Metals

11 pages, 1504 KiB

Open AccessArticle

Application of an Artificial Neural Network for Efficient Computation of Chemical Activities within an EAF Process Model

by Alexander Reinicke, Til-Niklas Engbrecht, Lilly Schüttensack and Thomas Echterhof

Metals 2024, 14(6), 736; https://doi.org/10.3390/met14060736 - 20 Jun 2024

Viewed by 451

Abstract

The electric arc furnace (EAF) is considered the second most important process for the production of crude steel and is usually used for the melting of scrap. With the current emphasis on defossilization, its share in global steelmaking is likely to further increase. [...] Read more.

The electric arc furnace (EAF) is considered the second most important process for the production of crude steel and is usually used for the melting of scrap. With the current emphasis on defossilization, its share in global steelmaking is likely to further increase. Due to the large production quantities, minor improvements to the EAF process can still accumulate into a significant reduction in overall energy and resource consumption. A major aspect in the efficient operation of the EAF is achieving beneficial slag properties, as the slag influences the composition of the steel and can reduce energy losses as well as the maintenance cost. In order to investigate the EAF operation, a dynamic process model is applied. Within the model, the chemical reactions of the metal–slag system are calculated based on the activities of the involved species. In this regard, multiple models for the calculation of the chemical activities have been implemented. However, depending on the chosen model, the computation of the slag activities can be computationally demanding. For this reason, the application of a neural network for the calculation of the chemical activities within the slag is investigated. The performance of the neural network is then compared to the results of the previously applied models by using the commercial software FactSage as a reference. The validation shows that the surrogate model achieves great accuracy while keeping the computation demand low. Full article

(This article belongs to the Special Issue Electric Arc Furnace and Converter Steelmaking)

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28 pages, 20125 KiB

Open AccessArticle

Multi Response Modelling and Optimisation of Copper Content and Heat Treatment Parameters of ADI Alloys by Combined Regression Grey-Fuzzy Approach

by Nikša Čatipović, Ivan Peko, Karla Grgić and Karla Periša

Metals 2024, 14(6), 735; https://doi.org/10.3390/met14060735 - 20 Jun 2024

Viewed by 286

Abstract

This paper deals with the austempering of ductile iron (ADI) and clarifies the influential austempering parameters during the production of ADI. During the austempering process, the heat treatment parameters can be varied, thus influencing the final microstructure and, of course, the mechanical properties [...] Read more.

This paper deals with the austempering of ductile iron (ADI) and clarifies the influential austempering parameters during the production of ADI. During the austempering process, the heat treatment parameters can be varied, thus influencing the final microstructure and, of course, the mechanical properties of ADI. To appropriately conduct experiments and obtain good results, an experimental plan was developed using the Design Expert 13 software. Along with the heat treatment parameters, the influence of the copper content on the ADI toughness, tensile strength, and elongation was determined. The obtained results from this experiment were used to develop unique mathematical models which describe the influences of heat treatment and copper content on the observed mechanical properties of ADI samples. These mathematical models can be applied to predict the analysed mechanical properties of ADI in the dependence of heat treatment parameters and copper content in base ductile iron. For the multi response optimisation of toughness, tensile strength, and elongation, a hybrid grey-fuzzy technique was presented as a significant contribution to the enhancement of the analysed mechanical properties. Consequently, the copper content and heat treatment parameter levels that resulted in the maximal mechanical properties’ functions were defined. Full article

(This article belongs to the Special Issue Metal Rolling and Heat Treatment Processing)

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11 pages, 8131 KiB

Open AccessArticle

Production of Rare-Earth-Free Iron Nitride Magnets (α″-Fe₁₆N₂)

by Tetsuji Saito, Hitoshi Yamamoto and Daisuke Nishio-Hamane

Metals 2024, 14(6), 734; https://doi.org/10.3390/met14060734 - 20 Jun 2024

Viewed by 260

Abstract

To realize rare-earth-free magnets, we studied iron nitride (α″-Fe₁₆N₂) magnets, which contain no rare-earth elements. Fe-N powder with the α″-Fe₁₆N₂ phase has a high saturation magnetization comparable to high-performance rare-earth magnets but is not stable at [...] Read more.

To realize rare-earth-free magnets, we studied iron nitride (α″-Fe₁₆N₂) magnets, which contain no rare-earth elements. Fe-N powder with the α″-Fe₁₆N₂ phase has a high saturation magnetization comparable to high-performance rare-earth magnets but is not stable at temperatures over 539 K. We consolidated Fe-N powder into bulk material at low temperatures by spark plasma sintering (SPS) and spark plasma sintering with dynamic compression (SPS-DC). Fe-N magnets were successfully obtained at low temperatures of 373–573 K. The magnets produced by the SPS-DC method had a higher density than those produced by the SPS method. The density of the magnets produced by the SPS-DC method increased as the consolidation temperature increased. That produced at 373 K had a saturation magnetization of 1.07 T with a coercivity of 0.20 MA/m. Full article

(This article belongs to the Special Issue Advances in Magnetic Alloys)

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19 pages, 76396 KiB

Open AccessArticle

Preparation and Characterization of Duplex PEO/UV-Curable Powder Coating on AZ91 Magnesium Alloys

by Łukasz Florczak, Katarzyna Pojnar, Barbara Kościelniak and Barbara Pilch-Pitera

Metals 2024, 14(6), 733; https://doi.org/10.3390/met14060733 - 20 Jun 2024

Viewed by 410

Abstract

Magnesium alloys, because of their excellent strength-to-weight ratio, are increasingly used in many industries. When used in external elements, the key factor is to provide adequate anticorrosion protection. High-temperature, cured-powder coatings are widely used to protect most metals, but their use on magnesium [...] Read more.

Magnesium alloys, because of their excellent strength-to-weight ratio, are increasingly used in many industries. When used in external elements, the key factor is to provide adequate anticorrosion protection. High-temperature, cured-powder coatings are widely used to protect most metals, but their use on magnesium alloys is difficult as a result of the instability of the magnesium substrate at elevated temperatures. Another problem is ensuring the proper adhesion of the organic coating to the magnesium substrate. This paper presents the procedure for the synthesis of a duplex coating on AZ91 magnesium alloy. The topcoat was a powder coating based on acrylic resin, the main ingredient of which was glycidyl methacrylate. Because of the presence of epoxy groups, the coating was cured using ultraviolet (UV) radiation (low-temperature technology). The conversion subcoating was produced by plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte. The synthesized coating system was tested, among others, for microscopic (SEM), adhesive (mesh of cuts), and anticorrosion (EIS). The duplex PEO/UV-curable powder coating showed very good adhesion to the metal and increased the anticorrosion properties of the magnesium substrate, compared to the powder coating produced directly on the magnesium alloy and on an alternative conversion coating (synthesized in the process of chemical zircon phosphating). Full article

(This article belongs to the Special Issue Corrosion and Protection of Lightweight Engineering Materials: Mg Alloys, Al Alloys, Ti Alloys and Other Related Metals—2nd Edition)

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17 pages, 7336 KiB

Open AccessArticle

Study on the Recognition of Metallurgical Graphs Based on Deep Learning

by Qichao Zhao, Jinwu Kang and Kai Wu

Metals 2024, 14(6), 732; https://doi.org/10.3390/met14060732 - 20 Jun 2024

Viewed by 323

Abstract

Artificial intelligence has been widely applied in image recognition and segmentation, achieving significant results. However, its application in the field of materials science is relatively limited. Metallography is an important technique for characterizing the macroscopic and microscopic structures of metals and alloys. It [...] Read more.

Artificial intelligence has been widely applied in image recognition and segmentation, achieving significant results. However, its application in the field of materials science is relatively limited. Metallography is an important technique for characterizing the macroscopic and microscopic structures of metals and alloys. It plays a crucial role in correlating material properties. Therefore, this study investigates the utilization of deep learning techniques for the recognition of metallo-graphic images. This study selected microscopic images of three typical cast irons, including ductile, gray, and white ones, and another alloy, cast aluminum alloy, from the ASM database for recognition investigation. These images were cut and enhanced for training. In addition to coarse classification of material type, fine classification of material type, composition, and the conditions of image acquisition such as microscope, magnification, and etchant was performed. The MobileNetV2 network was adopted as the model for training and prediction, and ImageNet was used as the dataset for pre-training to improve the accuracy. The metallographic images could be classified into 15 categories by the trained neural networks. The accuracy of validation and prediction for fine classification reached 94.44% and 93.87%, respectively. This indicates that neural networks have the potential to identify types of materials with details of microscope, magnification, etchants, etc., supplemental to compositions for metallographic images. Full article

(This article belongs to the Special Issue Microstructure, Mechanical Properties and Solidification Behavior of Metals and Alloys (Volume 2))

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15 pages, 44792 KiB

Open AccessArticle

Slip Statistics for a Bulk Metallic Glass Treated by Cryogenic Thermal Cycling Reflect Its Optimized Plasticity

by Jiaojiao Li, Yao Liu, Wei Zhao, Huiyun Zhang, Yajun Zhang, Huihu Lu, Zhong Wang and Yong Liu

Metals 2024, 14(6), 731; https://doi.org/10.3390/met14060731 - 20 Jun 2024

Viewed by 253

Abstract

Enhanced plasticity is obtained in a structurally rejuvenated Zr-based bulk metallic glass (BMG) that has been treated via cryogenic thermal cycling (CTC) for one hundred cycles. More than one primary shear band is activated due to the structural rejuvenation, which can inhibit the [...] Read more.

Enhanced plasticity is obtained in a structurally rejuvenated Zr-based bulk metallic glass (BMG) that has been treated via cryogenic thermal cycling (CTC) for one hundred cycles. More than one primary shear band is activated due to the structural rejuvenation, which can inhibit the jerky and system-spanning propagation of shear bands to generate sluggish shear-dynamics. These are mapped to the slip statistics, including the decreased critical avalanche size, the much longer avalanche duration of large (system-spanning) slips, and a great number of small avalanches. Moreover, the universal scaling of slip avalanches for three applied stress ranges is addressed to predict the applied stress at which the failure avalanche appears most. These results indicate that slip statistics can be the fingerprints to show how much the BMG is rejuvenated, and the failure avalanche provides a good opportunity to intervene in the failure of BMGs in advance. Full article

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14 pages, 14586 KiB

Open AccessArticle

Sustainable Recovery of Silver and Copper Photovoltaic Metals from Waste-Conductive Silver Pastes Using Thiosulfate Extraction and Ultraviolet Photolysis

by Qing Tao, Chao Han, Qiankun Jing and Guangxin Wang

Metals 2024, 14(6), 730; https://doi.org/10.3390/met14060730 - 20 Jun 2024

Viewed by 497

Abstract

Waste-conductive silver pastes are considered an important secondary resource. The recovery of metals from waste-conductive silver pastes have high economic value. The traditional cyanidation method has serious environmental pollution, while the thiosulfate method is green, environmentally friendly, and has become a viable alternative [...] Read more.

Waste-conductive silver pastes are considered an important secondary resource. The recovery of metals from waste-conductive silver pastes have high economic value. The traditional cyanidation method has serious environmental pollution, while the thiosulfate method is green, environmentally friendly, and has become a viable alternative for metal extraction. The exposure of thiosulfate complexes to ultraviolet (UV) light has been found to generate metal sulfides, and this can be used to realize the recovery of valuable metals. In this study, the extraction of silver and copper from conductive silver pastes was systematically performed using sodium thiosulfate, and the effects of sodium thiosulfate concentration, solid-to-liquid ratio, and extraction and photolytic process temperatures were investigated. The photolytic products were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. After 4 h of UV irradiation with a wavelength of 254 nm, 87% of silver and 49% of copper were recovered and transformed into silver and copper sulfide, respectively. This study demonstrates that thiosulfate can be applied in combination with UV photolysis technology to recover valuable metals in an environmentally friendly manner. Full article

(This article belongs to the Special Issue Metal Recovery and Separation from Scraps and Wastes)

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18 pages, 11313 KiB

Open AccessArticle

Investigation of Laser-MIG Hybrid Welding of Al-Mg-Si Aluminum Alloy

by Wen Zhang and Shaogang Wang

Metals 2024, 14(6), 729; https://doi.org/10.3390/met14060729 - 20 Jun 2024

Viewed by 264

Abstract

In this paper, Al-Mg-Si alloys with a thickness of 4 mm are welded by using laser beam welding (LBW) and laser-MIG hybrid welding, respectively, and the microstructure and mechanical properties of the two joints are investigated. The results show that the fusion zone [...] Read more.

In this paper, Al-Mg-Si alloys with a thickness of 4 mm are welded by using laser beam welding (LBW) and laser-MIG hybrid welding, respectively, and the microstructure and mechanical properties of the two joints are investigated. The results show that the fusion zone (FZ) of the two joints is composed of columnar crystal and equiaxed dendrite grain, and its main constituent phases are an α-Al matrix phase and a β(Mg₂Si) strengthening phase. In the case of similar heat inputs, compared with those of the LBW joint, the grain size in the laser-MIG hybrid joint is smaller and there are more second phases such as the β phase in the FZ, which is related to the different action mechanisms on the base metal (BM) by the two welding processes. Under the three strengthening mechanisms of fine grain strengthening, precipitation strengthening, and solid solution strengthening, the laser-MIG hybrid welding joint shows better mechanical properties than that of the LBW joint. The maximum tensile strength of the LBW joint and the laser-MIG hybrid joint is 202 MPa and 253 MPa, respectively, and the elongation is 3.8% and 5.1%, respectively. Full article

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17 pages, 33705 KiB

Open AccessArticle

Tunability of Martensitic Transformation with Cohesive Energies for Fe_80−xMn_xCo₁₀Cr₁₀ High-Entropy Alloys

by Yu Cao, Xiaoliang Zhang, Daoxuan Zhou, Peng Wang, Deng Pan and Hongtao Wang

Metals 2024, 14(6), 728; https://doi.org/10.3390/met14060728 - 19 Jun 2024

Viewed by 371

Abstract

Multi-element alloys (e.g., non-equiatomic FeMnCoCr alloys) have attracted extensive attention from researchers due to the breaking of the strengthen-ductility tradeoff relationship. Plenty of work has been conducted to investigate the ingredient-dependent deformation mechanism in these alloys in experiments. However, the atomic simulations on [...] Read more.

Multi-element alloys (e.g., non-equiatomic FeMnCoCr alloys) have attracted extensive attention from researchers due to the breaking of the strengthen-ductility tradeoff relationship. Plenty of work has been conducted to investigate the ingredient-dependent deformation mechanism in these alloys in experiments. However, the atomic simulations on such parameter-related mechanisms are greatly limited with the lack of the related interatomic potentials. In this work, two interatomic potentials are developed within the embedded atom method (EAM) framework for Fe_80−xMn_xCo₁₀Cr₁₀ high-entropy alloys. The tunability of the cohesive energy-related martensitic transformation (MT) mechanism was comprehensively investigated using molecular dynamics (MD) through a series of unilateral crack configurations with different twin boundary spacings (TBs). It is noted that the main deformation mechanism around the crack tip is transformed from a martensitic transformation to dislocation activities (dislocation or twin) with the variation of different cohesive energies between face-centered cubic (fcc) and hexagonal close-packed (hcp) phases. Additionally, the introduction of twin boundaries significantly enhances the strength and toughness of the alloys. The newly developed interatomic potentials are expected to provide theoretical support for the related simulations, focusing the martensitic transformation mechanism on high-entropy alloys. Full article

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

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15 pages, 11182 KiB

Open AccessArticle

Failure Analysis of the Half-Shafts Belonging to a Three-Wheeled Electric Vehicle

by Inês Mendes, J. Henrique Lopes, Eduardo Matos Almas and Luís Reis

Metals 2024, 14(6), 727; https://doi.org/10.3390/met14060727 - 19 Jun 2024

Viewed by 282

Abstract

In the electric vehicles studied, the driven wheels and the differential, which are responsible for the transfer of power and rotational motion, are connected by half-shafts. The failure of two half-shafts in the rear gearbox of a three-wheeled electric vehicle, popularly known as [...] Read more.

In the electric vehicles studied, the driven wheels and the differential, which are responsible for the transfer of power and rotational motion, are connected by half-shafts. The failure of two half-shafts in the rear gearbox of a three-wheeled electric vehicle, popularly known as a Tuk Tuk, is examined and evaluated in this research. Therefore, the primary goal of this work is to look at the factors that contribute to the failure of the aforementioned components. Visual examination and fractographic analysis were performed utilizing optical and scanning electron microscopes to investigate the half-shafts’ mode of failure. Samples from both half-shafts were obtained for tensile testing, metallographic examination, chemical composition analysis, and fracture surface analysis. According to visual examination, reversed bending fatigue, occurring simultaneously with torsion loading, caused the fracture in the half-shaft to the left of the differential (rear view). Analysis of the fracture surface of the half-shaft to the right of the differential revealed that it resulted mainly from bending fatigue loading. Moreover, regarding the mechanical design safety of the half-shafts, calculations were performed considering different trajectories, limit speeds, and different design criteria. Finally, some recommendations are drawn to improve the design safety of this mechanical component. Full article

(This article belongs to the Special Issue Failure of Metals: Fracture and Fatigue of Metallic Materials)

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13 pages, 7294 KiB

Open AccessArticle

Effect of Annealing and Double Aging on the Microstructure and Mechanical Properties of Hot-Rolled Al₁₇Cr₁₀Fe₃₆Ni₃₆Mo₁ Alloy

by Yunji Qiu, Xinbo Shi, Xiaoming Liu, Zhihua Chen, Jianbin Wang, Xin Liu, Xiaoyu Bai, Feng He and Zhijun Wang

Metals 2024, 14(6), 726; https://doi.org/10.3390/met14060726 - 19 Jun 2024

Viewed by 295

Abstract

AlCrFeNi multi-component alloys with excellent mechanical properties have been designed and extensively investigated in recent years. The massive fabrication of sheets will be an effective way for industrial application, where hot rolling is the inevitable process. After hot rolling, the mechanical properties could [...] Read more.

AlCrFeNi multi-component alloys with excellent mechanical properties have been designed and extensively investigated in recent years. The massive fabrication of sheets will be an effective way for industrial application, where hot rolling is the inevitable process. After hot rolling, the mechanical properties could be further tailored. In this study, the effects of heat treatments on a dual-phase Al₁₇Cr₁₀Fe₃₆Ni₃₆Mo₁ hot-rolled plate were systematically investigated, including: (i) annealing (700 °C, 850 °C, 1000 °C and 1150 °C for 1 h, respectively), (ii) solution and single aging (1150 °C for 1 h and 700 °C for 4 h), (iii) solution and double aging (1150 °C for 1 h, 700 °C for 4 h and 650 °C for 1 h). The B2 precipitates with varied morphologies were observed in the FCC matrix of the hot-rolled alloy after a heat treatment range from 700 °C to 1000 °C for 1 h, and the BCC particles in the B2 matrix were dissolved when the heat treatment temperature was higher than 1000 °C. The hot-rolled alloy heat treated at 700 °C for 1 h had the highest yield strength, and the hot-rolled alloy treated at 1150 °C for 1 h showed the lowest yield strength. After a solution at 1150 °C for 1 h, aging at 700 °C for 4 h and 650 °C for 1 h, the L1₂ phase and BCC particles were precipitated in the FCC and B2 matrices, and B2 nanoprecipitates were observed around the FCC grain boundaries. The solution and double aging alloy exhibit the tensile strength of 1365.7 ± 9.5 MPa, a fracture elongation of 14.2 ± 1.5% at 20 °C, a tensile strength of 641.4 ± 6.0 MPa, and a fracture elongation of 16.9 ± 1.0% at 700 °C, showing great potential for application. Full article

(This article belongs to the Special Issue Design, Processing and Characterization of Metals and Alloys)

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11 pages, 4736 KiB

Open AccessArticle

Study on Formability Improvement of Zr-4 Sheets Based on Texture Optimization

by Huan Liu, Hong-Wu Song, Si-Ying Deng, Shuai-Feng Chen and Shi-Hong Zhang

Metals 2024, 14(6), 725; https://doi.org/10.3390/met14060725 - 19 Jun 2024

Viewed by 237

Abstract

A positioning grid is a key clamping structure for fixing the transverse and axial positions of fuel assemblies in nuclear reactors, and it is generally prepared by the transverse stamping of a Zr-4 sheet. However, the texture formed in the processing process of [...] Read more.

A positioning grid is a key clamping structure for fixing the transverse and axial positions of fuel assemblies in nuclear reactors, and it is generally prepared by the transverse stamping of a Zr-4 sheet. However, the texture formed in the processing process of Zr-4 sheets can affect formability, resulting in cracking in the stamping process. Therefore, the relationship between the formability of Zr-4 sheets and the normal Kearns factor (Fn) of basal texture was studied in this paper. The results showed that the Zr-4 sheet with an Fn equaling 0.720, prepared by an isobaric reduction rolling process, would crack in the stamping process. To avoid the cracking during stamping, the formability improvement of Zr-4 sheets based on texture optimization was discussed. By using the finite element model (FEM) and a visco plastic self-consistent (VPSC) model coupled simulation, the relationship between the initial textures and formabilities of Zr-4 sheet is established. It is found that the hardening exponents (n) decreased with increasing Fns in VPSC simulations. Meanwhile, as the Fn increases, cracks are prone to occur at the bottom corner of the stamped sheet in finite element simulation. Given the results from FEM and VPSC simulations, it is proposed that the Fn should be controlled to be less than 0.7 for preventing cracks in the sheet during stamping. Additionally, a new rolling process named non-isobaric reduction rolling was designed in which the Fn of the Zr-4 sheet is successfully reduced to 0.690. The stamping results indicate that the sheet is free of cracks under an Fn of 0.690. Therefore, texture optimization with the proposed rolling process can improve the formability of Zr-4 sheets, which effectively solves the cracking problem of Zr-4 sheets. Full article

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

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11 pages, 7939 KiB

Open AccessArticle

Effect of B2 Precipitation on Hot Ductility of Fe–22Mn–9Al–0.6C Low-Density Steel

by Jun Wang, Tinghui Man, Yihao Zhou, Xicheng Wei and Han Dong

Metals 2024, 14(6), 724; https://doi.org/10.3390/met14060724 - 19 Jun 2024

Viewed by 309

Abstract

Fe–Mn–Al–C low-density steels are regarded as promising materials applied in the automotive industry to achieve the minimization of vehicular emissions and fuel consumption. This study investigates the high-temperature strength and hot ductility of Fe–22Mn–9Al–0.6C low-density steel through high-temperature tensile tests at 800–950 °C. [...] Read more.

Fe–Mn–Al–C low-density steels are regarded as promising materials applied in the automotive industry to achieve the minimization of vehicular emissions and fuel consumption. This study investigates the high-temperature strength and hot ductility of Fe–22Mn–9Al–0.6C low-density steel through high-temperature tensile tests at 800–950 °C. The high-temperature strength decreases with an increasing deformation temperature. This indicates that the precipitation of B2 reduces the hot ductility during the hot deformation of steel, where the results are consistent with those during the solid-solution treatment at 800–950 °C with a holding time of 0.5 h. Furthermore, at 800 °C the γ transforms into a mixture of α + DO₃ and κ-carbide precipitates. A transformation of κ + DO₃→B2 occurs in the temperature range of 850–900 °C, and at this point the κ-carbide dissolves into the matrix and B2 is generated, resulting in a significant decrease in hot ductility. As the temperature increases up to 950 °C, B2 emerges and transforms into the δ phase, and the κ-carbide precipitates along the γ/γ grain boundaries. The precipitation of B2 during high-temperature treatments in Fe-Mn-Al-C low-density steels is the critical factor affecting hot ductility, leading to crack generation; therefore, it is extremely essential to prevent the temperature interval of B2 precipitation during hot deformation processes. Full article

(This article belongs to the Special Issue Novel Insights and Advances in Steels and Cast Irons)

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26 pages, 18434 KiB

Open AccessArticle

Effect of Fiber-Laser Parameters on Cutting Accuracy of Thin and Thick S355JR Structural Steel Plates

by Laura Cepauskaite and Regita Bendikiene

Metals 2024, 14(6), 723; https://doi.org/10.3390/met14060723 - 18 Jun 2024

Viewed by 287

Abstract

Fiber lasers, the latest laser-cutting technology, are notable for their high process efficiency, cutting precision, and high cutting quality for thin materials. However, the quality of the cut significantly decreases when machining thicker materials. For now, this is a challenge for the metalworking [...] Read more.

Fiber lasers, the latest laser-cutting technology, are notable for their high process efficiency, cutting precision, and high cutting quality for thin materials. However, the quality of the cut significantly decreases when machining thicker materials. For now, this is a challenge for the metalworking industry. This study investigated the effects of laser power, cutting speed, and auxiliary gas pressure on the fiber-laser cutting quality of 4 and 6 mm thick S355JR steel plates. To evaluate the influence of cutting parameters on cutting quality, surface roughness, dimensional accuracy and cut taper were measured. A microscopic analysis of the laser cuts was performed, revealing the heat-affected zone, transition zone and unaffected base-material zone. Research results show that laser cutting is a complex process, and the correct choice of cutting parameters greatly influences the cutting performance and final quality. An artificial neural network was created and trained using the results from measuring the quality characteristics to achieve optimum cutting quality. The accuracy of the optimization model was assessed by control samples, which were cut using calculated optimum parameters. The actual values of the quality characteristics only slightly differ from the predicted values, showing that the optimization model is suitable for selecting cutting parameters. Full article

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11 pages, 8743 KiB

Open AccessArticle

Comparative Study of the Mechanical Properties and Fracture Mechanism of Ti-5111 Alloys with Three Typical Microstructures

by Haitao Liu, Longlong Lu, Yanmin Zhang, Fei Zhou and Kexing Song

Metals 2024, 14(6), 722; https://doi.org/10.3390/met14060722 - 18 Jun 2024

Viewed by 330

Abstract

In this work, Ti-5111 alloys with equiaxed, bimodal and lamellar microstructures were prepared by various heat treatment processes. The room-temperature tensile properties, deformation microstructure and fracture mechanism of the alloys with different microstructures were investigated. Furthermore, the mechanism by which the microstructure affects [...] Read more.

In this work, Ti-5111 alloys with equiaxed, bimodal and lamellar microstructures were prepared by various heat treatment processes. The room-temperature tensile properties, deformation microstructure and fracture mechanism of the alloys with different microstructures were investigated. Furthermore, the mechanism by which the microstructure affects the mechanical properties of Ti-5111 alloys with three typical microstructures was confirmed. The Ti-5111 alloy with a bimodal microstructure has minimum grain size and a large number of α_s/β phase boundaries, which are the primary reasons for its higher strength. Simultaneously, the excellent coordination in the deformation ability between the lamellar α_s and β phases is what enables the alloy with a bimodal microstructure to have the most outstanding mechanical properties. Additionally, the presence of a grain boundary α phase and the parallel arrangement of a coarse α_s phase are the main reasons for the inferior mechanical properties of the Ti-5111 alloy with a lamellar microstructure. The fracture mechanism of the alloy with an equiaxed microstructure is a mixed fracture mechanism including ductile fracture and destructive fracture. The fracture mechanisms of the Ti-5111 alloy with bimodal and lamellar microstructures are typical ductile fracture and cleavage fracture, respectively. These findings serve as a guide for the performance improvement and application of the Ti-5111 alloy. Full article

(This article belongs to the Special Issue Mechanical Behaviors and Damage Mechanisms of Metallic Materials)

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15 pages, 6616 KiB

Open AccessArticle

Temperature Dependency of Modified Mohr–Coulomb Criterion Parameters for Advanced High Strength Dual-Phase Steel DP780

by Yukuan Li, Di Li, Hui Song, Yiqun Wang and Dongze Wu

Metals 2024, 14(6), 721; https://doi.org/10.3390/met14060721 - 17 Jun 2024

Viewed by 313

Abstract

The Modified Mohr–Coulomb criterion has been demonstrated to exhibit high accuracy in the prediction of fracture in high-strength steels. Taking DP780 as the research object, the undetermined parameters of the Modified Mohr–Coulomb criterion at different temperatures were calibrated by tensile and shear tests [...] Read more.

The Modified Mohr–Coulomb criterion has been demonstrated to exhibit high accuracy in the prediction of fracture in high-strength steels. Taking DP780 as the research object, the undetermined parameters of the Modified Mohr–Coulomb criterion at different temperatures were calibrated by tensile and shear tests combined with simulation. The relationships between the parameters and temperature were investigated. Finally, the relationship between criterion parameters and temperature was verified using the stretch-bending tests of U-shape parts. The fracture of automotive parts can be accurately predicted by simulation during warm stamping, thereby guiding actual production. Full article

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

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14 pages, 28186 KiB

Open AccessArticle

Low-Cycle Corrosion Fatigue Deformation Mechanism for an α+β Ti-6Al-4V-0.55Fe Alloy

by Yangyang Sun, Shenwei Qian, Hui Chang, Liang Feng, Feng Li and Lian Zhou

Metals 2024, 14(6), 720; https://doi.org/10.3390/met14060720 - 17 Jun 2024

Viewed by 361

Abstract

Titanium alloys with high strength and good corrosion resistance have become one of the critical bearing structural materials in marine engineering. But in service, corrosion fatigue would occur under the synergetic action of cyclic external load and corrosion environment, threatening the safety of [...] Read more.

Titanium alloys with high strength and good corrosion resistance have become one of the critical bearing structural materials in marine engineering. But in service, corrosion fatigue would occur under the synergetic action of cyclic external load and corrosion environment, threatening the safety of components. In this study, compared with low-cycle fatigue in laboratory air, the low-cycle corrosion fatigue deformation mechanism and fracture characteristic of the Ti-6Al-4V-0.55Fe alloy were investigated in 3.5% NaCl corrosion solution under selected stress amplitudes. The results showed that under low stress amplitude, corrosion fatigue was determined by fatigue damage and corrosion damage, causing a reduction in fatigue life. The local stress concentration caused by corrosion pits and dislocations pile-up accelerated the initiation of fatigue cracks, and other corrosion behavior including crevice corrosion promoted fatigue crack propagation; the corrosion solution increased the surface damage. While under high stress amplitude, due to the short contact time between the sample and solution and higher applied stress, the fatigue life is determined by fatigue damage caused by multiple slips. Full article

(This article belongs to the Special Issue Alloy: Creep–Fatigue Interaction, Damage Mechanisms and Environmental Effects)

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18 pages, 7838 KiB

Open AccessArticle

Environmental Implications of the Soil-to-Groundwater Migration of Heavy Metals in Mining Area Hotspots

by Jelena Vesković and Antonije Onjia

Metals 2024, 14(6), 719; https://doi.org/10.3390/met14060719 - 17 Jun 2024

Viewed by 485

Abstract

Groundwater contamination was studied at several hotspot sites in the Majdanpek copper mining area (Serbia). These sites include a milling facility, a metallurgical wastewater treatment plant, a heavy vehicle service area, and a waste disposal site. In addition to Cu, high concentrations of [...] Read more.

Groundwater contamination was studied at several hotspot sites in the Majdanpek copper mining area (Serbia). These sites include a milling facility, a metallurgical wastewater treatment plant, a heavy vehicle service area, and a waste disposal site. In addition to Cu, high concentrations of As and heavy metals (Cd and Pb) were detected in groundwater and soil at the same sampling points. Mining operations and heavy vehicle transport activities have been identified as the main sources of pollution. The migration of metals from soil to groundwater, expressed as a concentration ratio, were the highest for Co and the lowest for Mn. The environmental implications of groundwater pollution were studied using the heavy metal pollution index (HPI), Nemerov pollution index (NPI), hazard index (HI), and incremental lifetime cancer risk (ILCR). HPI and NPI show the high potential of groundwater to have adverse environmental effects. HPI ranges in the following descending order of metals: Cd > Pb > As > Mn > Ni > Cr > Hg > Cu > Zn. NPI exceeds the threshold of 0.7 in 66.7% of the samples. Potential human exposure to the studied groundwater may cause severe health problems in adults, with HI ranging from 0.61 to 5.45 and ILCR from 1.72 × 10⁻⁴ to 1.27 × 10⁻³. Children were more susceptible to non-carcinogenic risk than adults, with HI ranging from 0.95 to 8.27. However, the results indicated that children were less prone to carcinogenic risks, with ILCR ranging from 5.35 × 10⁻⁵ to 3.98 × 10⁻⁴. Arsenic is the most contributing element to both risks. This research imposes the need for enhanced groundwater monitoring at hotspots in the mining area and the adoption of remediation plans and measures. Full article

(This article belongs to the Special Issue Comprehensive Utilization of Metallurgical Resources and Environmental Protection)

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15 pages, 4992 KiB

Open AccessArticle

Distribution Behavior of Impurities during the Hydrogen Reduction Ironmaking Process

by Hao Wang, Fupeng Liu, Hong Zeng, Jinfa Liao, Jinliang Wang and Chaobin Lai

Metals 2024, 14(6), 718; https://doi.org/10.3390/met14060718 - 17 Jun 2024

Viewed by 365

Abstract

The traditional blast furnace ironmaking process is the most widely used ironmaking process globally, yet it is associated with significant drawbacks, including high energy consumption and carbon emissions. To achieve low-carbon ironmaking, researchers have developed hydrogen ironmaking, which is capable of achieving lower [...] Read more.

The traditional blast furnace ironmaking process is the most widely used ironmaking process globally, yet it is associated with significant drawbacks, including high energy consumption and carbon emissions. To achieve low-carbon ironmaking, researchers have developed hydrogen ironmaking, which is capable of achieving lower CO₂ emissions. Nevertheless, the distribution behavior of impurities has been less studied in the existing research on hydrogen ironmaking. Therefore, in this study, the factors affecting the slag properties and distribution of impurity elements during hydrogen ironmaking were investigated using FactSage, and smelting experiments were carried out. The results show that temperature has the greatest influence on the distribution behavior of the impurities, and excessively elevated temperatures result in the ingress of a significant quantity of impurities into the reduced iron. Reduced iron with a purity of 98.52% was obtained under the conditions of 10%, 10%, 2%, and 2% ratios of CaO, SiO₂, MgO, and Al₂O₃, respectively, a hydrogen flow rate of 12 mL/min, and a temperature of 1400 °C; Lg L Mg, Lg L Al, Lg L Si, and Lg L Ca were 2.72, 2.41, 3.36, and 2.45, respectively (“L” stands for slag-to-metal ratio). The slag was mainly dominated by the silicate, and the iron was mainly lost in the form of mechanical inclusions in the slag. This study will enrich the basic theory of hydrogen ironmaking and is of great significance for the realization of carbon neutralization. Full article

(This article belongs to the Special Issue Low-Carbon Metallurgy Technology towards Carbon Neutrality (2nd Edition))

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21 pages, 29925 KiB

Open AccessArticle

The Impact of Multiple Thermal Cycles Using CMT^® on Microstructure Evolution in WAAM of Thin Walls Made of AlMg5

by Vinicius Lemes Jorge, Felipe Ribeiro Teixeira, Sten Wessman, Americo Scotti and Sergio Luiz Henke

Metals 2024, 14(6), 717; https://doi.org/10.3390/met14060717 - 17 Jun 2024

Viewed by 442

Abstract

Wire Arc Additive Manufacturing (WAAM) of thin walls is an adequate technology for producing functional components made with aluminium alloys. The AlMg5 family is one of the most applicable alloys for WAAM. However, WAAM differs from traditional fabrication routes by imposing multiple thermal [...] Read more.

Wire Arc Additive Manufacturing (WAAM) of thin walls is an adequate technology for producing functional components made with aluminium alloys. The AlMg5 family is one of the most applicable alloys for WAAM. However, WAAM differs from traditional fabrication routes by imposing multiple thermal cycles on the material, leading the alloy to undergo cyclic thermal treatments. Depending on the heat source used, thermal fluctuation can also impact the microstructure of the builds and, consequently, the mechanical properties. No known publications discuss the effects of these two WAAM characteristics on the built microstructure. To study the influence of multiple thermal cycles and heat source-related thermal fluctuations, a thin wall was built using CMT-WAAM on a laboratory scale. Cross-sections of the wall were metallographically analysed, at the centre of a layer that was re-treated, and a region at the transition between two layers. The focus was the solidification modes and solubilisation and precipitations of secondary phases. Samples from the wall were post-heat treated in-furnace with different soaking temperatures and cooling, to support the results. Using numerical simulations, the progressive thermal cycles acting on the HAZ of one layer were simplified by a temperature sequence with a range of peak temperatures. The results showed that different zones are formed along the layers, either as a result of the imposed thermal cycling or the solidification mode resulting from CMT-WAAM deposition. In the zones, a band composed of coarse dendrites and an interdendritic phase and another band formed by alternating sizes of cells coexisted with the fusion and heat-affected zones. The numerical simulation revealed that the thermal cycling did not significantly promote the precipitation of second-phase particles. Full article

(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Additive Manufacturing Technology)

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13 pages, 8954 KiB

Open AccessArticle

On the Enhancement of Material Formability in Hybrid Wire Arc Additive Manufacturing

by João P. M. Pragana, Beatriz Brito, Ivo M. F. Bragança, Carlos M. A. Silva and Paulo A. F. Martins

Metals 2024, 14(6), 716; https://doi.org/10.3390/met14060716 - 17 Jun 2024

Viewed by 337

Abstract

This paper is focused on improving material formability in hybrid wire-arc additive manufacturing comprising metal forming stages to produce small-to-medium batches of customized parts. The methodology involves fabricating wire arc additive manufactured AISI 316L stainless steel parts subjected to mechanical and thermal processing [...] Read more.

This paper is focused on improving material formability in hybrid wire-arc additive manufacturing comprising metal forming stages to produce small-to-medium batches of customized parts. The methodology involves fabricating wire arc additive manufactured AISI 316L stainless steel parts subjected to mechanical and thermal processing (MTP), followed by microhardness measurements, tensile testing with digital image correlation, as well as microstructure and microscopic observations. Results show that mechanical processing by pre-straining followed by thermal processing by annealing can reduce material hardness and strength, increase ductility, and eliminate anisotropy by recrystallizing the as-built dendritic-based columnar grain microstructure into an equiaxed grain microstructure. Full article

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

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16 pages, 7208 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Ti-6Al-4V In Situ Alloyed with 3 wt% Cr by Laser Powder Bed Fusion

by Valerie Sue Goettgens, Luca Weber, Jakob Braun, Lukas Kaserer, Ilse Letofsky-Papst, Stefan Mitsche, David Schimbäck and Gerhard Leichtfried

Metals 2024, 14(6), 715; https://doi.org/10.3390/met14060715 - 16 Jun 2024

Viewed by 547

Abstract

This work studied the microstructure and mechanical properties of Ti-6Al-4V in situ alloyed with 3 wt% Cr by laser powder bed fusion (LPBF). Specimens with a relative density of 99.14 ± 0.11% were produced, showing keyhole and lack of fusion pores. Due to [...] Read more.

This work studied the microstructure and mechanical properties of Ti-6Al-4V in situ alloyed with 3 wt% Cr by laser powder bed fusion (LPBF). Specimens with a relative density of 99.14 ± 0.11% were produced, showing keyhole and lack of fusion pores. Due to incomplete mixing of the components during melting, chemical inhomogeneities were observed in the solidified material. The addition of Cr promoted thermal supercooling during solidification and induced a reduction in the primary β grain size in the longitudinal direction and a weakening of the otherwise strong ⟨100⟩_β texture, both typical issues for Ti-6Al-4V produced by LPBF. The primary β at first transformed martensitically to α’, but by preheating the substrate plate to 500 °C and cyclically reheating the material by melting subsequent layers, in situ martensite decomposition was achieved, resulting in a fine lamellar α + β microstructure. In addition, the B19 phase was detected in the β matrix, presumably caused by Fe impurities in the Cr powder feedstock. Specimens exhibited a hardness of 402 ± 18 HV₁₀, and an excellent ultimate tensile strength of 1450 ± 22 MPa at an elongation at break of 4.5 ± 0.2%. Full article

(This article belongs to the Section Additive Manufacturing)

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20 pages, 9844 KiB

Open AccessArticle

Micro-WEDM of Ti-29Nb-13Ta-4.6Zr Alloy for Antibacterial Properties: Experimental Investigation and Optimization

by Shahid Ali, Salikh Omarov, Altynay Utebayeva, Tri Thanh Pham, Didier Talamona and Asma Perveen

Metals 2024, 14(6), 714; https://doi.org/10.3390/met14060714 - 16 Jun 2024

Viewed by 527

Abstract

Recent developments of orthopedic implant applications have discovered a variety of new metallic biomaterials known as β-type titanium alloys. The μ-WEDM (micro-wire electro discharge machining) surface treatment technique, capable of improving the surface properties of orthopedic implants, was studied in a machining Ti-29Nb-13Ta-4.6Zr [...] Read more.

Recent developments of orthopedic implant applications have discovered a variety of new metallic biomaterials known as β-type titanium alloys. The μ-WEDM (micro-wire electro discharge machining) surface treatment technique, capable of improving the surface properties of orthopedic implants, was studied in a machining Ti-29Nb-13Ta-4.6Zr alloy. This study aimed to evaluate material removal rate (MRR), kerf width, average surface roughness, microhardness and antibacterial response at different machining parameters which are capacitance (1 nF, 10 nF and 100 nF) and gap voltage (80 V, 95 V and 110 V). The Taguchi method was used to optimize the mentioned output parameters, while ANOVA (analysis of variance) described the significance and contribution of capacitance and gap voltage. Grey relation analysis (GRA) was conducted to perform multiple output optimization. For antibacterial response, cultivations of B. subtilis, E. coli, P. aeruginosa and S. aureus bacteria on treated surfaces for 72 h were performed. As the results, optimal values of MRR, kerf width, crater area, average surface roughness and microhardness were equal to 0.0637 mm³/min, 93.0 μm, 21.8 μm², 0.348 μm and 442 HV, respectively. Meanwhile, μ-WEDM treatment improved antibacterial properties while the highest antibacterial response was achieved at the lowest average surface roughness resulting in least biofilm formation on treated surfaces. Full article

(This article belongs to the Special Issue Advances in Surface Treatment and Coating Technology of Metallic Materials)

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11 pages, 24409 KiB

Open AccessArticle

Effect of Bismuth Content and Heating Rate on MnS Inclusions in Free-Cutting Steel

by Chunlu Xie, Hongmei Zhang, Gang Zhao, Xiangyu Li, Hongnan Li, Guoao Yu and Zhengyi Jiang

Metals 2024, 14(6), 713; https://doi.org/10.3390/met14060713 - 16 Jun 2024

Viewed by 340

Abstract

In this paper, the influence of bismuth content and heating rate on the morphology of MnS inclusions in bismuth-containing free-cutting steel during heating was investigated through in situ observation experiments and 3D electrolytic corrosion experiments. By observing the microscopic morphology of inclusions in [...] Read more.

In this paper, the influence of bismuth content and heating rate on the morphology of MnS inclusions in bismuth-containing free-cutting steel during heating was investigated through in situ observation experiments and 3D electrolytic corrosion experiments. By observing the microscopic morphology of inclusions in the original sample, it was found that MnS inclusions in the sample were rod-shaped, spherical, irregular, small in size, and mostly clustered at the grain boundary in the form of chains and divergences. With the addition of bismuth, MnS inclusions of a larger size appear in the steel, and the inclusions distributed at grain boundaries are also reduced. When bismuth (0.010~0.020%) is added to the steel, MnS is mainly spherical and uniformly dispersed in the steel matrix. If the bismuth content is too high, the inclusions aggregate. Through in situ observations of the inclusions in the sample, it was found that the addition of bismuth in the heating process delays the appearance of ferrite grain boundaries and contributes to the spheroidization of MnS inclusions. Mn and S elements can fully diffuse slowly in the matrix with a heating rate below 1 °C/s and a long holding time (300 s), which provides the possibility for the spheroidization of MnS inclusions. Full article

(This article belongs to the Special Issue Modeling and Simulation of Multiphase Transport Phenomena in Process Metallurgy)

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13 pages, 1503 KiB

Open AccessArticle

Effect of Cobalt on the Microstructure of Fe-B-Sn Amorphous Metallic Alloys

by Daniel G. Grey, Martin Cesnek, Marek Bujdoš and Marcel B. Miglierini

Metals 2024, 14(6), 712; https://doi.org/10.3390/met14060712 - 16 Jun 2024

Viewed by 403

Abstract

Fe₇₈B₁₅Sn₇ and (Fe₃Co₁)₇₈B₁₅Sn₇ amorphous metallic alloys were prepared using the method of planar flow casting. The amorphous nature of ribbons containing 7 at. % Sn was verified by X-ray [...] Read more.

Fe₇₈B₁₅Sn₇ and (Fe₃Co₁)₇₈B₁₅Sn₇ amorphous metallic alloys were prepared using the method of planar flow casting. The amorphous nature of ribbons containing 7 at. % Sn was verified by X-ray diffraction. The resulting chemical composition was checked by flame atomic absorption spectroscopy and by mass spectrometry with inductively coupled plasma. The microstructure of the as-quenched metallic glasses was investigated by 57-Fe and 119-Sn Mössbauer spectrometry. The experiments were performed with transmission geometry at 300 K, 100 K, and 4.2 K, and in an external magnetic field of 6 T. The replacement of a quarter of the Fe by Co did not cause significant modifications of the hyperfine interactions in the 57-Fe nuclei. The observed minor variations in the local magnetic microstructure were attributed to alterations in the topological short-range order. However, the in-field 57-Fe Mössbauer spectra indicated a misalignment of the partial magnetic moments. On the other hand, the presence of Co considerably affected the local magnetic microstructure of the 119-Sn nuclei. This was probably due to the higher magnetic moment of Co, which induces transfer fields and polarization effects on the diamagnetic Sn atoms. Full article

(This article belongs to the Special Issue Magnetic Properties Analysis of Amorphous and Partially Crystallized Alloys)

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17 pages, 9717 KiB

Open AccessArticle

Metallurgical Defects and Roughness Investigation in the Laser Powder Bed Fusion Multi-Scanning Strategy of AlSi10Mg Parts

by Alberto Boschetto, Luana Bottini and Daniela Pilone

Metals 2024, 14(6), 711; https://doi.org/10.3390/met14060711 - 16 Jun 2024

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Abstract

Laser Powder Bed Fusion is the most attractive additive manufacturing technology for its capability to produce metal components with complex geometry. One of the main drawbacks is the poor surface roughness. In this work, different scan strategies and process parameters were studied and [...] Read more.

Laser Powder Bed Fusion is the most attractive additive manufacturing technology for its capability to produce metal components with complex geometry. One of the main drawbacks is the poor surface roughness. In this work, different scan strategies and process parameters were studied and their effect on surface roughness, alloy microstructure, and metallurgical defects were discussed. The results highlighted that only tailored process conditions could combine acceptable roughness and absence of metallurgical defects. For the upskin, it has been seen that, although by increasing the Volumetric Energy Density value the Ra decreases, Volumetric Energy Density values higher than 69 J/mm³ determine meltpool instability with consequent formation of gas defects in the subsurface area. Similarly, by increasing the Linear Energy Density value, the Ra of the lateral surfaces decreases, but above 0.37 J/mm, metallurgical defects form in the subsurface area. This study also highlighted that the proposed process involves only a contained increase of the production times. In fact, the evaluation of the increased production times, related to the adoption of this multi-scanning strategy, is of fundamental importance to consider if the proposed process can be advantageously applied on an industrial scale. Full article

(This article belongs to the Special Issue Progress in Laser Advanced Manufacturing)

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19 pages, 25766 KiB

Open AccessArticle

Effect of Roller Burnishing and Slide Roller Burnishing on Fatigue Strength of AISI 304 Steel: Comparative Analysis

by Galya Duncheva, Jordan Maximov, Angel Anchev, Vladimir Dunchev, Kalin Anastasov and Yaroslav Argirov

Metals 2024, 14(6), 710; https://doi.org/10.3390/met14060710 - 15 Jun 2024

Viewed by 265

Abstract

The new slide roller burnishing (SRB) method has been developed to produce mirror-like surfaces. Unlike conventional roller burnishing (RB), SRB is implemented through a unique device that allows the axes of the deforming roller and the rotary workpiece to cross, resulting in a [...] Read more.

The new slide roller burnishing (SRB) method has been developed to produce mirror-like surfaces. Unlike conventional roller burnishing (RB), SRB is implemented through a unique device that allows the axes of the deforming roller and the rotary workpiece to cross, resulting in a relative sliding velocity that can be controlled (in magnitude and direction) by varying the crossing angle. In the present work, the effect of SRB on the fatigue behavior of AISI 316 steel fatigue specimens was investigated by comparing it with conventional RB using the following basic correlation in surface engineering: finishing–surface integrity (SI)–operating behavior. To obtain a more representative picture of the comparison, we implemented each method (RB and SRB) with two combinations of governing factors—(A) a radius of the roller toroidal surface of 3 mm, a burnishing force of 250 N, and a feed rate of 0.05 mm/rev (RB-A and SRB-A), and (B) a radius of the roller toroidal surface of 4 mm, a burnishing force of 550 N, and a feed rate of 0.11 mm/rev (RB-B and SRB- B). Both SRB-A (a crossing angle of –45°) and SRB-B (a crossing angle of –30°) achieved mirror-finish surfaces. SRB-B lead to the greatest fatigue strength and, thus, the longest fatigue life among all tested processes. SRB-B created the deepest zone (>0.5 mm) with residual compressive macro-stresses and a clearly defined modified surface layer, whose thickness of more than 20 μm is about twice that created by the other three processes. Full article

(This article belongs to the Special Issue Fatigue Properties of Surface Modified Metallic Materials (Volume II))

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22 pages, 12938 KiB

Open AccessArticle

Digital Model of Automatic Plate Turning for Plate Mills Based on Machine Vision and Reinforcement Learning Algorithm

by Chunyu He, Song Xue, Zhiqiang Wu, Zhong Zhao and Zhijie Jiao

Metals 2024, 14(6), 709; https://doi.org/10.3390/met14060709 - 14 Jun 2024

Viewed by 327

Abstract

Plate turning is an essential step in the plate rolling process. The traditional control mode relies on the manual observation of billets and mainly manual operation. Manual plate turning becomes an external disturbance of the automatic control system of plate mills, which reduces [...] Read more.

Plate turning is an essential step in the plate rolling process. The traditional control mode relies on the manual observation of billets and mainly manual operation. Manual plate turning becomes an external disturbance of the automatic control system of plate mills, which reduces the reproducibility and accuracy of the rolling process. The automatic plate turning function is urgently needed to improve the control level of the rolling line. In this paper, based on the improved image processing algorithm, the position and angle information of the billet conversion process are detected in real time, and the real-time processing of detection data in a complex production environment is realized. Based on the change in the billet rotation angle in the actual plate turning process, a mathematical model is constructed to simulate the plate turning process. On this basis, the digital model and optimization algorithm for automatic plate turning based on reinforcement learning are established, and the automatic optimization of plate turning speed and accuracy is completed. The field application of data-driven plate turning systems replaces manual plate turning control. The plate turning angle detection error of the system is ≤2°. The average plate turning time of each billet is greatly shortened compared with manual plate turning mode, and the fastest time can be shortened by more than 1 s, which greatly improves the production efficiency and is of great significance for improving the automatic control level and digital upgrade of plate mills. Full article

(This article belongs to the Special Issue Advanced Applications of Artificial Intelligence in Metallic Materials Processing)

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11 pages, 2477 KiB

Open AccessArticle

Effect of Incorporation of Sulfation in Columnar Modeling of Oxidized Copper Minerals on Predictions of Leaching Kinetics

by Elena Bruce, Rossana Sepúlveda, Jonathan Castillo and Manuel Saldana

Metals 2024, 14(6), 708; https://doi.org/10.3390/met14060708 - 14 Jun 2024

Viewed by 333

Abstract

Mathematical modeling of columnar leaching is a useful tool for predicting and evaluating the kinetics of copper extraction. One commonly used model for this process is the shrinking core model (SCM). In this study, the aim was to develop a model for column [...] Read more.

Mathematical modeling of columnar leaching is a useful tool for predicting and evaluating the kinetics of copper extraction. One commonly used model for this process is the shrinking core model (SCM). In this study, the aim was to develop a model for column leaching of oxidized copper ore based on the SCM, which incorporates the ore sulfation stage before leaching. In sulfation and leaching laboratory-scale tests, we studied the effect of acid dosage (at 22.8, 34.2, and 45.6 kg/t), humidity (at 90%, 100%, and 110% of the saturation humidity of the mineral), ore granulometry (−3/4″ and −3/8″), and rest time (at 24, 48, 72, and 96 h) on sulfation. We found that the highest sulfation reached 49.7% for both granulometries in studies. In the column tests, the effects of acid dosage (at 34.2, 45.6 kg/t), ore granulometry (−3/4″, −3/8″), and rest time (at 24, 48 h) were studied. When the SCM was applied to these tests, we obtained fit qualities within 63.4% and 74.9%. By incorporating the sulfation factor into the SCM predictions, we observed an average increase in adjustment between 24% and 28%. This method is effective for minerals and operating conditions different from the ones studied. Full article

(This article belongs to the Special Issue Advances in Mineral Processing and Hydrometallurgy II)

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15 pages, 3713 KiB

Open AccessArticle

The Initial Assessment of the Possibility of Simulation Fire Standard Curve in the Electric Furnace with the Assessment of Chemical Composition Changes in Steel after Cooling Phase

by Katarzyna Kubicka, Michał Szczecina, Mariusz Suckert and Tomasz Suckert

Metals 2024, 14(6), 707; https://doi.org/10.3390/met14060707 - 14 Jun 2024

Viewed by 312

Abstract

The article focuses on analyzing changes in the chemical composition of steel samples after the cooling phase. A few distinct types of samples made of St3S steel were heated in an electric resistance furnace for 1 h. The temperature in the following minutes [...] Read more.

The article focuses on analyzing changes in the chemical composition of steel samples after the cooling phase. A few distinct types of samples made of St3S steel were heated in an electric resistance furnace for 1 h. The temperature in the following minutes of the furnace work was programmed to reflect the standard fire curve defined in the Eurocode in the best possible way. The box-type electric furnace was used. There were three series of samples, and each of them was cooled down in diverse ways: (a) in the water, (b) in the polymer cooling medium AQUA-QUENCH^® 320, and (c) in the furnace. After that, the chemical composition of diverse types of samples with various kinds of cooling was checked. This task was realized using a laser elementary analysis microscope with the EA-300 head. The investigation allowed the authors to draw the following conclusions: the electric furnace may be used to simulate an increase in temperature with fire duration according to standard fire curve only in the phase of fully developed fire situation; the EA-300 head for laser elementary analysis allows checking of the chemical composition of investigated elements very quickly (in a few seconds). Full article

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

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