts are ongoing to improve the efficiency and profitability of this process, as 85 to 90% of [...] Read more.

Electrolytic metallic manganese (EMM) is used as an alloying metal to provide resistance to abrasion and corrosion. Highly pure EMM is obtained through electrorecovery or electrowinning. Efforts are ongoing to improve the efficiency and profitability of this process, as 85 to 90% of manganese is produced by the mining industry. This study applied computer-aided engineering (CAE) to provide information on the behavior of the potential distribution at the electrodes in cells separated by membranes, which allows for the optimization of the EMM production process. The experimental results obtained galvanostatically for EMM allowed for validation of the simulation parameters. It was determined that the cell with 11 compartments is more suitable compared to cells with fewer compartments, since it has lower oxidation-normalized current density and oxidation potential, which affect the distribution of cathodic potential in the process of obtaining EMM. The simulation highlighted a better distribution of the cathodic and anodic potentials due to the increase in the number of electrodes. This saves time and resources in the design of electrochemical cells with a greater number of compartments. Full article

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

► Show Figures

Graphical abstract

17 pages, 4575 KiB

Open AccessArticle

Effects of TiC Addition on Mechanical Behavior and Cutting Performance of Powder Extrusion Printed Cemented Carbides

by Bisheng Zhong, Dezhi He, Xin Deng and Peishen Ni

Metals 2025, 15(5), 561; https://doi.org/10.3390/met15050561 - 19 May 2025

Abstract

This study addresses the limited research on the mechanical behavior and cutting performance of additive manufactured cemented carbides with high TiC content, which has impeded the rapid development of additive manufacturing in carbide cutting tools. Using powder extrusion printing (PEP) additive manufacturing technology, [...] Read more.

This study addresses the limited research on the mechanical behavior and cutting performance of additive manufactured cemented carbides with high TiC content, which has impeded the rapid development of additive manufacturing in carbide cutting tools. Using powder extrusion printing (PEP) additive manufacturing technology, we successfully fabricated WC-10TiC-12Co and WC-20TiC-12Co carbides with a relative density exceeding 97%. We investigated the effects of TiC content on the mechanical properties and cutting performance of WC-12Co carbide tools. The results show that TiC addition significantly affects the mechanical properties and cutting performance of PEP-processed carbides. Adding 10 wt.% and 20 wt.% TiC increases the Vickers hardness to 1403 HV30 and 1496 HV30, respectively, compared to 1317 HV30 for WC-12Co without TiC. However, TiC addition reduces the flexural strength from 2025 MPa for WC-12Co to 1434 MPa with 10 wt.% TiC and further to 915 MPa with 20 wt.% TiC. Tribological testing indicates that TiC addition reduces the friction coefficient and enhances wear resistance. HT250 cutting tests reveal that TiC addition significantly improves wear resistance and reduces workpiece surface roughness, particularly during longer cutting durations. This study broadens the scope of carbide materials suitable for PEP additive manufacturing. Full article

► Show Figures

Figure 1

Journal Description

Metals

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Further Information

Guidelines

MDPI Initiatives

Follow MDPI