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Metals, Volume 14, Issue 6 (June 2024) – 120 articles

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27 pages, 2496 KiB  
Article
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 (registering DOI) - 18 Jun 2024
Viewed by 88
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
11 pages, 8743 KiB  
Article
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 161
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 αs/β phase boundaries, which are the primary reasons for its higher strength. Simultaneously, the excellent coordination in the deformation ability between the lamellar αs 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 αs 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  
Article
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 175
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
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14 pages, 28186 KiB  
Article
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 214
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
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18 pages, 7838 KiB  
Article
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 258
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
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15 pages, 4992 KiB  
Article
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 191
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
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21 pages, 29925 KiB  
Article
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 218
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
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13 pages, 8954 KiB  
Article
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 176
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, 3297 KiB  
Article
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 353
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)
20 pages, 9844 KiB  
Article
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 285
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
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11 pages, 24409 KiB  
Article
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 211
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
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13 pages, 1503 KiB  
Article
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 264
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
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17 pages, 9717 KiB  
Article
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
Viewed by 204
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  
Article
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 165
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  
Article
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 206
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
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11 pages, 2477 KiB  
Article
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 219
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  
Article
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 236
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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23 pages, 20681 KiB  
Article
Formation of Stainless Steel Welded Joints Produced with the Application of Laser and Plasma Energy Sources
by Vitalii Shevchenko, Volodymyr Korzhyk, Shiyi Gao, Vladyslav Khaskin, Detao Cai, Ziyi Luo, Yevhenii Illiashenko, Viktor Kvasnytskyi and Andrii Perepichay
Metals 2024, 14(6), 706; https://doi.org/10.3390/met14060706 - 14 Jun 2024
Viewed by 255
Abstract
The objective of this study is to investigate the formation of the structure and stress–strain state in the joints of AISI 304 stainless steel with a thickness of 2 mm and produced by welding with laser and plasma energy sources. It is established [...] Read more.
The objective of this study is to investigate the formation of the structure and stress–strain state in the joints of AISI 304 stainless steel with a thickness of 2 mm and produced by welding with laser and plasma energy sources. It is established that the microhardness and parameters of the grain and subgrain structures of the welded joint material differ with respect to the dimensions of crystallites, grains, and subgrains according to the welding process. It is shown that, in terms of structure formation, including substructural features, the most favorable structures of 2 mm AISI 304 welded joints are formed by laser–plasma welding. It is predicted that the residual stressed state is less localized with the application of laser–plasma welding than laser welding, and it is characterized by a lower level of residual stresses compared to plasma welding. In all the cases, the maximal stress values are concentrated in the HAZ, and the value obtained using laser–plasma welding is in an intermediate position (431.7 MPa) between those of the laser (443 MPa) and plasma (413.7 MPa) processes. With laser–plasma and laser welding, displacements (deformations) are minimal and close to 0.2 mm. The method of electron speckle interferometry was used, and the results reveal that the error between the calculated and experimental values of equivalent stresses is no more than 6%, which is acceptable. The results of mechanical testing show that, under uniaxial tension, the strength of the welded joints made of AISI 304 steel using laser–plasma and laser welding is the highest and equal to 97% of that of the base metal. Full article
(This article belongs to the Special Issue Advanced Laser Welding Technologies for Metals and Alloys)
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15 pages, 3890 KiB  
Article
Next-Generation Lubricity in Deep Drawing: The Synergistic Benefits of PIL and Talc on Water-Based Lubricants
by Victor Velho de Castro, Cristiano Ev, Leandro Câmara Noronha, Matheus Bullmann, Louise Etcheverry, Leonardo Moreira dos Santos, Rafael Marquetto Vargas, Silvana Mattedi, Roberto Moreira Schroeder and Célia de Fraga Malfatti
Metals 2024, 14(6), 705; https://doi.org/10.3390/met14060705 - 14 Jun 2024
Viewed by 249
Abstract
This study aims to assess the effectiveness of water-based formulations featuring m-2HEAOL and talc particles in deep drawing applications. The coefficient of friction (COF) was measured through bending under tension (BUT) tests, while the interaction mechanism between protic ionic liquid (PIL) and talc [...] Read more.
This study aims to assess the effectiveness of water-based formulations featuring m-2HEAOL and talc particles in deep drawing applications. The coefficient of friction (COF) was measured through bending under tension (BUT) tests, while the interaction mechanism between protic ionic liquid (PIL) and talc particles was analysed using FTIR, XPS, and TGA analyses. The results indicate that the formulation containing 8 wt% PIL and 0.5 wt% talc exhibited the best lubricating performance. This was due to the interaction of the PIL oleate molecules with the Mg found in the talc basal layer, which enhanced the cleavage capacity of this mineral, ultimately improving the lubricity of the formulation. Full article
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14 pages, 4472 KiB  
Article
Design and Mechanical Performance Evaluation of WE43 Magnesium Alloy Biodegradable Stents via Finite Element Analysis
by Jiaxuan Chen, Fang Dong and Sheng Liu
Metals 2024, 14(6), 704; https://doi.org/10.3390/met14060704 - 14 Jun 2024
Viewed by 264
Abstract
The emergence of biodegradable stents addresses the limitations of the long-term presence of permanent bare metal stents in the human body. Following implantation, these stents can significantly reduce the occurrence of chronic complications such as inflammation and thrombosis, thus becoming a mainstream approach [...] Read more.
The emergence of biodegradable stents addresses the limitations of the long-term presence of permanent bare metal stents in the human body. Following implantation, these stents can significantly reduce the occurrence of chronic complications such as inflammation and thrombosis, thus becoming a mainstream approach in the treatment of interventional cardiovascular diseases. Currently, the materials used for biodegradable stents are typically polymers. However, the inherent properties of the materials dictate that polymer stents exhibit lower mechanical performance and biocompatibility. Magnesium alloy materials, on the basis of their biodegradability, exhibit superior mechanical performance when compared to polymers, possessing the potential to address this issue. However, the presence of stress concentration in the stent structure necessitates further designs and mechanical performance analyses of magnesium alloy stents. In this work, a biodegradable stent based on WE43 alloy is designed. The stent incorporates the micro-protrusion structure to enhance the mechanical performance. Furthermore, to evaluate the clinical applicability of the stent, the mechanical performance of the biodegradable magnesium alloy stent is conducted through finite element analysis (FEA). The results show that the maximum equivalent stress in all four aspects is below the ultimate tensile strength of 370 MPa for the WE43 magnesium alloy, demonstrating excellent mechanical performance. Additionally, after crimping and expansion, the radial support strength and radial support force reached 780 mN/mm and 1.56 N, respectively. Compared to the advanced reported stent structures, the radial support strength and radial support force are enhanced by 13% and 47%, respectively. Additionally, flexibility analysis indicated that the flexibility of the stent design in this study is improved by a factor of 9.76, ensuring the stent’s capability to navigate through complex vasculature during implantation. Full article
(This article belongs to the Special Issue Modeling, Simulation and Experimental Studies in Metal Forming)
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20 pages, 9131 KiB  
Article
Effect of Ti Addition on the Hot-Tearing Susceptibility of the AlSi5Cu2Mg Alloy
by Marek Matejka, Dana Bolibruchová and Martina Sýkorová
Metals 2024, 14(6), 703; https://doi.org/10.3390/met14060703 - 14 Jun 2024
Viewed by 240
Abstract
The aluminum alloy AlSi5Cu2Mg finds application in the production of high-stress cylinder head castings. The AlSi5Cu2Mg alloy is specific for its high susceptibility to hot tearing. One effective way to reduce the susceptibility of Al-Si-Cu-Mg alloys to hot tearing is by grain refining. [...] Read more.
The aluminum alloy AlSi5Cu2Mg finds application in the production of high-stress cylinder head castings. The AlSi5Cu2Mg alloy is specific for its high susceptibility to hot tearing. One effective way to reduce the susceptibility of Al-Si-Cu-Mg alloys to hot tearing is by grain refining. The AlSi5Cu2Mg alloy is designed with a specific chemical composition that significantly limits the Ti content to a maximum of 0.03 wt.%. This limitation practically limits the use of standard Al-Ti-B-based refiners. The present work focuses on the investigation of the influence of graded Ti addition on the susceptibility of the AlSi5Cu2Mg alloy to hot tearing. The Ti addition was deliberately chosen beyond the manufacturer’s recommendation (0.1, 0.2, 0.3 wt.%). The solidification process of the experimental alloys with Ti addition was evaluated in this research. On the basis of the thermal analysis, it was shown that due to the addition of Ti, the solidification interval of the AlSi5Cu2Mg alloy increases. An increase in the solidification interval is often associated with an increase in the susceptibility to tearing. The susceptibility of the experimental alloys to hot tearing was evaluated qualitatively and quantitatively. Based on the quantitative and qualitative evaluation, it was shown that the addition of Ti reduces the susceptibility of the AlSi5Cu2Mg alloy to hot tearing. A positive refining effect of Ti on the primary α-(Al) phase was demonstrated by microstructural evaluation. Based on this research, it was shown that despite the increase in the solidification interval due to the addition of Ti, the susceptibility of the aluminum alloy to the formation of hot tears is reduced due to the better filling of the material in the interdendritic spaces. Full article
(This article belongs to the Special Issue Light Alloy and Its Application II)
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17 pages, 16718 KiB  
Article
The Mechanism of Forming Hollow Shafts with Constant Wall Thickness by Three-Roll Skew Rolling
by Song Zhang, Xuedao Shu, Jitai Wang, Zixuan Li, Haijie Xu, Yingxiang Xia, Zbigniew Pater, Janusz Tomczak and Tomasz Bulzak
Metals 2024, 14(6), 702; https://doi.org/10.3390/met14060702 - 14 Jun 2024
Viewed by 221
Abstract
To solve the problem of the long forming process for hollow shafts with constant wall thickness (HSCWT), a new process for forming HSCWT, namely three-roll skew rolling, has been proposed. First, the working principle of the three-roll skew rolling process is presented. Then, [...] Read more.
To solve the problem of the long forming process for hollow shafts with constant wall thickness (HSCWT), a new process for forming HSCWT, namely three-roll skew rolling, has been proposed. First, the working principle of the three-roll skew rolling process is presented. Then, the finite element model (FEM) of the three-roll skew rolling HSCWT is established. The strain-stress field and temperature field distribution rules of the three-roll skew rolling HSCWT are analyzed with FEM. The stress-strain field of the rolled piece is distributed uniformly along the axial direction but not uniformly along the radial direction. The variation of the temperature field is related to the axial traction velocity. The greater the axial traction velocity, the smaller the variation of the temperature field. The temperature of rolled pieces varies within 100 °C during rolling. Finally, the three-roll skew rolling experiment of the HSCWT is carried out. The results show that the three-roll skew rolling process can form HSCWT. The temperature field of the three-roll skew rolling HSCWT is evenly distributed. The selection of larger axial traction velocity is conducive to the forming of rolled pieces. The three-roll skew rolling technology has achieved near constant temperature forming of HSCWT. Full article
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19 pages, 10137 KiB  
Article
Tribological Behavior Analysis of Valve Plate Pair Materials in Aircraft Piston Pumps and Friction Coefficient Prediction Using Machine Learning
by Yongjie Wang, Rui Nie, Xiaochao Liu, Shijie Wang and Yunlong Li
Metals 2024, 14(6), 701; https://doi.org/10.3390/met14060701 - 14 Jun 2024
Viewed by 251
Abstract
To address the problem of tribological failure in an aircraft piston pump valve plate pair, the friction and wear properties of the valve plate pair materials (W9Mo3Cr4V-HAl61-4-3-1) of an axial piston pump at a certain speed and load were studied using a disc-ring [...] Read more.
To address the problem of tribological failure in an aircraft piston pump valve plate pair, the friction and wear properties of the valve plate pair materials (W9Mo3Cr4V-HAl61-4-3-1) of an axial piston pump at a certain speed and load were studied using a disc-ring tester under lubrication with No. 15 aviation hydraulic oil. The results show that the friction coefficient (COF) fluctuated in the range of 0.019~0.120 when the load (L) increased from 30 N to 120 N, and the speed increased from 100 r/min to 500 r/min. With the increase in the rotational speed, the COF of the valve plate pair decreased first and then increased. When the rotation speed (V) was 300 r/min, the relative COF was the smallest. Under L lower than 60 N, abrasive wear was the main wear mechanism. Under L higher than 90 N, the main wear mechanism was adhesive wear but mild oxidation wear also occurred. In addition, based on the V, L, radius (R), and test duration (T), which affected COF, the random forest regression (RFR) algorithm, the bagging regression (BR) algorithm, and the extra trees regression (ETR) algorithm were used as machine learning methods to predict the COF of the valve plate pair. Mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2) were used to evaluate its performance, with the results showing that the ETR prediction model was the best method for predicting COF. The results of the machine learning also showed that the contributions of V, L, R, and T were 43.56%, 36.76%, 13.13%, and 6.55%, respectively, indicating that V had the greatest influence on the COF of the W9Mo3Cr4V/HAl61-4-3-1 friction pair. This study is expected to provide support for the rapid development of new valve plate pair materials. Full article
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16 pages, 9034 KiB  
Article
Combinatorial Design of an Electroplated Multi-Principal Element Alloy: A Case Study in the Co-Fe-Ni-Zn Alloy System
by Péter Nagy, László Péter, Tamás Kolonits, Attila Nagy and Jenő Gubicza
Metals 2024, 14(6), 700; https://doi.org/10.3390/met14060700 - 14 Jun 2024
Viewed by 248
Abstract
Multi-principal element alloys (MPEAs) are at the forefront of materials science due to their large variety of compositions, which can yield unexplored properties. Mapping the structure and properties of a compositional MPEA library in a reasonable time can be performed with the help [...] Read more.
Multi-principal element alloys (MPEAs) are at the forefront of materials science due to their large variety of compositions, which can yield unexplored properties. Mapping the structure and properties of a compositional MPEA library in a reasonable time can be performed with the help of gradient samples. This type of specimens has already been produced in both bulk and layer forms. However, combinatorial MPEA coatings have not been synthesized by electroplating, although this method has a great potential to deposit a coating on components with complex shapes. In this study, a combinatorial Co-Fe-Ni-Zn coating with the thickness of 4 μm was synthesized by electrodeposition. The material exhibited a well-defined Zn gradient; therefore, the investigation of the effect of Zn concentration on the microstructure and mechanical properties was feasible without the production of an excessively large number of specimens. The Zn concentration was controlled laterally through mass transfer due to the unique geometry of the substrate, and it covered a concentration range of 18–44 at%. The chemical and phase compositions as well as the morphology of the as-processed samples were investigated in multiple locations using X-ray diffraction and scanning electron microscopy. The mechanical performance was characterized by nanoindentation. It was found that for any composition, the structure is face-centered cubic and the lattice constant scaled with the Zn concentration of the deposit. The hardness and the elastic modulus were consistent with values of about 4.5 and 130 GPa, respectively, in the Zn concentration range of 25–44 at%. Full article
(This article belongs to the Section Crystallography and Applications of Metallic Materials)
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11 pages, 4789 KiB  
Article
Harnessing Microwave Technology for Enhanced Recovery of Zinc from Industrial Clinker
by Bagdaulet Kenzhaliyev, Tatiana Surkova, Ainur Berkinbayeva, Zhazira Baltabekova and Kenzhegali Smailov
Metals 2024, 14(6), 699; https://doi.org/10.3390/met14060699 - 13 Jun 2024
Viewed by 283
Abstract
This article presents a cutting-edge approach to microwave-assisted processing aimed at enhancing the efficiency of zinc extraction from materials characterized by a high degree of processing complexity. The described technique encompasses two sequential phases: phase transformation under microwave irradiation and leaching in sulfuric [...] Read more.
This article presents a cutting-edge approach to microwave-assisted processing aimed at enhancing the efficiency of zinc extraction from materials characterized by a high degree of processing complexity. The described technique encompasses two sequential phases: phase transformation under microwave irradiation and leaching in sulfuric acid at ambient temperature. During the phase transformation, implemented through the application of microwave energy, insoluble zinc phases undergo a controlled transition. The experimental results confirm that microwave calcination at 600 °C for 5–7 min is effective for converting ZnS to ZnO without the formation of ZnO∙Fe2O3. Zinc extraction from the clinker reached 46.47% after treatment with microwave radiation at a power of 25 kW for the specified duration. Thus, this study opens up prospects for environmentally friendly zinc extraction from challenging-to-process resources. Full article
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13 pages, 11904 KiB  
Article
The Microstructure and Properties of Laser-Cladded Ni-Based and Co-Based Alloys on 316L Stainless Steel
by Tao Fang, Feng Huang, Xuzheng Qian and Wen Zhan
Metals 2024, 14(6), 698; https://doi.org/10.3390/met14060698 - 13 Jun 2024
Viewed by 198
Abstract
To extend the service life of 316L stainless steel components in harsh environments, this study utilized laser cladding technology to enhance the hardness, wear resistance, and corrosion resistance of the 316L stainless steel surface. Nickel-based and cobalt-based cladding layers were prepared on the [...] Read more.
To extend the service life of 316L stainless steel components in harsh environments, this study utilized laser cladding technology to enhance the hardness, wear resistance, and corrosion resistance of the 316L stainless steel surface. Nickel-based and cobalt-based cladding layers were prepared on the surface of the 316L stainless steel, and the microstructure and phases of the layers were analyzed using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. In addition, the hardness of the substrate and the cladding layers was tested with a microhardness tester, the frictional wear performance was tested with a pin on disc wear tester, and the corrosion resistance was tested with an electrochemical workstation. The experimental results indicate that the nickel-based cladding layer primarily comprises the γ-(Fe, Ni), Cr7C3, and Ni3Si phases, with equiaxed and dendritic grains being the predominant morphologies. By contrast, the cobalt-based cladding layer mainly comprises the γ-Co, Cr7C3, and Co7W6 phases, with columnar and dendritic grains being the predominant morphologies. Both cladding layers displayed a significantly better microhardness, wear resistance, and corrosion resistance than the substrate. Between the two cladding layers, the nickel-based cladding layer demonstrated a superior microhardness, whereas the cobalt-based cladding layer slightly outperformed in wear resistance and corrosion resistance. The findings from our results are important for understanding the performance of laser-cladding layers and laying a scientific basis for the promotion and optimization of laser cladding technology in industrial applications. Moreover, our results showed that laser cladding technology is increasingly important in extending the service life of components and improving the material performance. Full article
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14 pages, 11395 KiB  
Article
A New Lead-Free Copper Alloy CuAl8Fe5Ni4Zn4Sn1 for Plain Bearings and Its Strengthening Mechanisms
by Björn Reetz and Tileman Münch
Metals 2024, 14(6), 697; https://doi.org/10.3390/met14060697 - 12 Jun 2024
Viewed by 265
Abstract
CuAl8Fe5Ni4Zn4Sn1 (OF 2238) is a new lead-free copper alloy for plain-bearing applications that was first officially presented in a scientific journal in 2020. Soon after its invention, the use of the alloy for connecting rod bushings in heavy-duty internal combustion engines was promoted [...] Read more.
CuAl8Fe5Ni4Zn4Sn1 (OF 2238) is a new lead-free copper alloy for plain-bearing applications that was first officially presented in a scientific journal in 2020. Soon after its invention, the use of the alloy for connecting rod bushings in heavy-duty internal combustion engines was promoted and validated with customers. The aim of this article is to describe the material properties of the new alloy in more detail than previously and explain how the advantageous properties of CuAl8Fe5Ni4Zn4Sn1 are generated. At the beginning of this article, the general development trends in the field of copper alloys for sliding applications are presented, into which the new alloy from this publication can be classified. In the main part of this publication, the authors go through the production chain of CuAl8Fe5Ni4Zn4Sn and show how the entire manufacturing process contributes to obtaining a material with a combination of high strength, ductility and sufficient toughness. This starts with fine microstructures after casting, followed by homogenisation and refinement during hot extrusion and work hardening chiefly during cold drawing. What is most surprising, however, is the finding that a strong hardening effect can be achieved in the new alloy by precipitation of fine κ-phase at temperatures of about 400 °C and air cooling without prior solution treatment. These results make it clear that there is great potential for further material developments to support material efficiency and even to expand the application limits. Full article
(This article belongs to the Special Issue Advanced Performance of Copper Alloys)
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18 pages, 51050 KiB  
Article
Effect of Copper and Nickel Content on the Corrosion Mechanisms in Ferritic Matrix Gray Cast Irons under Simulated Marine Environments
by Hector Bruna, Rodrigo Allende-Seco, Alfredo Artigas, Alberto Monsalve and Christian Sánchez
Metals 2024, 14(6), 696; https://doi.org/10.3390/met14060696 - 12 Jun 2024
Viewed by 281
Abstract
This article investigated the influence of copper (Cu) and nickel (Ni) on atmospheric corrosion in gray cast iron under simulated marine conditions. The goal was to compare the effect of Cu and Ni addition in castings with weathering steels. Selected alloys were cast, [...] Read more.
This article investigated the influence of copper (Cu) and nickel (Ni) on atmospheric corrosion in gray cast iron under simulated marine conditions. The goal was to compare the effect of Cu and Ni addition in castings with weathering steels. Selected alloys were cast, cut, prepared, and heat-treated for microstructure homogenization. Accelerated corrosion tests were conducted using a salt spray chamber. Corroded samples were analyzed for corrosion thickness and deposits using scanning electron microscopy, X-ray diffraction, and electrochemical techniques. The results indicate that alloying elements significantly affect corrosion processes. In the long-term, Cu had a greater impact on the corrosion mechanisms than Ni. Both Cu and Ni exhibited similar effects on the corrosion mechanisms in gray cast iron and weathering steels. In the initial and final stages, the behavior was comparable to that of weathering steels, but in the intermediate stage, it differed from the literature, suggesting the presence of an additional mechanism between these stages. Full article
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18 pages, 867 KiB  
Article
On Least Squares Support Vector Regression for Predicting Mechanical Properties of Steel Rebars
by Renan Bessa, Guilherme Alencar Barreto, David Nascimento Coelho, Elineudo Pinho de Moura and Raphaella Hermont Fonseca Murta
Metals 2024, 14(6), 695; https://doi.org/10.3390/met14060695 - 12 Jun 2024
Viewed by 252
Abstract
Aiming at ensuring the quality of the product and reducing the cost of steel manufacturing, an increasing number of studies have been developing nonlinear regression models for the prediction of the mechanical properties of steel rebars using machine learning techniques. Bearing this in [...] Read more.
Aiming at ensuring the quality of the product and reducing the cost of steel manufacturing, an increasing number of studies have been developing nonlinear regression models for the prediction of the mechanical properties of steel rebars using machine learning techniques. Bearing this in mind, we revisit this problem by developing a design methodology that amalgamates two powerful concepts in parsimonious model building: (i) sparsity, in the sense that few support vectors are required for building the predictive model, and (ii) locality, in the sense that simpler models can be fitted to smaller data partitions. In this regard, two regression models based on the Least Squares Support Vector Regression (LSSVR) model are developed. The first one is an improved sparse version of the one introduced in a previous work. The second one is a novel local LSSVR-based regression model. The task of interest is the prediction of four output variables (the mechanical properties YS, UTS, UTS/YS, and PE) based on information about its chemical composition (12 variables) and the parameters of the heat treatment rolling (6 variables). The proposed LSSVR-based regression models are evaluated using real-world data collected from steel rebar manufacturing and compared with the global LSSVR model. The local sparse LSSVR approach was able to consistently outperform the standard single regression model approach in the task of interest, achieving improvements in the average R2 from previous studies: 5.04% for UTS, 5.19% for YS, 1.96% for UTS/YS, and 3.41% for PE. Furthermore, the sparsification of the dataset and the local modeling approach significantly reduce the number of SV operations on average, utilizing 34.0% of the total SVs available for UTS estimation, 44.0% for YS, 31.3% for UTS/YS, and 32.8% for PE. Full article
(This article belongs to the Special Issue Machine Learning Models in Metals)
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13 pages, 3851 KiB  
Article
Fracture Model of Al–Cu Alloys with Gradient Crystals Based on Crystal Plasticity
by Mao Xiao, Ji Yao and Chunyang Huang
Metals 2024, 14(6), 694; https://doi.org/10.3390/met14060694 - 12 Jun 2024
Viewed by 257
Abstract
Gradient grain structure materials with superior mechanical properties of high strength and high toughness have attracted widespread attention. Gradient materials can effectively improve toughness by constructing a microstructure from fine to coarse crystals inside the material, which has gradually become a hotspot of [...] Read more.
Gradient grain structure materials with superior mechanical properties of high strength and high toughness have attracted widespread attention. Gradient materials can effectively improve toughness by constructing a microstructure from fine to coarse crystals inside the material, which has gradually become a hotspot of attention in the academic and engineering communities. In this paper, based on the crystal plasticity intrinsic theory, dislocation density is introduced as a characterization quantity, and cohesive units are added at grain boundaries to simulate damage fractures. The results of this study reveal the fracture damage mechanism of gradient crystal structure materials, providing new ideas and methods for the design of gradient materials. Full article
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