Metals

14 pages, 3909 KiB

Open AccessArticle

Demonstrating In Situ Formation of Globular Microstructure for Thixotropic Printing of EN AW-4043 Aluminum Alloy

by Silvia Marola and Maurizio Vedani

Metals 2025, 15(7), 804; https://doi.org/10.3390/met15070804 - 17 Jul 2025

This study explores the feasibility of generating a globular microstructure in situ during the thixotropic 3D printing of the EN AW-4043 alloy, starting from a conventional cold-rolled wire. Thermodynamic simulations using Thermo-Calc software were first conducted to identify the semi-solid processing window of [...] Read more.

This study explores the feasibility of generating a globular microstructure in situ during the thixotropic 3D printing of the EN AW-4043 alloy, starting from a conventional cold-rolled wire. Thermodynamic simulations using Thermo-Calc software were first conducted to identify the semi-solid processing window of the alloy, based on the evolution of liquid and solid fractions as a function of temperature. Guided by these results, thermal treatments were performed on cold-rolled wires to promote the formation of a globular microstructure. A laboratory-scale printing head prototype was then designed and built to test continuous heating and deposition conditions representative of a thixotropic additive manufacturing process. The results showed that a globular microstructure could be achieved in the cold-rolled EN AW-4043 wires by heating them at 590 °C for 5 min in a static muffle furnace. A similar effect was observed when continuously heating the wire while it flowed through the heated printing head. Preliminary deposition tests confirmed the viability of this approach and demonstrated that thixotropic 3D printing of EN AW-4043 alloy is achievable without the need for pre-globular feedstock. Full article

(This article belongs to the Section Additive Manufacturing)

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35 pages, 6745 KiB

Open AccessArticle

The ESTPHAD Concept: An Optimised Set of Simplified Equations to Estimate the Equilibrium Liquidus and Solidus Temperatures, Partition Ratios, and Liquidus Slopes for Quick Access to Equilibrium Data in Solidification Software Part II: Ternary Isomorphous Equilibrium Phase Diagram

by Gergely Kőrösy, András Roósz and Tamás Mende

Metals 2025, 15(7), 803; https://doi.org/10.3390/met15070803 - 16 Jul 2025

Abstract

In a previous article, an estimation procedure for calculating the liquidus and solidus lines of binary equilibrium phase diagrams was presented. In this article, keeping the thermodynamic basics, the estimation method for the approximate calculation of the liquidus and solidus surfaces of ternary [...] Read more.

In a previous article, an estimation procedure for calculating the liquidus and solidus lines of binary equilibrium phase diagrams was presented. In this article, keeping the thermodynamic basics, the estimation method for the approximate calculation of the liquidus and solidus surfaces of ternary phase diagrams was further developed. It is shown that the procedure has a hierarchical structure, and the ternary functions contain the binary functions. The applicability of the method is checked by calculating the liquidus and solidus surfaces of the Ag-Au-Pd isomorphous ternary equilibrium phase diagram. The application of each level of the developed four-level procedure depends on the data available and the aim. It is shown that in the case of a concentration range close to the base alloy pure element, the liquidus and solidus surfaces of the ternary equilibrium phase diagram can be calculated from the liquidus and solidus functions of the binary equilibrium phase diagrams with a few K errors, which is 0.2 at% at 10 K/at% slope. The equilibrium phase diagrams were available in graphical form, so the data obtained via digitalisation of the diagrams for the calculations was used. The functions describe the slope of the surfaces, and the approximate method developed for the calculation of the partition ratios is also shown. Full article

(This article belongs to the Special Issue Thermodynamic Assessment of Alloy Systems)

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13 pages, 4282 KiB

Open AccessArticle

Cerium Addition Enhances Impact Energy Stability in S355NL Steel by Tailoring Microstructure and Inclusions

by Jiandong Yang, Bijun Xie and Mingyue Sun

Metals 2025, 15(7), 802; https://doi.org/10.3390/met15070802 - 16 Jul 2025

Abstract

S355NL structural steel is extensively employed in bridges, ships, and power station equipment owing to its excellent tensile strength, weldability, and low-temperature toughness. However, pronounced fluctuations in its Charpy impact energy at low temperatures significantly compromise the reliability and service life of critical [...] Read more.

S355NL structural steel is extensively employed in bridges, ships, and power station equipment owing to its excellent tensile strength, weldability, and low-temperature toughness. However, pronounced fluctuations in its Charpy impact energy at low temperatures significantly compromise the reliability and service life of critical components. In this study, vacuum-induction-melted ingots of S355NL steel containing 0–0.086 wt.% rare earth cerium were prepared. The effects of Ce on microstructures, inclusions, and impact toughness were systematically investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and Charpy V-notch testing. The results indicate that appropriate Ce additions (0.0011–0.0049 wt.%) refine the average grain size from 5.27 μm to 4.88 μm, reduce the pearlite interlamellar spacing from 204 nm to 169 nm, and promote the transformation of large-size Al₂O₃-MnS composite inclusions into fine, spherical, Ce-rich oxysulfides. Charpy V-notch tests at –50 °C reveal that 0.0011 wt.% Ce enhances both longitudinal (269.7 J) and transverse (257.4 J) absorbed energies while minimizing anisotropy (E_t/E_l = 1.01). Conversely, excessive Ce addition (0.086 wt.%) leads to coarse inclusions and deteriorates impact performance. These findings establish an optimal Ce window (0.0011–0.0049 wt.%) for microstructural and inclusion engineering to enhance the low-temperature impact toughness of S355NL steel. Full article

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16 pages, 5637 KiB

Open AccessArticle

Optimizing High-Al₂O₃ Limonite Pellet Performance: The Critical Role of Basicity in Consolidation and Reduction

by Yufeng Guo, Yixi Zhang, Feng Chen, Shuai Wang, Lingzhi Yang, Yanqin Xie and Xinyao Xia

Metals 2025, 15(7), 801; https://doi.org/10.3390/met15070801 - 16 Jul 2025

Abstract

With the gradual depletion of high-quality iron ore resources, global steel enterprises have shifted their focus to low-grade, high-impurity iron ores. Using low-grade iron ore to produce pellets for blast furnaces is crucial for companies to control production costs and diversify raw material [...] Read more.

With the gradual depletion of high-quality iron ore resources, global steel enterprises have shifted their focus to low-grade, high-impurity iron ores. Using low-grade iron ore to produce pellets for blast furnaces is crucial for companies to control production costs and diversify raw material sources. However, producing qualified pellets from limonite and other low-grade iron ores remains highly challenging. This study investigates the mechanism by which basicity affects the consolidation and reduction behavior of high-Al₂O₃ limonite pellets from a thermodynamic perspective. As the binary basicity of the pellets increased from 0.01 under natural conditions to 1.2, the compressive strength of the roasted pellets increased from 1100 N/P to 5200 N/P. The enhancement in basicity led to an increase in the amount of low-melting-point calcium ferrite in the binding phase, which increased the liquid phase in the pellets, thereby strengthening the consolidation. CaO infiltrated into large-sized iron particles and reacted with Al and Si elements, segregating the contiguous large-sized iron particles and encapsulating them with liquid-phase calcium ferrite. Calcium oxide reacts with the Al and Si elements in large hematite particles, segmenting them and forming liquid calcium ferrite that encapsulates the particles. Additionally, this study used thermodynamic analysis to characterize the influence of CaO on aluminum elements in high-aluminum iron ore pellets. Adding CaO boosted the liquid phase’s ability to incorporate aluminum, lessening the inhibition by high-melting-point aluminum elements of hematite recrystallization. During the reduction process, pellets with high basicity exhibited superior reduction performance. Full article

(This article belongs to the Special Issue Steelmaking and Ironmaking: Fundamental Research to Technology Innovation)

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14 pages, 5155 KiB

Open AccessArticle

Erosion of AISI 4340 and AISI 8620 Steels with High Ductility Caused by SiC Particles

by Juan R. Laguna-Camacho, Ezequiel A. Gallardo-Hernández, Manuel Vite-Torres, Celia M. Calderón-Ramón, Víctor Velázquez-Martínez, Silvia M. Sánchez-Yáñez and Karla I. Zermeño-De Lojo

Metals 2025, 15(7), 800; https://doi.org/10.3390/met15070800 - 16 Jul 2025

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Abstract

In this study, solid particle erosion tests were conducted to evaluate the resistance of AISI 4340 (EN24) and 8620 alloy steels against silicon carbide (SiC). These steels were selected due to their high hardness, yield strength (σ_y), ultimate tensile strength (σ [...] Read more.

In this study, solid particle erosion tests were conducted to evaluate the resistance of AISI 4340 (EN24) and 8620 alloy steels against silicon carbide (SiC). These steels were selected due to their high hardness, yield strength (σ_y), ultimate tensile strength (σ_uts) and elongation (%), which are significant parameters, influencing wear resistance. An erosion rig based on the ASTM G76-95 standard was used to perform the testing. Tests were carried out using different impact angles, 30°, 45°, 60° and 90°, with a particle velocity of 24 ± 2 m/s. The abrasive flow rate was 0.7 ± 0.5 g/min and the temperature was between 35 °C and 40 °C. Characterization techniques such as SEM were employed to identify the chemical composition of AISI 4340 and AISI 8620 steels and optical microscopy to determine the morphology of SiC abrasive particles. In addition, the SiC particle size was between 350 and 450 µm; it was determined by the particle size distribution technique. SEM micrographs were obtained to classify the wear mechanisms, characterized by micro-cutting, micro-ploughing, grooves, pitting actions and embedded particles on the surface at 30° and 90°. The results showed that AISI 8620 steel exhibited higher erosion resistance than AISI 4340 steel. Finally, AFM was used to evaluate the roughness variations before and after erosion tests, specifically in the central zone of the wear scars at 30° and 90° for both materials. Full article

(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)

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17 pages, 343 KiB

Open AccessReview

Recovery of Tungsten from Raw and Secondary Materials Using Hydrometallurgical Processing

by Francisco Jose Alguacil and Manuel Alonso

Metals 2025, 15(7), 799; https://doi.org/10.3390/met15070799 - 15 Jul 2025

Viewed by 91

Abstract

As in the case with other metals, tungsten is an element with a number of uses in different fields, which is why its recovery from both primary and secondary materials continues to be of great interest. Various hydrometallurgical processes, considered as unit operations, [...] Read more.

As in the case with other metals, tungsten is an element with a number of uses in different fields, which is why its recovery from both primary and secondary materials continues to be of great interest. Various hydrometallurgical processes, considered as unit operations, can be used for the recovery, separation and concentration of tungsten from any source, with ease of scaling-up a potential factor when considering the best process for practical use. The present work reviewed investigations into the use of such unit operations for the recovery of tungsten which were published during 2024 and the first half of 2025. Because most if not all of these investigations were conducted on a laboratory scale, there is still much room for improvement before deciding on the best option for tungsten recovery. In all cases, however, this recovery is based on a series of steps from leaching to separation technologies (ion exchange resins, liquid–liquid extraction, etc.) to the tungsten end-product. Full article

(This article belongs to the Special Issue Tungsten and Tungsten Alloys)

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25 pages, 14812 KiB

Open AccessArticle

The Effect of Yttrium Addition on the Solidification Microstructure and Sigma Phase Precipitation Behavior of S32654 Super Austenitic Stainless Steel

by Jun Xiao, Geng Tian, Di Wang, Shaoguang Yang, Kuo Cao, Jianhua Wei and Aimin Zhao

Metals 2025, 15(7), 798; https://doi.org/10.3390/met15070798 - 15 Jul 2025

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Abstract

This study focuses on S32654 super austenitic stainless steel (SASS) and systematically characterizes the morphology of the sigma (σ) phase and the segregation behavior of alloying elements in its as-cast microstructure. High-temperature confocal scanning laser microscopy (HT-CSLM) was employed to investigate the effect [...] Read more.

This study focuses on S32654 super austenitic stainless steel (SASS) and systematically characterizes the morphology of the sigma (σ) phase and the segregation behavior of alloying elements in its as-cast microstructure. High-temperature confocal scanning laser microscopy (HT-CSLM) was employed to investigate the effect of the rare earth element yttrium (Y) on the solidification microstructure and σ phase precipitation behavior of SASS. The results show that the microstructure of SASS consists of austenite dendrites and interdendritic eutectoid structures. The eutectoid structures mainly comprise the σ phase and the γ₂ phase, exhibiting lamellar or honeycomb-like morphologies. Regarding elemental distribution, molybdenum displays a “concave” distribution pattern within the dendrites, with lower concentrations at the center and higher concentrations at the sides; when Mo locally exceeds beyond a certain threshold, it easily induces the formation of eutectoid structures. Mo is the most significant segregating element, with a segregation ratio as high as 1.69. The formation mechanism of the σ phase is attributed to the solid-state phase transformation of austenite (γ → γ₂ + σ). In the late stages of solidification, the concentration of chromium and Mo in the residual liquid phase increases, and due to insufficient diffusion, there are significant compositional differences between the interdendritic regions and the matrix. The enriched Cr and Mo cause the interdendritic austenite to become supersaturated, leading to solid-state phase transformation during subsequent cooling, thereby promoting σ phase precipitation. The overall phase transformation process can be summarized as L → L + γ → γ → γ + γ₂ + σ. Y microalloying has a significant influence on the solidification process. The addition of Y increases the nucleation temperature of austenite, raises nucleation density, and refines the solidification microstructure. However, Y addition also leads to an increased amount of eutectoid structures. This is primarily because Y broadens the solidification temperature range of the alloy and prolongs grain growth perio, which aggravates the microsegregation of elements such as Cr and Mo. Moreover, Y raises the initial precipitation temperature of the σ phase and enhances atomic diffusion during solidification, further promoting σ phase precipitation during the subsequent eutectoid transformation. Full article

(This article belongs to the Special Issue Synthesis, Processing and Applications of New Forms of Metals)

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19 pages, 1907 KiB

Open AccessArticle

Enhancing Aluminum Alloy Properties Through Low Pressure Forging: A Comprehensive Study on Heat Treatments

by Silvia Cecchel and Giovanna Cornacchia

Metals 2025, 15(7), 797; https://doi.org/10.3390/met15070797 - 15 Jul 2025

Viewed by 67

Abstract

The weight reduction is a key objective in modern engineering, particularly in the automotive industry, to enhance vehicle performance and reduce the carbon footprint. In this context aluminum alloys are widely used in structural automotive applications, often through forging processes that enhance mechanical [...] Read more.

The weight reduction is a key objective in modern engineering, particularly in the automotive industry, to enhance vehicle performance and reduce the carbon footprint. In this context aluminum alloys are widely used in structural automotive applications, often through forging processes that enhance mechanical properties compared to the results for casting. However, the high cost of forging can limit its economic feasibility. Low pressure forging (LPF) combines the benefits of casting and forging, employing controlled pressure to fill the mold cavity and improve metal purity. This study investigates the effectiveness of the LPF process in optimizing the mechanical properties of AlSi7Mg aluminum alloy by evaluating the influence of three different magnesium content levels. The specimens underwent T6 heat treatment (solubilization treatment followed by artificial aging), with varying aging times and temperatures. Microstructural analysis and tensile tests were conducted to determine the optimal conditions for achieving superior mechanical strength, contributing to the design of lightweight, high-performance components for advanced automotive applications. The most promising properties were achieved with a T6 treatment consisting of solubilization at 540 °C for 6 h followed by aging at 180 °C for 4 h, resulting in mechanical properties of σ_y 280 MPa, σ_m 317 MPa, and A% 3.5%. Full article

(This article belongs to the Special Issue Advances in Lightweight Alloys, 2nd Edition)

13 pages, 3560 KiB

Open AccessArticle

Experimental Study on the Parameter Optimization of an Ultra-High-Pressure Water Jet for Grade-A Marine Steel Based on Surface Roughness

by Wuyang Shan, Yupeng Cao, Weidong Shi, Zhengang Wang, Qingbo Zhang, Yongfei Yang and Rui Zhou

Metals 2025, 15(7), 796; https://doi.org/10.3390/met15070796 - 15 Jul 2025

Viewed by 108

Abstract

The selection of process parameters for an ultra-high-pressure water jet directly affects the adhesion ability of the subsequent coating on the ship’s surface. This study investigates the effect of jet pressure, standoff distance, and nozzle traverse speed on the surface roughness of grade-A [...] Read more.

The selection of process parameters for an ultra-high-pressure water jet directly affects the adhesion ability of the subsequent coating on the ship’s surface. This study investigates the effect of jet pressure, standoff distance, and nozzle traverse speed on the surface roughness of grade-A marine steel, aiming to optimize the process parameters and improve the quality of surface treatment. Based on single-factor experiments and orthogonal experiments, a three-factor, three-level experimental design was employed, considering jet pressure, standoff distance, and nozzle traverse speed. Scanning electron microscopy (SEM) and a confocal microscope were used to analyze the surface morphology and roughness of grade-A marine steel. The experimental results proved that surface roughness exhibited a nonlinear relationship with jet pressure, initially increasing and then decreasing as pressure rose. Conversely, surface roughness showed negative correlations with both standoff distance and nozzle traverse speed, progressively decreasing with increases in these parameters. Through hierarchical analysis, the effect hierarchy of the three factors on surface roughness was determined as follows: jet pressure > standoff distance > nozzle traverse speed. Parametric optimization revealed that a jet pressure of 150 MPa, a standoff distance of 25 mm, and a nozzle traverse speed of 180 mm/min collectively yielded a peak surface roughness of 62.549 μm. This value aligns with the pre-coating surface preparation standards for grade-A marine steel substrates, ensuring optimal adhesion for subsequent anti-corrosion treatments. Full article

(This article belongs to the Special Issue Fabricating Advanced Metallic Materials)

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17 pages, 3800 KiB

Open AccessArticle

Characterizing the Substructural Changes in Metals by Microindentation and Various Numerical Approaches

by János György Bátorfi and Jurij J. Sidor

Metals 2025, 15(7), 795; https://doi.org/10.3390/met15070795 - 14 Jul 2025

Viewed by 70

Abstract

This contribution compares various theories dealing with the assessment of dislocation density in metals subjected to different straining levels. The paper examines both substructure development and the evolution of dislocation densities in 1xxx, 5xxx, and 6xxx Al alloys. Barlat’s dislocation model, Kocks–Mecking–Estrin (K-M-E) [...] Read more.

This contribution compares various theories dealing with the assessment of dislocation density in metals subjected to different straining levels. The paper examines both substructure development and the evolution of dislocation densities in 1xxx, 5xxx, and 6xxx Al alloys. Barlat’s dislocation model, Kocks–Mecking–Estrin (K-M-E) theory, and Kubin–Estrin (K-E) type modeling approaches were analyzed. The dislocation model parameters were determined from the microindentation profiles for the rolled Al alloys. It was shown that a strong correlation exists between the K-E and K-M-E models, confirming their reliability in describing the relationship between strain, stress, and dislocation density. These numerical approaches effectively capture the evolution of dislocation density with strain, making them suitable for the analysis of the accumulation of stored energy during deformation. The development of substructure during straining was inferred from the microindentation experiments, and the resulting dependencies tended to align with the characteristic curve observed in various metals. Full article

(This article belongs to the Special Issue Formation, Microstructure, and Properties of Light Alloys)

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18 pages, 2268 KiB

Open AccessArticle

Effects of a Novel Mechanical Vibration Technology on the Internal Stress Distribution and Macrostructure of Continuously Cast Billets

by Shuai Liu, Jianliang Zhang, Hui Zhang and Minglin Wang

Metals 2025, 15(7), 794; https://doi.org/10.3390/met15070794 - 14 Jul 2025

Viewed by 131

Abstract

In this paper, a new mechanical vibration technology applied to continuous casting production is studied, which is used to break the dendrite at the solidification front, expand the equiaxed dendrite zone, and improve the center quality of the billet. The exciting force of [...] Read more.

In this paper, a new mechanical vibration technology applied to continuous casting production is studied, which is used to break the dendrite at the solidification front, expand the equiaxed dendrite zone, and improve the center quality of the billet. The exciting force of this vibration technology is provided by a new type of vibration equipment (Vibration roll) independently developed and designed. Firstly, an investigation is conducted into the impacts of vibration acceleration, vibration frequency, and the contact area between the Vibration roll (VR) and the billet surface on the internal stress distribution within the billet shell, respectively. Secondly, the billet with and without vibration treatment was sampled and analyzed through industrial tests. The results show that the area ratio of equiaxed dendrites in transverse specimens treated with vibration technology was 11.96%, compared to 6.55% in untreated specimens. Similarly, for longitudinal samples, the linear ratio of equiaxed dendrites was observed to be 34.56% in treated samples and 22.95% in untreated samples. Compared to the specimens without mechanical vibration, the billet treated with mechanical vibration exhibits an increase in the area ratio and linear ratio of equiaxed dendrite ratio by 5.41% and 11.61%, respectively. Moreover, the probability of bridging at the end of solidification of the billet treated by vibration technology was significantly reduced, and the central porosity and shrinkage cavities of the billet were significantly improved. This study provides the first definitive evidence that the novel mechanical vibration technology can enhance the quality of the billet during the continuous casting process. Full article

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33 pages, 20199 KiB

Open AccessReview

Composition Optimization in Alloy Design for Nickel-Based Single Crystal Superalloy: A Review

by Yu Zhou, Xinbao Zhao, Yunpeng Fan, Quanzhao Yue, Wanshun Xia, Qinghai Pan, Yuan Cheng, Weiqi Li, Yuefeng Gu and Ze Zhang

Metals 2025, 15(7), 793; https://doi.org/10.3390/met15070793 - 13 Jul 2025

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Abstract

This article presents a review of the composition optimization progress of nickel-based single crystal (SC) superalloy design in recent years in order to obtain better high-temperature performance for the development of the aviation industry. The influence of alloying elements on the creep resistance, [...] Read more.

This article presents a review of the composition optimization progress of nickel-based single crystal (SC) superalloy design in recent years in order to obtain better high-temperature performance for the development of the aviation industry. The influence of alloying elements on the creep resistance, microstructure characteristics, oxidation resistance, castability, density, and cost of superalloys is analyzed and discussed. In order to obtain better high-temperature performance, the content of refractory elements (Ta + Re + W + Mo) and Co was increased gradually. The addition of Ru was added in the fourth-generation nickel-based SC superalloy to stabilize the microstructures and suppress the precipitation of the topologically close-packed (TCP) phase. However, the content of the antioxidant element Cr significantly decreased, while the synergistic effect of Al, Cr, and Ta received more attention. Therefore, synergistic effects should also receive more attention to meet the practical needs of reducing the content of refractory elements to reduce costs and density in future single crystal alloy designs without compromising critical performance. Full article

(This article belongs to the Special Issue Advances in Lightweight Alloys, 2nd Edition)

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16 pages, 3348 KiB

Open AccessArticle

Response and Failure Behavior of Square Tubes with Varying Outer Side Lengths Under Cyclic Bending in Different Directions

by Chin-Mu Lin, Min-Cheng Yu and Wen-Fung Pan

Metals 2025, 15(7), 792; https://doi.org/10.3390/met15070792 - 13 Jul 2025

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Abstract

This paper primarily investigates the response and failure behavior of 6063-T5 aluminum alloy square tubes with varying outer side lengths under symmetric curvature-controlled cyclic bending in different bending directions. The response is characterized by the moment–curvature relationship and the variation in the outer [...] Read more.

This paper primarily investigates the response and failure behavior of 6063-T5 aluminum alloy square tubes with varying outer side lengths under symmetric curvature-controlled cyclic bending in different bending directions. The response is characterized by the moment–curvature relationship and the variation in the outer side length with respect to curvature, whereas failure is characterized by the relationship between the controlled curvature and the number of cycles required to initiate buckling. The outer side lengths studied are 20 mm, 30 mm, 40 mm, and 50 mm, and the bending directions considered are 0°, 22.5°, and 45°. The moment–curvature curves exhibited cyclic hardening, and stable loops were formed for all outer side lengths and bending directions. An increase in the outer side length resulted in a higher peak bending moment, while a greater bending direction led to a slight increase in the peak bending moment. For a fixed bending direction, the curves representing the variation of the outer side length (defined as the change in length divided by the original length) with respect to curvature displayed symmetry, serrated features, and an overall increasing trend as the number of cycles increased, irrespective of the specific outer side length. In addition, increasing either the outer side length or altering the bending direction led to a larger variation in the outer side length. As for the relationship between curvature and the number of cycles required to initiate buckling, the data for each bending direction and each of the four outer side lengths formed distinct straight lines on a double-logarithmic plot. Based on the experimental observations, empirical equations were developed to characterize these relationships. These equations were then used to predict the experimental data and showed excellent agreement with the measured results. Full article

(This article belongs to the Special Issue Mechanical Structure Damage of Metallic Materials)

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16 pages, 8314 KiB

Open AccessArticle

Effect of the Heat Affected Zone Hardness Reduction on the Tensile Properties of GMAW Press Hardening Automotive Steel

by Alfredo E. Molina-Castillo, Enrique A. López-Baltazar, Francisco Alvarado-Hernández, Salvador Gómez-Jiménez, J. Roberto Espinosa-Lumbreras, José Jorge Ruiz Mondragón and Víctor H. Baltazar-Hernández

Metals 2025, 15(7), 791; https://doi.org/10.3390/met15070791 - 13 Jul 2025

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Abstract

An ultra-high-strength press-hardening steel (PHS) and a high-strength dual-phase steel (DP) were butt-joined by the gas metal arc welding (GMAW) process, aiming to assess the effects of a high heat input welding process on the structure-property relationship and residual stress. The post-weld microstructure, [...] Read more.

An ultra-high-strength press-hardening steel (PHS) and a high-strength dual-phase steel (DP) were butt-joined by the gas metal arc welding (GMAW) process, aiming to assess the effects of a high heat input welding process on the structure-property relationship and residual stress. The post-weld microstructure, the microhardness profile, the tensile behavior, and the experimentally obtained residual stresses (by x-ray diffraction) of the steels in dissimilar (PHS-DP) and similar (PHS-PHS, DP-DP) pair combinations have been analyzed. Results indicated that the ultimate tensile strength (UTS) of the dissimilar pair PHS-DP achieves a similar strength to the DP-DP joint, whereas the elongation was similar to that of the PHS-PHS weldment. The failure location of the tensile specimens was expected and systematically observed at the tempered and softer sub-critical heat-affected zone (SC-HAZ) in all welded conditions. Compressive residual stresses were consistently observed along the weldments in all specimens; the more accentuated negative RS were measured in the PHS joint attributed to the higher volume fraction of martensite; furthermore, the negative RS measured in the fusion zone (FZ) could be well correlated to weld restraint due to the sheet anchoring during the welding procedure, despite the presence of predominant ferrite and pearlite microstructures. Full article

(This article belongs to the Special Issue Welding and Joining of Advanced High-Strength Steels (2nd Edition))

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24 pages, 6554 KiB

Open AccessArticle

Modeling Mechanical Properties of Industrial C-Mn Cast Steels Using Artificial Neural Networks

by Saurabh Tiwari, Seongjun Heo, Nokeun Park and Nagireddy Gari S. Reddy

Metals 2025, 15(7), 790; https://doi.org/10.3390/met15070790 - 12 Jul 2025

Viewed by 135

Abstract

This study develops a comprehensive artificial neural network (ANN) model for predicting the mechanical properties of carbon–manganese cast steel, specifically, the yield strength (YS), tensile strength (TS), elongation (El), and reduction of area (RA), based on the chemical composition (16 alloying elements) and [...] Read more.

This study develops a comprehensive artificial neural network (ANN) model for predicting the mechanical properties of carbon–manganese cast steel, specifically, the yield strength (YS), tensile strength (TS), elongation (El), and reduction of area (RA), based on the chemical composition (16 alloying elements) and heat treatment parameters. The neural network model, employing a 20-44-44-4 architecture and trained on 400 samples from an industrial dataset of 500 samples, achieved 90% of test predictions within a 5% deviation from actual values, with mean prediction errors of 3.45% for YS and 4.9% for %EL. A user-friendly graphical interface was developed to make these predictive capabilities accessible, without requiring programming expertise. Sensitivity analyses revealed that increasing the copper content from 0.05% to 0.2% enhanced the yield strength from 320 to 360 MPa while reducing the ductility, whereas niobium functioned as an effective grain refiner, improving both the strength and ductility. The combined effects of carbon and manganese demonstrated complex synergistic behavior, with the yield strength varying between 280 and 460 MPa and the tensile strength ranging from 460 to 740 MPa across the composition space. Optimal strength–ductility balance was achieved at moderate compositions of 1.0–1.2 wt% Mn and 0.20–0.24 wt% C. The model provides an efficient alternative to costly experimental trials for optimizing C-Mn steels, with prediction errors consistently below 6% compared with 8–20% for traditional empirical methods. This approach establishes quantitative guidelines for designing complex multi-element alloys with targeted mechanical properties, representing a significant advancement in computational material engineering for industrial applications. Full article

(This article belongs to the Special Issue Advances in Constitutive Modeling for Metals and Alloys)

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24 pages, 11312 KiB

Open AccessArticle

Effect of Thermomechanical Processing on Porosity Evolution and Mechanical Properties of L-PBF AISI 316L Stainless Steel

by Patrik Petroušek, Róbert Kočiško, Andrea Kasperkevičová, Dávid Csík and Róbert Džunda

Metals 2025, 15(7), 789; https://doi.org/10.3390/met15070789 - 12 Jul 2025

Viewed by 174

Abstract

Thermomechanical processing has a significant impact on the porosity and mechanical properties of AISI 316L stainless steel produced by laser powder bed fusion (L-PBF). This work evaluated the effect of three heat treatment conditions: as-built (HT0), annealed at 650 °C for 3 h [...] Read more.

Thermomechanical processing has a significant impact on the porosity and mechanical properties of AISI 316L stainless steel produced by laser powder bed fusion (L-PBF). This work evaluated the effect of three heat treatment conditions: as-built (HT0), annealed at 650 °C for 3 h with air cooling (HT1), and annealed at 1050 °C for 1 h followed by water quenching (HT2), combined with cold and hot rolling at different strain levels. The most pronounced improvement was observed after 20% hot rolling followed by water quenching (HR + WQ), which reduced porosity to 0.05% and yielded the most spherical pores, with a circularity factor (

f_{c i r c l e}

) of 0.90 and an aspect ratio (AsR) of 1.57. At elevated temperatures, the matrix becomes more pliable, which promotes pore closure and helps reduce stress concentrations. On the other hand, applying heat treatment without causing deformation resulted in the pores growing and increasing porosity in the build direction. The fractography supported these findings, showing a transition from brittle to more ductile fracture surfaces. Heat treatment combined with plastic deformation effectively reduced internal defects and improved both structural integrity and strength. Full article

(This article belongs to the Special Issue Metal Forming and Additive Manufacturing)

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22 pages, 16747 KiB

Open AccessArticle

Development of a Technique for Toughness Estimation in Dual-Phase Steels Using Representative Volume Elements

by Amin Latifi Vanjani, Hari M. Simha and Alexander Bardelcik

Metals 2025, 15(7), 788; https://doi.org/10.3390/met15070788 - 11 Jul 2025

Viewed by 109

Abstract

A novel approach to estimating the absorbed energy (toughness) in a uniaxial tensile test with only knowledge of the microstructure is presented. The flow behavior of each Dual-Phase (DP) steel grade is predicted using idealized Representative Volume Elements (RVEs) up to uniform elongation. [...] Read more.

A novel approach to estimating the absorbed energy (toughness) in a uniaxial tensile test with only knowledge of the microstructure is presented. The flow behavior of each Dual-Phase (DP) steel grade is predicted using idealized Representative Volume Elements (RVEs) up to uniform elongation. To estimate the flow behavior beyond uniform elongation, the stress-modified fracture strain in a non-local damage model was implemented in Abaqus. Damage parameters were calibrated using Finite Element (FE) simulations of purely ferritic tensile specimens. The damage parameters remained unchanged, except for the coefficient of triaxiality. This coefficient was adjusted based on the average triaxiality of ferrite elements at the instability point of the uniaxially loaded RVEs for each DP steel grade. The proposed approach comprises two steps: micron-sized RVEs to predict the flow behavior up to the point of uniform elongation and the average triaxiality and full-scale tensile-test simulations to predict the rest of the curves. The results show that the damage parameters calibrated for high-strain ferrite effectively estimate the absorbed energy during failure in tension tests. This approach is also geometry-independent; varying the geometry of the tensile specimen, including miniature or notched specimens, still yields predicted absorbed energies that are in good agreement with the experimental results. Full article

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12 pages, 13899 KiB

Open AccessArticle

The Role of Pores in the Cavitation Erosion of Additively Manufactured Metal: An In Situ Study

by Yuan Song, Zhenhua Wang and Bingyang Ma

Metals 2025, 15(7), 787; https://doi.org/10.3390/met15070787 - 11 Jul 2025

Viewed by 171

Abstract

Additively manufactured (AM) parts have been applied in many areas with the risk of cavitation erosion (CE), and pores are common defects in AM metals. However, the role of pores in CE is still unclear, and a systematic investigation is needed. In this [...] Read more.

Additively manufactured (AM) parts have been applied in many areas with the risk of cavitation erosion (CE), and pores are common defects in AM metals. However, the role of pores in CE is still unclear, and a systematic investigation is needed. In this study, 316L stainless steel was selected as a model material and produced using laser powder bed fusion; the porosity was 6.4%. The morphological evolution of various pores during CE was investigated via electron backscatter diffraction and scanning electron microscopy. It was found that material removal easily occurred around large polygonal pores. The critical size for large polygonal pores was estimated to be between 13 and 20 μm. For narrow pores, concavity first appeared around the pores during CE, and then the narrow pores closed. Small spherical pores with sizes of 3–9 μm showed strong resistance to CE, and no damage occurred within the 60 min CE period. The main reason that different pores played different roles in CE was analyzed. Finally, factors for improving the CE resistance of AM metals were suggested. The research results are helpful for understanding the CE behaviors of AM metals and porous materials. Full article

(This article belongs to the Section Metal Failure Analysis)

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22 pages, 6902 KiB

Open AccessArticle

Numerical Analysis of Aspect Ratio Effects on the Mechanical Behavior of Perforated Steel Plates

by Thiago da Silveira, Eduardo Araujo Crestani, Elizaldo Domingues dos Santos and Liércio André Isoldi

Metals 2025, 15(7), 786; https://doi.org/10.3390/met15070786 - 11 Jul 2025

Viewed by 122

Abstract

Thin plates are commonly used in mechanical structures such as ship hulls, offshore platforms, aircraft, automobiles, and bridges. When subjected to in-plane compressive loads, these structures may experience buckling. In some applications, perforations are introduced, altering membrane stress distribution and buckling behavior. This [...] Read more.

Thin plates are commonly used in mechanical structures such as ship hulls, offshore platforms, aircraft, automobiles, and bridges. When subjected to in-plane compressive loads, these structures may experience buckling. In some applications, perforations are introduced, altering membrane stress distribution and buckling behavior. This study investigates the elasto-plastic buckling behavior of perforated plates using the Finite Element Method (FEM), Constructal Design (CD), and Exhaustive Search (ES) techniques. Simply supported thin rectangular plates with central elliptical perforations were analyzed under biaxial elasto-plastic buckling. Three shapes of holes were considered—circular, horizontal elliptical, and vertical elliptical—along with sixteen aspect ratios and two different materials. Results showed that higher yield stress leads to higher ultimate stress for perforated plates. Regardless of material, plates exhibited a similar trend: ultimate stress decreased as the aspect ratio dropped from 1.00 to around 0.40 and then increased from 0.35 to 0.25. A similar pattern was observed in the stress components along both horizontal (x) and vertical (y) directions, once the y-component became considerably higher than the x-component for the same range of 0.40 to 0.25. For longer plates, in general, the vertical elliptical hole brings more benefits in structural terms, due to the facility in the distribution of y-components of stress. Full article

(This article belongs to the Special Issue Fracture Mechanics of Metals (2nd Edition))

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27 pages, 21183 KiB

Open AccessArticle

Fracture Initiation in Aluminum Alloys Under Multiaxial Loading at Various Low Strain Rates

by Mehmet Haskul and Eray Arslan

Metals 2025, 15(7), 785; https://doi.org/10.3390/met15070785 - 11 Jul 2025

Viewed by 191

Abstract

The initiation of ductile fractures in medium-strength AW5754 and high-strength AW6082 aluminum alloys at different quasi-static strain rates and under multiaxial stress states was investigated through a series of tensile tests using various specimen geometries. The sensitivity of the stress triaxiality locus to [...] Read more.

The initiation of ductile fractures in medium-strength AW5754 and high-strength AW6082 aluminum alloys at different quasi-static strain rates and under multiaxial stress states was investigated through a series of tensile tests using various specimen geometries. The sensitivity of the stress triaxiality locus to variations in the loading rate was examined for these two aluminum alloy families. Fractographic and elemental analyses were also conducted via SEM and EDS. Numerical simulations based on the finite element method (FEM) were performed using ABAQUS/Standard to determine the actual stress triaxialities and the equivalent plastic strains at fracture. The numerical approach was validated by comparing the simulation results with the experimental findings. These simulations facilitated the generation of a stress triaxiality locus through a curve-fitting process. Among the considered fitting functions, an exponential function was selected as it provided the most accurate relation between the equivalent plastic strain at fracture and the corresponding stress state across different strain rates. The results reveal different strain rate dependencies for the two alloys within a very low strain rate range. The resulting stress triaxiality loci provide a valuable tool for predicting fracture strains and for more accurately evaluating stress states. Overall, the findings of this study significantly advance the understanding of the fracture initiation behavior of aluminum alloys under multiaxial loading conditions and their sensitivity to various quasi-static loading rates. Full article

(This article belongs to the Special Issue Research on Mechanical Properties, Deformation, and Microstructures of Metallic Materials)

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19 pages, 2167 KiB

Open AccessReview

Grain Boundary Engineering for Reversible Zn Anodes in Rechargeable Aqueous Zn-Ion Batteries

by Yu-Xuan Liu, Jun-Zhe Wang, Lei Cao, Hao Wang, Zhen-Yu Cheng, Li-Feng Zhou and Tao Du

Metals 2025, 15(7), 784; https://doi.org/10.3390/met15070784 - 11 Jul 2025

Viewed by 202

Abstract

Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered significant research attention in the energy storage field owing to their inherent safety, cost-effectiveness, and environmental sustainability. Nevertheless, critical challenges associated with zinc anodes—including dendrite formation, hydrogen evolution corrosion, and mechanical degradation—substantially impede their practical implementation. [...] Read more.

Rechargeable aqueous zinc-ion batteries (AZIBs) have garnered significant research attention in the energy storage field owing to their inherent safety, cost-effectiveness, and environmental sustainability. Nevertheless, critical challenges associated with zinc anodes—including dendrite formation, hydrogen evolution corrosion, and mechanical degradation—substantially impede their practical implementation. Grain boundary engineering (GBE) emerges as an innovative solution for zinc anode optimization through the precise regulation of grain boundary density, crystallographic orientation, and chemical states in metallic materials. This study comprehensively investigates the fundamental mechanisms and application prospects of GBE in zinc-based anodes, providing pivotal theoretical insights and technical methodologies for designing highly stable electrode architectures. The findings are expected to promote the development of aqueous zinc batteries toward a high energy density and long cycle life. Full article

(This article belongs to the Special Issue Corrosion Damage Behavior and Mechanisms of Advanced Functional Metallic Materials)

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17 pages, 4357 KiB

Open AccessArticle

Rotational Bending Fatigue Crack Initiation and Early Extension Behavior of Runner Blade Steels in Air and Water Environments

by Bing Xue, Yongbo Li, Wanshuang Yi, Wen Li and Jiangfeng Dong

Metals 2025, 15(7), 783; https://doi.org/10.3390/met15070783 - 11 Jul 2025

Viewed by 186

Abstract

This study provides a comprehensive analysis of the fatigue cracking behavior of super martensitic stainless steel in air and water environments, highlighting the critical influence of environmental factors on its mechanical properties. By examining the distribution of fatigue test data, the Weibull three-parameter [...] Read more.

This study provides a comprehensive analysis of the fatigue cracking behavior of super martensitic stainless steel in air and water environments, highlighting the critical influence of environmental factors on its mechanical properties. By examining the distribution of fatigue test data, the Weibull three-parameter model was identified as the most accurate descriptor of fatigue life data in both environments. Key findings reveal that, in air, cracks predominantly propagate along the densest crystallographic planes, whereas, in water, corrosive media significantly accelerate crack initiation and propagation, reducing fatigue resistance, creating more tortuous crack paths, and inducing microvoids and secondary cracks at the crack tip. These corrosive effects adversely alter the material’s microstructure, profoundly impacting fatigue life and crack propagation rates. The insights gained from this research are crucial for understanding the performance of super martensitic stainless steel in aqueous environments, offering a reliable basis for its engineering applications and contributing to the development of more effective design and maintenance strategies. Full article

(This article belongs to the Special Issue Microstructure, Deformation and Fatigue Behavior in Metals and Alloys)

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14 pages, 467 KiB

Open AccessArticle

Dominant Role of Temperature in Drying Kinetics of Magnetite Pellet: Experimental and Modeling Study

by Xunrui Liu, Manman Lu and Hanquan Zhang

Metals 2025, 15(7), 782; https://doi.org/10.3390/met15070782 - 10 Jul 2025

Viewed by 158

Abstract

Natural magnetite ore is commonly used to produce oxidized pellets as the raw material for blast furnace ironmaking. The drying of green pellets significantly affects the quality of oxidized pellets. However, the drying process in the traveling grate cannot be directly analyzed. To [...] Read more.

Natural magnetite ore is commonly used to produce oxidized pellets as the raw material for blast furnace ironmaking. The drying of green pellets significantly affects the quality of oxidized pellets. However, the drying process in the traveling grate cannot be directly analyzed. To address this issue, in this study the influences of the drying medium temperature, medium velocity, and pellet diameter on the moisture removal, as well as the drying kinetics of the natural magnetite oxidized pellets were investigated. Orthogonal experimental results indicated that the drying medium temperature had the most significant effect on the drying rate, followed by the medium velocity, while the interaction between the pellet diameter and temperature had a minor influence. Drying kinetic model fitting revealed that the drying process followed a modified Page model (III). Model validation demonstrated that the experimental measurements closely aligned with the theoretical predictions, confirming that the Page model (III) accurately predicted the effects of the drying temperature and medium velocity on the pellet moisture content. Higher drying temperatures further improved the prediction accuracy. The findings provide valuable insights for analyzing and optimizing the drying process of the natural magnetite oxidized pellets in the industrial traveling grate systems. Full article

(This article belongs to the Special Issue Innovation in Efficient and Sustainable Blast Furnace Ironmaking)

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12 pages, 7669 KiB

Open AccessArticle

Precipitation Dynamics and Mechanical Properties Analysis of a Nickel-Based Superalloy Cooled Under Different Rates

by Jinhe Shi, Liwei Xie, Shengyu Liu, Baojin Chen, Lei Zhao and Kailun Zheng

Metals 2025, 15(7), 781; https://doi.org/10.3390/met15070781 - 10 Jul 2025

Viewed by 192

Abstract

The solid solution cooling heat treatment of powder, high-temperature alloys is a crucial part of the process for ensuring the strength of materials during the forging processing. The influence of the γ′ phase and other microstructures in high-temperature alloy forgings on their macroscopic [...] Read more.

The solid solution cooling heat treatment of powder, high-temperature alloys is a crucial part of the process for ensuring the strength of materials during the forging processing. The influence of the γ′ phase and other microstructures in high-temperature alloy forgings on their macroscopic mechanical properties has been confirmed in numerous studies. Among them, the performance of the γ′ phase during the solid solution cooling process varies significantly depending on the cooling rate. This study uses the FGH99 nickel-based high-temperature alloy as the research material. It examines the precipitation and microstructure evolution law of the material under different cooling rates and its impact on the macroscopic mechanical properties of the material. Additionally, a prediction model of the organizational properties based on the cooling rate is constructed. The research findings indicate that there is a distinct positive correlation between the yield strength of the material and the cooling rate. As the cooling rate increases, the yield strength rises from 910.8 MPa to 1025.4 MPa, showing an increase of 12.6%. Moreover, an increase in the cooling rate has an evident promoting effect on the refinement of the precipitation phase. When the cooling rate is elevated from 50 °C/min to 250 °C/min, the average size of the γ′ phase decreases from 106 nm to 82.1 nm, and its morphology transforms from an irregular state to a spherical shape. For the microstructure of the material, such as the size of the precipitated phase and dislocation density, the maximum prediction error of the heat treatment organization performance prediction model established in this study is 2.97%. Moreover, the prediction error of the yield strength is 1.76%. Full article

(This article belongs to the Special Issue Research on Microstructure and Performance Mechanisms of Advanced Steels and Alloys)

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23 pages, 8526 KiB

Open AccessArticle

Comparison of Fatigue Property Estimation Methods with Physical Test Data

by Sebastian Raczek, Adam Niesłony, Krzysztof Kluger and Tomasz Łukasik

Metals 2025, 15(7), 780; https://doi.org/10.3390/met15070780 - 9 Jul 2025

Viewed by 154

Abstract

Cost reduction has always been a high priority target in modern management. Concentrating on material strength, the huge potential is recognized for cost reduction in finding the material fatigue coefficients by reduction the number and time required for testing specimens. The aim of [...] Read more.

Cost reduction has always been a high priority target in modern management. Concentrating on material strength, the huge potential is recognized for cost reduction in finding the material fatigue coefficients by reduction the number and time required for testing specimens. The aim of this study is to evaluate the accuracy of several fatigue parameter estimation methods by comparing them with reference test data obtained for six different steel materials. In the literature, several estimation methods can be found. Those methods rely on tension or hardness tests. The concern is about the accuracy of those methods; therefore, a basic case was investigated involving estimation methods and comparing them to reference data from a physical test. The case was selected in a manner that allowed the verification of combined low and high cycle fatigue. As a result, the estimation methods produced a very wide range of fatigue life predictions, but some of them were quite accurate. This leads to the conclusion that estimation methods can be a step forward for finding the fatigue material properties; however, a study should be undertaken on which methods are the most suitable for the material family used. Full article

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

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16 pages, 21960 KiB

Open AccessArticle

Interplay of C Alloying, Temperature, and Microstructure in Governing Mechanical Behavior and Deformation Mechanisms of High-Manganese Steels

by Chenghao Zhang, Jinfu Zhao, Tengxiang Zhao, Ling Kong, Chunlei Zheng, Haokun Yang and Yuhui Wang

Metals 2025, 15(7), 779; https://doi.org/10.3390/met15070779 - 9 Jul 2025

Viewed by 141

Abstract

This study investigates the mechanical behavior and deformation mechanisms of Fe-30Mn-0.05C (30Mn0.05C) and Fe-34Mn-0.7C (34Mn0.7C) steels at room temperature (RT) and liquid nitrogen temperature (LNT). The 30Mn0.05C sample exhibited a significant enhancement in both strength and ductility at LNT, achieving a total elongation [...] Read more.

This study investigates the mechanical behavior and deformation mechanisms of Fe-30Mn-0.05C (30Mn0.05C) and Fe-34Mn-0.7C (34Mn0.7C) steels at room temperature (RT) and liquid nitrogen temperature (LNT). The 30Mn0.05C sample exhibited a significant enhancement in both strength and ductility at LNT, achieving a total elongation of 85%. In contrast, the 34Mn0.7C sample demonstrated superior ductility (90%) at RT, with a marginal reduction in plasticity but a remarkable increase in strength (>1100 MPa) at LNT. Compared to the 30Mn0.05C, the 34Mn0.7C, characterized by higher carbon content, displayed more pronounced dynamic strain aging (DSA) effects. Additionally, a greater density of deformation twins was activated at LNT, revealing a strong correlation between deformation twinning and DSA effects. This interplay accounts for the simultaneous strength improvement and ductility reduction observed in the 34Mn0.7C at LNT. Furthermore, the 34Mn0.7C sample exhibited a significantly refined grain structure after rolling, contributing to a substantial strength increase (approaching 1500 MPa) at the expense of ductility. This trade-off can be attributed to the pre-introduction of a higher density of dislocations and deformation twins during rolling, which facilitated strengthening but limited further plastic deformation. Full article

(This article belongs to the Special Issue Fatigue and Wear of Steel Materials: Characterization and Performance Analysis)

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13 pages, 2500 KiB

Open AccessArticle

Highly Selective Recovery of Pt(IV) from HCl Solutions by Precipitation Using 1,4-Bis(aminomethyl)cyclohexane as a Precipitating Agent

by Kazuya Matsumoto, Ryu Sakamoto, Yoshiya Sakuta, Ryota Aoki, Hiroshi Katagiri and Mitsutoshi Jikei

Metals 2025, 15(7), 778; https://doi.org/10.3390/met15070778 - 9 Jul 2025

Viewed by 159

Abstract

To ensure the sustainable use of limited resources, it is essential to establish selective and efficient recycling technologies for platinum group metals (PGMs). This study focused on the selective precipitation-based separation of Pt(IV) from hydrochloric acid (HCl) solutions in the presence of various [...] Read more.

To ensure the sustainable use of limited resources, it is essential to establish selective and efficient recycling technologies for platinum group metals (PGMs). This study focused on the selective precipitation-based separation of Pt(IV) from hydrochloric acid (HCl) solutions in the presence of various metal ions, using trans-1,4-bis(aminomethyl)cyclohexane (BACT) as a precipitating agent. By using BACT, we succeeded in the selective separation of Pt(IV) by precipitation from HCl solutions containing Pd(II) and Rh(III). Notably, selective and efficient recovery of Pt(IV) was accomplished across various HCl concentrations, with a small amount of BACT and within a short shaking time. To evaluate the practical applicability of the method, Pt(IV) was recovered and purified from the HCl leachate of spent automotive exhaust gas purification catalysts using BACT. As a result, a high Pt recovery of 95.6% and a high purity of 99.3% were achieved. Although Pt(IV) was recovered as a precipitate containing BACT, it was found that Pt black could be readily obtained by dissolving the precipitate in HCl solution followed by reduction with sodium borohydride. Detailed structural analysis of the Pt(IV)-containing precipitate revealed that it is an ionic crystal composed of [PtCl₆]²⁻ and protonated BACT. The selective formation of this ionic crystal in HCl solution, along with its stability under such conditions, is the key to the selective recovery of Pt(IV) using BACT. Full article

(This article belongs to the Special Issue Hydrometallurgical Processes for the Recovery of Critical Metals)

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22 pages, 5625 KiB

Open AccessArticle

Corrosion Resistance Mechanism in WC/FeCrNi Composites: Decoupling the Role of Spherical Versus Angular WC Morphologies

by Xiaoyi Zeng, Renquan Wang, Xin Tian and Ying Liu

Metals 2025, 15(7), 777; https://doi.org/10.3390/met15070777 - 9 Jul 2025

Viewed by 189

Abstract

In this study, we investigated the electrochemical corrosion behavior and mechanisms of FeCrNi/WC alloys with varying contents of CTC-S (spherical WC) and CTC-A (angular WC) in a 3.5 wt.% NaCl solution, addressing the corrosion resistance requirements for stainless steel composites in marine environments. [...] Read more.

In this study, we investigated the electrochemical corrosion behavior and mechanisms of FeCrNi/WC alloys with varying contents of CTC-S (spherical WC) and CTC-A (angular WC) in a 3.5 wt.% NaCl solution, addressing the corrosion resistance requirements for stainless steel composites in marine environments. The electrochemical test results demonstrate that the corrosion resistance of the alloy initially increases with the CTC-A content, followed by a decrease, which is associated with the formation, stability, and rupture of the passivated film. Nyquist and Bode diagrams for electrochemical impedance spectroscopy confirm that the charge transfer resistance of the passivated film is the primary determinant of the composite’s corrosion performance. A modest increase in CTC-A contributes to the formation of a more heterogeneous second phase, providing a physical barrier and enhancing solid solution strengthening, and thus delaying the cracking and corrosion processes of the passivation film. However, excessive CTC-A content leads to significant dissolution of the alloy’s reinforcement phase and promotes decarburization, resulting in the formation of corrosion pits, craters, and cracks that compromise the passivation film and expose fresh alloy surfaces to further corrosion. When the CTC-A content is 10% and the CTC-S content is 30%, this combination results in minimal degradation in the corrosion performance (0.213 μA·cm²) while balancing the hardness and toughness of the alloy. Additionally, electrochemical evaluations reveal that incorporating angular CTC-A particles at 10 vol% effectively delays the breakdown of the passivation film by mitigating the interfacial galvanic coupling through enhancing the mechanical interlocking at the WC/FeCrNi interface. The CTC-A/CTC-S hybrid system exhibits a remarkable 62% reduction in the pitting propagation rate compared to composites reinforced solely with spherical WC, which is attributed to the preferential dissolution of angular WC protrusions that sacrificially suppress crack initiation at the phase boundaries. Full article

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16 pages, 4888 KiB

Open AccessFeature PaperArticle

Hot Tensile Behavior of 05Cr17Ni4Cu4Nb Stainless Steel: Damage Model and Fracture Characteristics

by Jing Yuan, Hongjun Jiang, Liwei Zheng and Kuangyu Zhang

Metals 2025, 15(7), 776; https://doi.org/10.3390/met15070776 - 9 Jul 2025

Viewed by 158

Abstract

This study investigates the hot tensile behavior and fracture characteristics of 05Cr17Ni4Cu4Nb stainless steel through isothermal tensile tests conducted under various deformation parameters. An improved Cockroft & Latham (C&L) damage model, incorporating the effects of temperature and strain rate, was developed to quantitatively [...] Read more.

This study investigates the hot tensile behavior and fracture characteristics of 05Cr17Ni4Cu4Nb stainless steel through isothermal tensile tests conducted under various deformation parameters. An improved Cockroft & Latham (C&L) damage model, incorporating the effects of temperature and strain rate, was developed to quantitatively evaluate the influence of these parameters on the high-temperature deformation behavior of 05Cr17Ni4Cu4Nb stainless steel. Microstructural analysis revealed the features of ductile fracture and provided insights into the mechanism by which δ-ferrite influences microvoid evolution. These findings contribute to a deeper understanding of the high-temperature deformation behavior of 05Cr17Ni4Cu4Nb stainless steel and provide practical guidance for optimizing hot forming parameters in industrial applications. Full article

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25 pages, 3674 KiB

Open AccessArticle

CFD Modelling of Refining Behaviour in EAF: Influence of Burner Arrangement and Oxygen Flow Rates

by Sathvika Kottapalli, Orlando Ugarte, Bikram Konar, Tyamo Okosun and Chenn Q. Zhou

Metals 2025, 15(7), 775; https://doi.org/10.3390/met15070775 - 9 Jul 2025

Viewed by 169

Abstract

The electric arc furnace (EAF) process includes key stages: charging scrap metal, melting using electric arcs, refining through oxygen injection and slag formation, and tapping molten steel. Recently, EAF steelmaking has become increasingly important due to its flexibility with recycled materials, lower environmental [...] Read more.

The electric arc furnace (EAF) process includes key stages: charging scrap metal, melting using electric arcs, refining through oxygen injection and slag formation, and tapping molten steel. Recently, EAF steelmaking has become increasingly important due to its flexibility with recycled materials, lower environmental impact, and reduced investment costs. This study focuses specifically on select aspects of the refining stage, analysing decarburization and the associated exothermic oxidation reactions following the removal of carbon with oxygen injection. Particular attention is given to FeO generation during refining, as it strongly affects slag chemistry, yield losses, and overall efficiency. Using a Computational Fluid Dynamics (CFD)-based refining simulator validated with industrial data from EVRAZ North America (showing an 8.57% deviation), this study investigated the impact of oxygen injection rate and burner configuration. The results in a three-burner EAF operation showed that increasing oxygen injection by 10% improved carbon removal by 5%, but with an associated increase of FeO generation of 22%. Conversely, reducing oxygen injection by 15% raised the residual carbon content by 43% but lowered FeO by 23%. Moreover, the impact of the number of burners was analysed by simulating a second scenario with 6 burners. The results show that by increasing the number of burners from three to six, the target carbon is reached 33% faster while increasing FeO by 42.5%. Moreover, by reducing the oxygen injection in the six-burner case, it is possible to reduce FeO generation from 42.5 to 28.5% without significantly impacting carbon removal. This set of results provides guidance for burner optimization and understanding the impact of oxygen injection on refining efficiency. Full article

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