Metals

22 pages, 4323 KB

Open AccessArticle

Effect of Tempering on Microstructure, Strength and Toughness Gradient in Quenched Low-Alloy Medium-Thickness Steel Plate

by Boyu Guan, Shaobin Bai, Yongqing Zhang, Peimao Fu, Haitao Lu, Hejia Zhu, Xingchi Chen, Kaikai Guo, Haonan Wang and Yongan Chen

Metals 2026, 16(3), 243; https://doi.org/10.3390/met16030243 - 24 Feb 2026

Abstract

To elucidate how tempering temperature influences through-thickness microstructure and strength–toughness gradients in an online direct-quenched (DQ) low-alloy medium-thick plate, a 25-mm plate was direct-quenched from 900 °C to <150 °C and tempered at 530 °C × 1.5 h or 580 °C × 1.5 [...] Read more.

To elucidate how tempering temperature influences through-thickness microstructure and strength–toughness gradients in an online direct-quenched (DQ) low-alloy medium-thick plate, a 25-mm plate was direct-quenched from 900 °C to <150 °C and tempered at 530 °C × 1.5 h or 580 °C × 1.5 h. Tensile and room-temperature Charpy V-notch impact testing and microstructure characterization were performed at the upper surface, mid-thickness, and lower surface. In the as-DQ state, the upper surface contained ferrite (F, ~60%) and granular bainite (GB, ~30%) with minor lath bainite (LB, ~10%) and a small amount of martensite/austenite (M/A). The mid-thickness and lower surface remained dominated by F + GB (mid-thickness: GB~50%, F~30%, M/A~20%; lower surface: F~85%, GB~15%); the mid-thickness showed the lowest yield strength/ultimate tensile strength (YS/UTS) of 498/675 MPa. In the as-DQ state, the room-temperature Charpy V-notch absorbed energies at the upper surface, mid-thickness, and lower surface were 223.23, 229.88, and 261.22 J, respectively, indicating a pronounced through-thickness variation (ΔE_(max–min) ≈ 38 J). After tempering at 530 °C, the upper surface and mid-thickness developed an F + tempered sorbite (TS) microstructure (upper surface: F~70%, TS~30%; mid-thickness: F~60%, TS~40%), whereas the lower surface was mainly ferrite with a small amount of spheroidized carbides/tempered cementite (SC). The mid-thickness YS/UTS increased to 619/805 MPa, and the impact energies at the upper surface and mid-thickness increased to 240.62 J and 235.56 J, respectively, resulting in a reduced through-thickness gradient. After 580 °C tempering, recovery and polygonal ferrite formation dominated; surface yield strength increased but mid-thickness yield improvement was limited. Full article

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

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19 pages, 7242 KB

Open AccessArticle

Artificial Neural Network-Based Optimisation of Geometric Characteristics in Laser Metal Deposition of TiC/Ti6Al4V

by Thabo Tlale, Peter Mashinini and Bathusile Masina

Metals 2026, 16(3), 242; https://doi.org/10.3390/met16030242 - 24 Feb 2026

Abstract

Laser metal deposition operates on the principle of layer-by-layer material addition, wherein each layer is formed by overlapping individual single tracks. Consequently, clads formed serve as the fundamental building blocks for this technology. Their quality directly affects the overall build quality, particularly the [...] Read more.

Laser metal deposition operates on the principle of layer-by-layer material addition, wherein each layer is formed by overlapping individual single tracks. Consequently, clads formed serve as the fundamental building blocks for this technology. Their quality directly affects the overall build quality, particularly the geometric characteristics, which are also critical to process productivity. In the present work, geometric characteristics of TiC/Ti6Al4V single tracks fabricated via laser metal deposition are optimised. An artificial neural network model was developed to predict the clad width, height, and dilution using processing parameters, laser power, scan speed, and powder feed rate, as model inputs. The Particle Swarm Optimisation algorithm was employed for hyperparameter selection. The hyperparameter-optimised model achieved a mean squared error of 0.00183 and an R² score of 0.979 during training, and a mean squared error of 0.00709 and an R² score of 0.887 during testing. Although the small discrepancy between training and testing metrics suggests slight overfitting, likely due to the size of the dataset, the model achieved a mean absolute percentage error of less than 10% during testing. Subsequently, process plots generated by the model predictions were used to identify suitable parameters, and a processing map was developed to highlight the window that achieves suitable dilution (14–24%), defect-free sound bonding, and thick and dense clads. Full article

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

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14 pages, 2803 KB

Open AccessArticle

Influence of Low Zn Concentrations on Behavior of Historical Organ Pipes and Its Model Analogs

by Alena Michalcová, Šárka Msallamová, Elizaveta Gavel, Dominika Fink and Petra Jánošíková

Metals 2026, 16(2), 241; https://doi.org/10.3390/met16020241 - 23 Feb 2026

Abstract

This study focused on investigating the influence of zinc on tin pest, both alone and in combination with lead and copper. Based on the known composition of the organ pipe from Trpín, five model alloys were prepared, from which model samples were produced. [...] Read more.

This study focused on investigating the influence of zinc on tin pest, both alone and in combination with lead and copper. Based on the known composition of the organ pipe from Trpín, five model alloys were prepared, from which model samples were produced. The model alloys were exposed to low temperatures for 100 days or until complete degradation occurred. The kinetics of the transformation were compared for annealed and non-annealed samples. It was confirmed that the transformation is much faster in samples with retained internal stress. A comparison of the Avrami coefficients indicated similar nucleation behavior for both sample types. Phase transformation was observed in samples containing tin, copper, zinc, and lead, as well as those containing only copper and lead. This suggests that even a relatively small amount of zinc (0.25 wt.%) and copper (0.9 wt.%) can affect the course of tin pest in an alloy containing 13 wt.% lead. Transformation progressed more slowly in samples with only 0.25 wt.% zinc than in pure tin, likely due to the limited solubility of zinc in a tin with low concentrations of alloying elements. The crystallographic structure of both the model alloys and the original historical pipe material was studied using transmission electron microscopy (TEM). In almost all model samples, zinc was uniformly dissolved in the tin matrix. However, in the original pipe, zinc was primarily located at grain boundaries and in association with copper. This indicates that zinc was not intentionally added to the historical alloy but likely appeared in the alloy as a contaminant of impure copper. Full article

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24 pages, 3839 KB

Open AccessArticle

Thermodynamic and Pilot-Scale Experimental Analysis of Medium-Carbon Ferromanganese Production

by Assylbek Abdirashit, Bakyt Suleimen, Bagdagul Uakhitova, Rustem Uakhitov, Meruert Taizhigitova and Amanbek Nurtayev

Metals 2026, 16(2), 240; https://doi.org/10.3390/met16020240 - 22 Feb 2026

Abstract

This study investigates the thermodynamic and technological aspects of smelting medium-carbon ferromanganese from Zhezdinsky manganese ore using ferrosilicomanganese and lime. The equilibrium distribution of components in the oxide-metal system was calculated using HSC Chemistry 10.0 within the temperature range of 573–2073 K. The [...] Read more.

This study investigates the thermodynamic and technological aspects of smelting medium-carbon ferromanganese from Zhezdinsky manganese ore using ferrosilicomanganese and lime. The equilibrium distribution of components in the oxide-metal system was calculated using HSC Chemistry 10.0 within the temperature range of 573–2073 K. The modeling results revealed the effect of lime and ore consumption on slag phase composition as well as on manganese and silicon contents in the metallic phase. Experimental validation was performed in a laboratory Tamman resistance furnace and in a 100 kVA large-scale laboratory electric arc furnace. The chemical compositions of metal and slag were determined by bulk chemical analysis, while microstructure and local elemental distribution were examined using SEM-EDS. An increase in slag basicity was found to promote the transfer of silicon into the silicate phase while simultaneously reducing manganese losses to the slag. The large-scale laboratory smelting experiments, with a duration of 100–120 min per heat, enabled the establishment of a stable processing regime and the production of a metal with an average composition of 88.1 wt.% Mn, 1.6 wt.% C, and 0.03 wt.% Si. The corresponding slag contained approximately 15 wt.% MnO and 21 wt.% SiO₂. SEM-EDS analysis showed that the alloy possesses a heterogeneous microstructure consisting of an Fe-Mn metallic matrix with finely dispersed silicide microphases. Local silicon concentrations in these phases reach 15–24 wt.%, which explains the discrepancy between local and bulk chemical compositions. The experimental data are in good quantitative agreement with the thermodynamic modeling results, confirming that slag basicity and composition control are key factors for improving manganese recovery and stabilizing metal composition. The identified relationships can be applied in the development of industrially oriented smelting regimes for producing medium-carbon ferromanganese from Kazakhstan manganese raw materials. Full article

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26 pages, 10124 KB

Open AccessArticle

Capacitor Electrical Discharge Sintering of Amorphous Fe-Si-B Powder

by Rosa María Aranda, Petr Urban, Jesús Cintas, Juan Manuel Montes and Francisco G. Cuevas

Metals 2026, 16(2), 239; https://doi.org/10.3390/met16020239 - 21 Feb 2026

Abstract

High purity powders of Fe, Si and B mixed with atomic composition Fe₇₈Si₉B₁₃ are subjected, after arc melting, to a melt spinning process. The amorphous ribbons are transformed into powder by mechanical milling, reaching mean sizes of 65 [...] Read more.

High purity powders of Fe, Si and B mixed with atomic composition Fe₇₈Si₉B₁₃ are subjected, after arc melting, to a melt spinning process. The amorphous ribbons are transformed into powder by mechanical milling, reaching mean sizes of 65 and 262 µm, taking care of maintaining the amorphous character. The powders are sintered by means of a very quick capacitor electrical discharge (CEDS), while trying to maintain the initial structure of the powders. The CEDS process is analyzed depending on the thermal energy applied during the discharge, as well as on the particle size of the powders and the powders’ mass. The porosity, microstructure, hardness, electrical resistivity and magnetic properties of the prepared compacts are analyzed. Thus, for powders with a mean size of 262 μm, the porosity can be reduced from 0.33 to 0.11 after sintering, reaching a microhardness of up to 1100 HV₁ after applying a discharge of 2640 J/s. A coercivity of 1895 A/m and a saturation flux density of 1.32 T are achieved in the compact, which maintains a microstructure with up to 64% of amorphous phase. Full article

(This article belongs to the Special Issue Powder Metallurgy of Metals and Composites)

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17 pages, 5726 KB

Open AccessArticle

Production and Characterization of Al Alloys Obtained Through Molten Metal Deposition

by Cinzia Menapace, Jonas Galle, Chola Elangeswaran and Advenit Makaya

Metals 2026, 16(2), 238; https://doi.org/10.3390/met16020238 - 20 Feb 2026

Abstract

Two aluminum alloys (4043 and 6061) were fabricated using the innovative Molten Metal Deposition (MMD) technique. Three types of samples were produced by varying selected deposition parameters. The quality of the resulting components was assessed in terms of defects, density, and microstructure. In [...] Read more.

Two aluminum alloys (4043 and 6061) were fabricated using the innovative Molten Metal Deposition (MMD) technique. Three types of samples were produced by varying selected deposition parameters. The quality of the resulting components was assessed in terms of defects, density, and microstructure. In the 4043 alloy, the microstructure consists of α-Al dendrites surrounded by an Al–Si eutectic phase. All 4043 samples exhibited this microstructure, regardless of the deposition parameters. The mechanical response was preliminarily evaluated through HV0.5 microhardness measurements. The indentations produced under a 500 g load enabled the assessment of the contribution of both the α-Al matrix and the surrounding Al–Si eutectic. As for the 6061 alloy, its microstructure is composed of an α-Al matrix containing dispersed Al–Si–Fe intermetallics. Some oxide particles were observed at the grain boundaries, indicating the need for processing under a controlled atmosphere. In this study, no inert shielding atmosphere was used for the fabrication of the samples. Thanks to its high processing speed, sustainability, and ease of deployment, MMD can be regarded as a viable alternative to more conventional additive manufacturing technologies. Full article

(This article belongs to the Special Issue Processing, Properties, Applications and Recycling of Light Alloys)

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14 pages, 2944 KB

Open AccessArticle

Nano-Pigment Cr₂O₃ Preparation from Chromium Slag by Alkaline Roasting, Water Leaching, Glucose Reduction and Vacuum Calcination

by Huiwen Li, Zhe Gao, Shaoxiong Li, Haocheng Qin, Qianfang Yan, Zhaowang Dong, Xiangfeng Kong, Bin Yang and Hongwei Yang

Metals 2026, 16(2), 237; https://doi.org/10.3390/met16020237 - 20 Feb 2026

Abstract

Metallurgical chromium slag is a hazardous by-product generated during the production of chromium salts and metallic chromium, containing significant amounts of leachable Cr(VI), which poses severe environmental and human health risks. To address this challenge, this study presents an integrated “alkaline roasting, water [...] Read more.

Metallurgical chromium slag is a hazardous by-product generated during the production of chromium salts and metallic chromium, containing significant amounts of leachable Cr(VI), which poses severe environmental and human health risks. To address this challenge, this study presents an integrated “alkaline roasting, water leaching with impurity removal, glucose reduction and vacuum calcination” process for its direct preparation to nano-pigment-grade Cr₂O₃. The reduction process was systematically optimized by investigating the effects of critical parameters: glucose dosage, HCl concentration, reduction temperature and time. Optimal conditions were established as 2.5 g of C₆H₁₂O₆, 20 mL of 12 M HCl, 55 °C and 4 h, achieving the Cr(VI) reduction efficiency of 99.66%. Comprehensive characterization of the final product via XRD, SEM-EDS and XRF confirmed its high quality. The Cr₂O₃ exhibited a purity of 99.31%, well-developed crystallinity and a uniform sub-micron particle size distribution, fully meeting industrial standards for pigment applications. By substituting conventional hazardous reductants with glucose, this route demonstrates enhanced safety, environmental compatibility and cost-effectiveness. The proposed methodology not only provides a practical and scalable solution for the valorization of hazardous chromium slag but also contributes to the advancement of green processing technologies in the metallurgical sector, supporting the transition towards a circular economy. Full article

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18 pages, 2962 KB

Open AccessArticle

Enhancing the Selective Reduction of Nickel to Prepare FeNi50 Alloy from Saprolite-Type Laterite by CO-CO₂ Gas Pretreatment

by Zhichao Hu, Zhengliang Xue, Guihua Hang, Guo Lin, Wei Wang, Fang Huang and Yaqi Wang

Metals 2026, 16(2), 236; https://doi.org/10.3390/met16020236 - 19 Feb 2026

Abstract

Owing to the superior reduction kinetics of limonite and goethite relative to silicates, coupled with the poor beneficiation performance of saprolite-type laterite, the direct carbothermal reduction of saprolite-type laterite exhibits limited nickel selectivity. This study leverages the selective oxidation effect of CO-CO₂ [...] Read more.

Owing to the superior reduction kinetics of limonite and goethite relative to silicates, coupled with the poor beneficiation performance of saprolite-type laterite, the direct carbothermal reduction of saprolite-type laterite exhibits limited nickel selectivity. This study leverages the selective oxidation effect of CO-CO₂ atmosphere on the metallic iron of pre-reduced minerals, as well as its suppression of Fe²⁺ reduction, to promote iron migration from oxides to the silicate phase, achieving homogenization and thereby negating its kinetic advantage in reduction. Parameter optimization experiments revealed that treating pre-reduced minerals with a 30 vol% CO atmosphere at 1200 °C for 20 min achieves complete iron homogenization within the silicate phase. Compared with the nickel–iron alloy (containing less than 10 wt% Ni) obtained via the RKEF process, the combination of pre-reduction, CO-CO₂ treatment, and the melting reduction process yielded nickel–iron alloys with nickel contents of 52.1 wt% (FeNi50 alloy) and 64.2 wt% at carbon consumptions of 4.0 wt% and 3.83 wt%, respectively, accompanied by nickel recovery rates of 95.5% and 91.2%. Furthermore, the enrichment of Fe²⁺ in the slag significantly reduces its melting point to approximately 1450 °C, enabling complete slag–metal separation after smelting at 1550 °C for 10 min. Full article

(This article belongs to the Section Extractive Metallurgy)

12 pages, 4631 KB

Open AccessArticle

Effect of Metallic Y and CaF₂ on Deoxidation and Inclusion Removal in an SHS-TiAl Alloy

by Kunjie Peng, Hang Guo, Guangyao Chen, Zhihe Dou, Xinmei Hou and Chonghe Li

Metals 2026, 16(2), 235; https://doi.org/10.3390/met16020235 - 19 Feb 2026

Abstract

In this study, the metallic Y, CaF₂, and sponge Ti were employed to regulate the composition and achieve the deoxidation of the SHS-TiAl alloy, respectively. The results indicate that the metallic Y could effectively reduce the oxygen concentration of the SHS-TiAl [...] Read more.

In this study, the metallic Y, CaF₂, and sponge Ti were employed to regulate the composition and achieve the deoxidation of the SHS-TiAl alloy, respectively. The results indicate that the metallic Y could effectively reduce the oxygen concentration of the SHS-TiAl alloys, which could all be controlled below 0.06 wt.%. The alloying control of SHS-TiAl could be further realized by adding sponge Ti with the achievement of a typical α + γ phase microstructure. Additionally, the CaF₂ could adsorb the Y₂O₃ products, which were formed during the deoxidation reaction. However, due to the relatively high initial oxygen content in the SHS-TiAl alloy, the generated Y₂O₃ could not be fully removed, leading to the partial inclusions remaining in the alloy matrix. Also, the residual Y would react with Al in the alloy to form YAl₂ inclusions. Full article

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17 pages, 6008 KB

Open AccessArticle

Effect of Competitive Precipitation and Texture Weakening on Mechanical Properties in a Mg-Gd-Y-Nd-Zr Alloy Processed by Integrated Multi-Directional Forging and Extrusion

by Liqun Guan, Honglei Wang, Yingchun Wan, Jian Chen, Lidan Fan and Feifei Ji

Metals 2026, 16(2), 234; https://doi.org/10.3390/met16020234 - 19 Feb 2026

Abstract

As the lightest metallic structural material, magnesium alloys face a fundamental trade-off between strength and ductility, limiting their broader application. This study investigates a processing approach to overcome this limitation by systematically comparing the effects of direct extrusion and a multi-directional forging (MDF) [...] Read more.

As the lightest metallic structural material, magnesium alloys face a fundamental trade-off between strength and ductility, limiting their broader application. This study investigates a processing approach to overcome this limitation by systematically comparing the effects of direct extrusion and a multi-directional forging (MDF) combined extrusion process on a Mg-8Gd-4Y-1Nd-0.5Zr alloy. The results demonstrate that MDF pretreatment effectively refines grains and enhances dynamic precipitation. It also significantly weakens the texture, reducing the intensity from 11.14 to 3.98 and tilting the {0001} basal planes by approximately 30° from the extrusion direction. This texture weakening is attributed to the combined effects of particle-stimulated nucleation (PSN) and the orientation diversity introduced by pre-forging, which promote orientation randomization during recrystallization. The alloy processed by the combined route exhibits an excellent strength–ductility synergy in the as-extruded state, with ultimate tensile strength, tensile yield strength, and elongation reaching 315 MPa, 228 MPa, and 13.1%, respectively. After peak aging, the strength further increases to 429 MPa and 323 MPa while maintaining a ductility of 7.3%. Schmid factor analysis confirms that the combined process facilitates the activation of non-basal slip and improves strain compatibility through multi-slip activity, providing an effective pathway for developing high-performance wrought magnesium alloys. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

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13 pages, 1987 KB

Open AccessArticle

Machine Learning-Based Prediction of Young’s Modulus in Ti-Alloys

by Seza Dinibutun, Yousef Alshammari and Leandro Bolzoni

Metals 2026, 16(2), 233; https://doi.org/10.3390/met16020233 - 19 Feb 2026

Abstract

This study explores the use of machine learning to predict the experimental Young’s modulus of titanium alloys based on their mechanical and microstructural properties. Several regression models were developed and compared, including Random Forest, XGBoost, CatBoost, Multi-Layer Perceptron, and a Stacking Regressor. Among [...] Read more.

This study explores the use of machine learning to predict the experimental Young’s modulus of titanium alloys based on their mechanical and microstructural properties. Several regression models were developed and compared, including Random Forest, XGBoost, CatBoost, Multi-Layer Perceptron, and a Stacking Regressor. Among these, Random Forest, XGBoost and CatBoost achieved the most accurate results with R² values above 0.85. To improve interpretability, SHapley Additive exPlanations were applied to examine which input features most strongly influenced the predictions. The results showed that yield strength, hardness, and the molybdenum equivalent parameter (moe) were among the most influential descriptors. While yield strength and hardness were positively associated with the predicted values, higher moe values corresponded to lower predicted Young’s modulus. This study focuses on the prediction of Young’s modulus, a comparatively less explored elastic property in Ti-alloy machine learning studies and combines systematic model comparison with SHAP-based interpretability to provide physically consistent insights into feature–property relationships. Full article

(This article belongs to the Special Issue Machine Learning Models in Metals (2nd Edition))

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18 pages, 3330 KB

Open AccessArticle

Effect of Height Difference Between Adjacent Liquid Injection Holes on Wetting Body Evolution of Ion-Absorbed Rare Earth In Situ Leaching Ore

by Qiang Huang, Chunlei Zhang, Yunzhang Rao, Guozhu Rao, Jiazheng Wan, Yangjun Xie and Qiande Lai

Metals 2026, 16(2), 232; https://doi.org/10.3390/met16020232 - 19 Feb 2026

Abstract

This study investigated wetting body migration and blind area distribution variations under different height differences (Δh) using indoor experiments and numerical simulations. Results show that the Δh of the injection hole shifts the wetting body intersection backward. Due to the increase in Δh, [...] Read more.

This study investigated wetting body migration and blind area distribution variations under different height differences (Δh) using indoor experiments and numerical simulations. Results show that the Δh of the injection hole shifts the wetting body intersection backward. Due to the increase in Δh, the vertical migration of the wetting peak at the No. 1 liquid injection hole accelerates, and the horizontal migration tends to be stable, which indicates that the Δh promotes the vertical seepage by changing the hydraulic gradient, which is beneficial to accelerate the leaching process. The migration of the wetting peak presents the characteristics of ‘fast first and then slow’, and it is easy to form a blind area in the later stage of leaching. When Δh is 0 and 3 cm, the blind area is concentrated between the two holes in the upper part of the ore heap. When Δh increases to 5 and 7 cm, the blind area expands to the top of the No. 1 hole. The simulation results show that although the increase in Δh can accelerate the recovery of water pressure in the near-end injection hole, it will increase the difference in leaching efficiency between ‘near-end’: when Δh is small, the wetting body diffuses symmetrically and the blind area is easy to eliminate; the increase in Δh leads to the asymmetric migration of the wetting body, and the remote area faces a significant risk of a blind area due to a low water pressure and low concentration. Full article

(This article belongs to the Special Issue Rare Earth Element Extraction, Recovery, Separation and Purification)

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17 pages, 5540 KB

Open AccessArticle

Investigation of the Mechanical Properties and Friction Coefficient of Cr/CrTiAl and Cr/(CrTiAl)N/CrTiAl PVD Coatings Deposited on 42CrMo4 QT Steel

by Yavor Sofronov, Boyan Dochev, Valentin Mishev, Antonio Nikolov, Krum Petrov, Rayna Dimitrova, Milko Yordanov, Milko Angelov, Georgi Todorov and Krassimir Marchev

Metals 2026, 16(2), 231; https://doi.org/10.3390/met16020231 - 17 Feb 2026

Abstract

Test specimens fabricated from 42CrMo4 steel were subjected to heat treatment comprising quenching followed by high-temperature tempering. This treatment is commonly referred to as hardening, and the result is a tempered sorbite microstructure that provides a balanced combination of strength and plasticity. In [...] Read more.

Test specimens fabricated from 42CrMo4 steel were subjected to heat treatment comprising quenching followed by high-temperature tempering. This treatment is commonly referred to as hardening, and the result is a tempered sorbite microstructure that provides a balanced combination of strength and plasticity. In order to improve the hardness and wear resistance of the contact surfaces, two types of physical vapor deposition (PVD) coatings were deposited onto the specimens: the first was a two-component architecture Cr/CrTiAl and the second was a multilayer Cr/(CrTiAl)N/CrTiAl. In both configurations, an intermediate chromium adhesion layer was initially deposited to enhance interfacial bonding with the substrate. The adhesion strength of the deposited coatings to the steel substrates was evaluated using a standardized adhesion test. The adhesion quality was classified as HF1 (the highest adhesion class in the HF1–HF6 scale, defined in EN ISO 26443), indicating excellent interfacial bonding. The hardness and modulus of elasticity of both coatings were determined through nanoindentation. According to the measured hardness values of the two coatings, 27.3 GPa (Cr/CrTiAl) and 37.5 GPa (Cr/(CrTiAl)N/CrTiAl), they can be classified as hard coatings (hardness greater than 20 GPa). Despite the difference in hardness, the two coatings have comparable elastic modulus values: Eit = 353 GPa for the two-component architecture coating and Eit = 349 GPa for the three-component architecture coating. Tribological characterization was performed using the ball-on-disc method under dry sliding conditions over a total sliding distance of 59 m, whereby the friction coefficient (µ) was recorded. Additionally, the wear rate of the applied coatings was calculated from the measured wear volumes or profiles. The two coatings have comparable friction coefficient values (Cr/CrTiAl–μ = 0.362, Cr/(CrTiAl)N/CrTiAl–μ = 0.325), but the three-component architecture coating Cr/(CrTiAl)N/CrTiAl has a lower wear rate (k = 1.64 × 10⁻⁴) compared to the two-component architecture coating Cr/CrTiAl, which has a wear rate of k = 7.6 × 10⁻⁴. The investigated coatings have hardness, modulus of elasticity and friction coefficient values competitive with those of nitride coatings (two-component architecture and three-component architecture), and their wear rate also corresponds to generally accepted values. Full article

(This article belongs to the Special Issue Recent Advances in Surface Modification of Metallic Materials)

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15 pages, 3262 KB

Open AccessArticle

Investigation on Cryogenic Tensile Deformation Behavior and Microstructure Evolution in Bimodal Non-Basal Textured AZ31 Mg Alloy Sheet

by Qiushuo Gao, Sha Zhan, Lijia Wang and Li Hu

Metals 2026, 16(2), 230; https://doi.org/10.3390/met16020230 - 17 Feb 2026

Abstract

An AZ31 magnesium (Mg) alloy sheet with a bimodal non-basal texture (BNT sample) exhibits significant potential for a lightweight component design in the aerospace field. However, its mechanical properties and microstructure characteristics during plastic deformation under service conditions when approaching cryogenic temperatures have [...] Read more.

An AZ31 magnesium (Mg) alloy sheet with a bimodal non-basal texture (BNT sample) exhibits significant potential for a lightweight component design in the aerospace field. However, its mechanical properties and microstructure characteristics during plastic deformation under service conditions when approaching cryogenic temperatures have not been thoroughly investigated. Aiming to elucidate this issue, cryogenic tensile experiments were conducted on a BNT sample and its control group (BT sample), which possesses the typical basal texture. Furthermore, relationships between the underlying deformation mechanisms and the deformation behavior of studied sheets were investigated through a synergistic approach combining a variety of characterization techniques with visco-plastic self-consistent (VPSC) simulations. The BNT sample shows 109.1% higher ductility (~0.23 fracture elongation, FE) but 40.2% lower 0.2% proof yield stress (YS) (~155 MPa) than its BT counterpart during cryogenic tensile deformation. As for the BNT sample, initial deformation is governed by a basal ⟨a⟩ slip and {10-12} extension twin (ET). The latter mainly contributes to accommodate intergranular plastic deformation, and this role cannot be captured in VPSC modeling. Subsequent activation of unusual {10-12}-{10-12} double twin (DT), instead of pyramidal <c+a> slip, enhances strain accommodation, boosting ductility. The discrepancy between simulation and experimental results also primarily stems from the lack of explicit incorporation of {10-12}-{10-12} DT. Full article

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12 pages, 1455 KB

Open AccessArticle

Effect of Process Parameters on the Forming Limit Angle of AA2024 Aluminum Alloy in Belt-Heated Incremental Sheet Forming

by Zhengyuan Gao, Zhibing Li, Zhengfang Li, Zhiguo An, Pengfei Sun, Zhong Ren, Jiang Li, Yi Zhang, Han Lin and Zhengyang Qiao

Metals 2026, 16(2), 229; https://doi.org/10.3390/met16020229 - 16 Feb 2026

Abstract

In the belt-heated incremental sheet forming process, the influence of process parameters on the forming limit angle significantly affects the forming accuracy and quality of components. Through macro and micro experiments, this study comprehensively analyzed the effect of key process parameters on the [...] Read more.

In the belt-heated incremental sheet forming process, the influence of process parameters on the forming limit angle significantly affects the forming accuracy and quality of components. Through macro and micro experiments, this study comprehensively analyzed the effect of key process parameters on the forming limit angle and identified forming temperature, tool head diameter, and step down as the primary factors that enhance the forming limit angle. Building on this, the dislocation density and grain size of the material under various forming temperatures, tool head diameters, and step-down values were investigated, clarifying the influence of these parameters on dislocation density and grain size in belt-heated incremental sheet forming. Furthermore, the dislocation density and grain size in the cross-section of the deformed region were calculated through micro-tests, revealing the variation patterns of dislocation density and grain size under different process conditions. These findings verified the macro–micro mechanism of the effect of process parameters on the forming limit angle and led to the establishment of a control method for the forming limit angle in belt-heated incremental sheet forming. Full article

(This article belongs to the Special Issue Advanced Metallic Materials and Forming Technologies)

20 pages, 4303 KB

Open AccessArticle

Experimental Investigation on the Effect of Pre-Deformation and Quenching Method on the Mechanical Properties of Aluminum Alloy 2219

by Zhibiao Wang, Kekun Xu, Yahao Chen, Liwei Xie and Zhuo Zhang

Metals 2026, 16(2), 228; https://doi.org/10.3390/met16020228 - 16 Feb 2026

Abstract

This study investigated high-speed air-atomized water-mist impingement cooling of 2219 aluminum alloy plates using a self-developed spray-quenching setup. Cooling intensity was controlled by varying the water loading fraction, and cooling curves were recorded using embedded thermocouples. Solution–aging treatments with conventional water quenching and [...] Read more.

This study investigated high-speed air-atomized water-mist impingement cooling of 2219 aluminum alloy plates using a self-developed spray-quenching setup. Cooling intensity was controlled by varying the water loading fraction, and cooling curves were recorded using embedded thermocouples. Solution–aging treatments with conventional water quenching and mist quenching were performed, and multi-pass pre-deformation routes were applied before and/or after solution treatment. Tensile properties were evaluated at room temperature. Mist impingement cooling achieved markedly higher cooling rates than air cooling, with peak values in the order of 10³ °C/s. Higher cooling intensity improved quenching efficiency and increased strength after aging. Multi-pass pre-deformation enhanced yield strength, but reduced elongation at high deformation levels, revealing a strength–ductility trade-off. These results provide guidance for optimizing quenching and pre-deformation parameters in heat treatment of 2219 aluminum alloy components. Full article

(This article belongs to the Section Metal Casting, Forming and Heat Treatment)

12 pages, 1005 KB

Open AccessArticle

Experimental Determination and Model Prediction of the Surface Tension of CaO-SiO₂-MgO-Al₂O₃-CaF₂ Slag

by Zhimin Ding, Yongchun Guo and Mengyao Li

Metals 2026, 16(2), 227; https://doi.org/10.3390/met16020227 - 16 Feb 2026

Abstract

In this study, the surface tension of molten slag was measured using the hanging ring method. Based on the ion and molecular coexistence theory (IMCT), an activity prediction model for the CaO-SiO₂-MgO-Al₂O₃-CaF₂ slag system was established, [...] Read more.

In this study, the surface tension of molten slag was measured using the hanging ring method. Based on the ion and molecular coexistence theory (IMCT), an activity prediction model for the CaO-SiO₂-MgO-Al₂O₃-CaF₂ slag system was established, and a corresponding surface tension model was subsequently derived. The investigation explores the effects of basicity R = (w(CaO)/w(SiO₂)), the mass ratio w(MgO)/w(Al₂O₃), and the Al₂O₃ mass fraction (w, mass fraction of the corresponding oxide). Results show that the surface tension increases with higher values of R, w(MgO)/w(Al₂O₃), and w(Al₂O₃) content. The proposed model exhibits high predictive accuracy and provides a reliable tool for evaluating the surface tension of multicomponent blast furnace slags. Full article

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14 pages, 7300 KB

Open AccessArticle

Grain Size Governs Mechanical Properties of Roll-Bonded C7701/Ti/C7701 (Cu–Ni–Zn Alloy) Composite Foils via a Bonding–Diffusion–Intermetallic Cascade

by Rui Chen, Zhihe Dou, Hongmei Zhang and Tingan Zhang

Metals 2026, 16(2), 226; https://doi.org/10.3390/met16020226 - 15 Feb 2026

Abstract

Grain size plays a decisive role in governing the interface evolution and mechanical properties of ultra-thin metal composite foils. This study systematically investigates this relationship in roll-bonded C7701/Ti/C7701 (Cu-Ni-Zn alloy) composite foils. By controlling the initial grain size via pre-annealing, we demonstrate that [...] Read more.

Grain size plays a decisive role in governing the interface evolution and mechanical properties of ultra-thin metal composite foils. This study systematically investigates this relationship in roll-bonded C7701/Ti/C7701 (Cu-Ni-Zn alloy) composite foils. By controlling the initial grain size via pre-annealing, we demonstrate that a moderate grain size (~7–8 μm) optimally regulates a sequential “bonding–diffusion–intermetallic compound (IMC) formation” process at the interface. This results in a continuous, thin IMC layer and the best strength–ductility synergy (e.g., UTS ~217.5 MPa, elongation ~4.15%). In contrast, excessively fine or coarse grains lead to thick, brittle IMCs or interfacial defects, respectively, degrading performance. The mechanism by which grain size influences performance is revealed through a sequential mechanism of “bonding–diffusion–intermetallic compound formation.” Full article

(This article belongs to the Special Issue Innovative Fabrication and Characterization Techniques for Metal Powder Composites)

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13 pages, 23791 KB

Open AccessArticle

Enhanced Thermal Stability of Ni@TiO₂ Core-Shell Nanoparticles

by Lucia Bajtošová, Nikoleta Štaffenová, Elena Chochoľaková, Jan Hanuš, Vladimír Šíma and Miroslav Cieslar

Metals 2026, 16(2), 225; https://doi.org/10.3390/met16020225 - 15 Feb 2026

Abstract

Ni@TiO₂ core–shell nanoparticles were synthesized by magnetron sputtering and their structure verified by HRTEM and EDS analysis. The thermal stability of these particles was investigated using in situ TEM annealing and compared with that of pure Ni nanoparticles. While pure Ni particles [...] Read more.

Ni@TiO₂ core–shell nanoparticles were synthesized by magnetron sputtering and their structure verified by HRTEM and EDS analysis. The thermal stability of these particles was investigated using in situ TEM annealing and compared with that of pure Ni nanoparticles. While pure Ni particles sinter at 450 °C and exhibit significant growth at 800 °C, Ni@TiO₂ nanoparticles remain stable up to 700 °C, with the sintering onset between 700 and 800 °C. A simple thermal-mismatch model was applied to explain the stabilizing effect of the TiO₂ shell, demonstrating that differences in thermal expansion between Ni and TiO₂ generate interface stresses sufficient to crack the shell after the amorphous–rutile transformation. The TiO₂ coating effectively delays Ni coalescence by 250 °C relative to bare Ni, highlighting its role as a protective shell against high-temperature sintering. Full article

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

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