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Metals, Volume 12, Issue 11 (November 2022) – 222 articles

Cover Story (view full-size image): The fatigue behavior of austenitic stable and metastable stainless steels with different surface morphologies was investigated regarding the VHCF regime using an ultrasonic fatigue testing system. The AISI 904L is stable against deformation-induced phase formation, while the AISI 347 is in the metastable state and shows martensite formation. The specimens from stable austenite failed in the HCF and VHCF regimes. In contrast, the metastable austenite achieved true fatigue limits and failed only in the HCF regime. Due to surface modification, an increase in the fatigue strength of metastable AISI 347 was achieved. View this paper
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38 pages, 11767 KiB  
Article
Optimal Design of Three-Stress Accelerated Degradation Test Plan for Motorized Spindle with Poor Prior Information
by Hongxun Zhao, Zhaojun Yang, Chuanhai Chen, Zhifeng Liu, Wei Luo and Chunlei Hua
Metals 2022, 12(11), 1996; https://doi.org/10.3390/met12111996 - 21 Nov 2022
Viewed by 1217
Abstract
Accurate optimal design for the test plan with limited prior information is impossible since the optimal design method of a three-stress accelerated degradation test plan for a motorized spindle is based on the determination of model parameters. In order to optimize the test [...] Read more.
Accurate optimal design for the test plan with limited prior information is impossible since the optimal design method of a three-stress accelerated degradation test plan for a motorized spindle is based on the determination of model parameters. In order to optimize the test plan with poor prior information, a “dynamic” optimal design method is proposed in this article. Firstly, a three-stress accelerated degradation model with a stress coupling term is established based on the correlation of the degradation rate of the motorized spindle, and the parameters in the model are regarded as variables to represent the deviation between the prior information and the true value of the motorized spindle when the prior information is poor. Then, based on the information theory and the sequential design method, an optimal design method of the three-stress accelerated degradation test plan of the motorized spindle with the information entropy as the objective function is proposed to realize the “dynamic” optimization of the test plan. Finally, the usability of the proposed method is verified by taking a Chinese model spindle as an example, and the validity of the method is verified by checking the model accuracy of the accelerated degradation model of the motorized spindle after the test. Full article
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13 pages, 4660 KiB  
Article
The Growth of Intermetallic Compounds and Its Effect on Bonding Properties of Cu/Al Clad Plates by CFR
by Long Li, Guangping Deng, Weiguo Zhai, Sha Li, Xiangyu Gao and Tao Wang
Metals 2022, 12(11), 1995; https://doi.org/10.3390/met12111995 - 21 Nov 2022
Cited by 4 | Viewed by 1306
Abstract
Cu/Al clad plates prepared using a corrugated + flat rolling (CFR) technique were annealed at 300–450 °C for 10–240 min. Furthermore, the interfacial diffusion behavior and the bonding properties of the Cu/Al clad plates were studied in detail. The results demonstrated that, at [...] Read more.
Cu/Al clad plates prepared using a corrugated + flat rolling (CFR) technique were annealed at 300–450 °C for 10–240 min. Furthermore, the interfacial diffusion behavior and the bonding properties of the Cu/Al clad plates were studied in detail. The results demonstrated that, at the initial stage of the annealing process, the development of the first IMCs layer was restrained by the high atomic concentration gradient in the new bonding interface zone, and the second intermetallic compounds (IMCs) layer preferentially formed in the new bonding interface zone, leading to a slight increase in the growth activation energy of the clad plates. In addition, the atoms’ diffusion behavior at the peak and trough interfaces was not significantly affected by the matrix microstructure, and there was no discernible difference in the growth activation energy at these two positions. Ultimately, it was shown that the maximum average peel strength at the peak and trough interfaces reached 53.07 N/mm and 41.23 N/mm, respectively, when annealing at 350 °C for 10 min. Full article
(This article belongs to the Special Issue Process and Numerical Simulation of Oxygen Steelmaking)
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8 pages, 1746 KiB  
Article
Inclusion Characteristics in Steel with CeO2 Nanoparticle Addition
by Hui Kong, Xiang Cheng, Shoulin Huang and Yue Qiu
Metals 2022, 12(11), 1994; https://doi.org/10.3390/met12111994 - 21 Nov 2022
Cited by 2 | Viewed by 1232
Abstract
The application of Ce oxides in oxide metallurgy has received extensive attention, but until now, the direct adding of CeO2 into molten steel to generate Ce oxides has not occurred. In this paper, a mixture of CeO2 and Si nanoparticles were [...] Read more.
The application of Ce oxides in oxide metallurgy has received extensive attention, but until now, the direct adding of CeO2 into molten steel to generate Ce oxides has not occurred. In this paper, a mixture of CeO2 and Si nanoparticles were added into molten steel. The resultant formation of micrometer scale Ce-bearing oxides confirmed its adding validity. This behavior may be interpreted as the reactivity between CeO2 and [Al], and the improved wettability between CeO2 and molten steel with the assistance of Si powder. Thus, when the quantity of CeO2 is kept constant, its added yield should increase when increasing the added quantity of Si. This was verified by the larger percentage of Ce-bearing oxides of the total oxides and the greater average content of Ce in Ce-bearing oxides after normalization. Moreover, compared with the blank sample, statistical results indicated that the oxides in CeO2-modified samples were refined, and their dispersion homogeneity was enhanced. This comparison indicates the effectiveness of the external adding method in oxide metallurgy. Full article
(This article belongs to the Topic Advanced Processes in Metallurgical Technologies)
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16 pages, 6381 KiB  
Article
Effect of Shoulder Fillet Radius on Welds in Bobbin Tool Friction Stir Welding of A1050
by Huilin Miao, Takuya Miura, Wei Jiang, Masato Okada and Masaaki Otsu
Metals 2022, 12(11), 1993; https://doi.org/10.3390/met12111993 - 21 Nov 2022
Cited by 2 | Viewed by 1437
Abstract
In this study, five bobbin tools with different shoulder fillet radii were employed for the bobbin tool friction stir welding (BT-FSW) of A1050-O sheets to systematically evaluate the effects of shoulder fillet radius on the welding defect formation, flash formation, weld thickness, grain [...] Read more.
In this study, five bobbin tools with different shoulder fillet radii were employed for the bobbin tool friction stir welding (BT-FSW) of A1050-O sheets to systematically evaluate the effects of shoulder fillet radius on the welding defect formation, flash formation, weld thickness, grain size of the stir zone, and tensile properties. The quality classifications of the joints’ appearance were summarized as process windows, and the appropriate welding condition range for each shoulder fillet radius was clarified. It was observed that an increase in the shoulder fillet radius decreased the welding defects and flash formation; however, it increased the minimum thickness of the weld except when the shoulder fillet radius was 0.5 mm. The grain size of the stir zone increased with increasing shoulder fillet radius from 0.5 mm to 6 mm. The ultimate tensile strength (UTS) of the stir zone decreased with increasing shoulder fillet radius from 0.5 mm to 1 mm, increased from 1 mm to 3 mm, and remained constant from 3 mm to 6 mm. The results indicate that a shoulder fillet radius larger than 3 mm is effective in decreasing flash formation and maintaining a constant weld thickness. Full article
(This article belongs to the Section Welding and Joining)
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10 pages, 12679 KiB  
Article
Laser Beam Welding of CubeSat 1U Structure Parts Obtained by Powder Bed Fusion
by Rafael Humberto Mota de Siqueira, Diego Javier Celentano and Milton Sergio Fernandes de Lima
Metals 2022, 12(11), 1992; https://doi.org/10.3390/met12111992 - 21 Nov 2022
Viewed by 1366
Abstract
This study contributes to a possible methodology for manufacturing CubeSats using additive manufacturing and laser beam welding. Titanium connectors were constructed by selective laser melting and electron beam melting and characterized from a topological point of view. The connectors can be joined to [...] Read more.
This study contributes to a possible methodology for manufacturing CubeSats using additive manufacturing and laser beam welding. Titanium connectors were constructed by selective laser melting and electron beam melting and characterized from a topological point of view. The connectors can be joined to titanium tubes for the construction of CubeSats via laser spot welding. The fiber laser welds exhibited full penetration using pulses with 400 J of energy. The welds showed titanium acicular martensite grains with recesses and pores. The average hardness of the cast zone was 350 HV, which is close to the hardness of the connectors (400 HV) and more rigid than that of the tubes (100 HV). Spot welding has proven to be useful in resisting forces above 2000 N, which is sufficient for CubeSat frame space applications. Full article
(This article belongs to the Special Issue Laser Welding and Welding Joint Quality Assessment - State of Art)
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11 pages, 3366 KiB  
Article
Analysis of Texture and Anisotropic Elastic Properties of Additively Manufactured Ni-Base Alloys
by Thomas Obermayer, Christian Krempaszky and Ewald Werner
Metals 2022, 12(11), 1991; https://doi.org/10.3390/met12111991 - 21 Nov 2022
Cited by 4 | Viewed by 1507
Abstract
Additive manufacturing of metallic materials generates strong crystallographic textures, leading to anisotropic elastic properties on the macroscopic scale. The impact of the processing parameters on the resulting texture requires suitable techniques for the prediction and the experimental determination of elastic properties to exploit [...] Read more.
Additive manufacturing of metallic materials generates strong crystallographic textures, leading to anisotropic elastic properties on the macroscopic scale. The impact of the processing parameters on the resulting texture requires suitable techniques for the prediction and the experimental determination of elastic properties to exploit the anisotropy in the design process. Within this study mechanical as well as microstructure based approaches are applied on a batch of specimens manufactured from IN718 by selective laser melting to assess the elastic behavior on macroscropic scale. Tensile loading experiments and the impulse excitation technique are applied for the determination of elastic properties without additional constitutive data. Furthermore, the elastic behavior is estimated from single-crystal elastic properties and texture data measured by electron backscatter diffraction and high energy X-ray diffraction. The results of the applied approaches are discussed and compared, allowing also to assess the homogeneity of the elastic properties within the batch of specimens. Full article
(This article belongs to the Special Issue Advanced Techniques for Metallurgical Characterization)
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17 pages, 9889 KiB  
Article
Macrosegregation Evolution in Eutectic Al-Si Alloy under the Influence of a Rotational Magnetic Field
by Kassab Al-Omari, András Roósz, Arnold Rónaföldi, Mária Svéda and Zsolt Veres
Metals 2022, 12(11), 1990; https://doi.org/10.3390/met12111990 - 21 Nov 2022
Cited by 1 | Viewed by 1523
Abstract
Using magnetic stirring during solidification provides a good opportunity to control the microstructure of alloys, thus controlling their physical properties. However, magnetic stirring is often accompanied by a change in local concentrations, and new structures form which could harm the physical properties. This [...] Read more.
Using magnetic stirring during solidification provides a good opportunity to control the microstructure of alloys, thus controlling their physical properties. However, magnetic stirring is often accompanied by a change in local concentrations, and new structures form which could harm the physical properties. This research paper investigated the effect of forced melt flow by a rotating magnetic field (RMF) on the macrostructure of an Al-Si eutectic alloy. To serve this purpose, Al-12.6 wt% Si alloy samples were solidified in a vertical Bridgman-type furnace equipped with a rotating magnetic inductor to induce the flow in the melt. The diameter and length of the sample are 8 mm and 120 mm, respectively. The solidification parameters are a temperature gradient (G) of 6 K/m, and the solid/liquid front velocity (v) of 0.1 mm/s. These samples were divided into parts during the solidification process, where some of these parts are solidified under the effect of RMF stirring while others are solidified without stirring. The structure obtained after solidification showed a distinct impact of stirring by RMF; new phases have been solidified which were not originally present in the structure before stirring. Besides the eutectic structure, the new phases are the primary aluminum and the primary silicon. The Si concentration and the volume fraction of each phase were measured using Energy-Dispersive Spectroscope (EDS)and new image processing techniques. The experimental results reveal that applying the RMF during the solidification has a distinct effect on the macrostructure of Al-Si eutectic alloys. Indeed, the RMF provokes macro-segregation, reduces the amount of eutectic structure, and changes the sample’s Si concentration distribution. Full article
(This article belongs to the Special Issue Solidification Process of Alloys under Magnetic Field)
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12 pages, 10933 KiB  
Article
Atomistic Investigation of Titanium Carbide Ti8C5 under Impact Loading
by Kang Xia, Haifei Zhan, Jianli Shao, Jiaqiu Wang, Zhuoqun Zheng, Xinjie Zhang and Zhiyong Li
Metals 2022, 12(11), 1989; https://doi.org/10.3390/met12111989 - 20 Nov 2022
Cited by 1 | Viewed by 1606
Abstract
Titanium carbides attract attention from both academic and industry fields because of their intriguing mechanical properties and proven potential as appealing candidates in the variety of fields such as nanomechanics, nanoelectronics, energy storage and oil/water separation devices. A recent study revealed that the [...] Read more.
Titanium carbides attract attention from both academic and industry fields because of their intriguing mechanical properties and proven potential as appealing candidates in the variety of fields such as nanomechanics, nanoelectronics, energy storage and oil/water separation devices. A recent study revealed that the presence of Ti8C5 not only improves the impact strength of composites as coatings, but also possesses significant strengthening performance as an interlayer material in composites by forming strong bonding between different matrices, which sheds light on the design of impact protection composite materials. To further investigate the impact resistance and strengthening mechanism of Ti8C5, a pilot Molecular Dynamics (MD) study utilizing comb3 potential is carried out on a Ti8C5 nanosheet by subjecting it to hypervelocity impacts. The deformation behaviour of Ti8C5 and the related impact resist mechanisms are assessed in this research. At a low impact velocity ~0.5 km/s, the main resonance frequency of Ti8C5 is 11.9 GHz and its low Q factor (111.9) indicates a decent energy damping capability, which would eliminate the received energy in an interfacial reflection process and weaken the shock waves for Ti8C5 strengthened composites. As the impact velocity increases above the threshold of 1.8 km/s, Ti8C5 demonstrates brittle behaviour, which is signified by its insignificant out-of-plane deformation prior to crack initiation. When tracking atomic Von Mises stress distribution, the elastic wave propagation velocity of Ti8C5 is calculated to be 5.34 and 5.90 km/s for X and Y directions, respectively. These figures are inferior compared with graphene and copper, which indicate slower energy delocalization rates and thus less energy dissipation via deformation is expected prior to bond break. However, because of its relatively small mass density comparing with copper, Ti8C5 presents superior specific penetration. This study provides a fundamental understanding of the deformation and penetration mechanisms of titanium carbide nanosheets under impact, which is crucial in order to facilitate emerging impact protection applications for titanium carbide-related composites. Full article
(This article belongs to the Special Issue Deformation and Fracture of Condensed Materials in Extreme Conditions)
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18 pages, 3151 KiB  
Review
Research Progress of Magnetic Field Regulated Mechanical Property of Solid Metal Materials
by Yujun Hu, Hongjin Zhao, Xuede Yu, Junwei Li, Bing Zhang and Taotao Li
Metals 2022, 12(11), 1988; https://doi.org/10.3390/met12111988 - 20 Nov 2022
Cited by 9 | Viewed by 1666
Abstract
During the material preparation process, the magnetic field can act with high intensity energy on the material without contact and affect its microstructure and properties. This non-contact processing method, which can change the microstructure and properties of material without affecting the shape and [...] Read more.
During the material preparation process, the magnetic field can act with high intensity energy on the material without contact and affect its microstructure and properties. This non-contact processing method, which can change the microstructure and properties of material without affecting the shape and size of products, has become an important technical means to develop new materials and optimize the properties of materials. It has been widely used in scientific research and industrial production. In recent years, the magnetic field assisted processing of difficult-to-deform materials or improving the performance of complex and precision parts has been rapidly and widely concerned by scholars at home and abroad. This paper reviews the research progress of magnetic field regulating the microstructure, and properties of solid metal materials. The effects of magnetic field-assisted heat treatment, magnetic field assisted stretching, and magnetic field independent treatment on the microstructure and properties of solid metal materials are introduced. The mechanism of the magnetic field effect on the properties of metal materials is summarized, and future research on the magnetic field effect on solid metal has been prospected. Full article
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17 pages, 8876 KiB  
Article
Structure and Properties of Al-Co-Cr-Fe-Ni High-Entropy Alloy Subjected to Electron–Ion Plasma Treatment
by Yurii Ivanov, Victor Gromov, Sergey Konovalov, Vladimir Shugurov, Mikhail Efimov, Anton Teresov, Elizaveta Petrikova, Irina Panchenko and Yulia Shliarova
Metals 2022, 12(11), 1987; https://doi.org/10.3390/met12111987 - 20 Nov 2022
Cited by 1 | Viewed by 1748
Abstract
High-entropy alloys (HEAs) are a new class of materials consisting of at least five elements in equiatomic or near-equiatomic ratio. HEAs are subjected to various types of surface treatment to improve their properties. One of the most promising methods of surface hardening is [...] Read more.
High-entropy alloys (HEAs) are a new class of materials consisting of at least five elements in equiatomic or near-equiatomic ratio. HEAs are subjected to various types of surface treatment to improve their properties. One of the most promising methods of surface hardening is electron beam processing. This study aims to examine the structure, elemental, and phase composition of the AlCrFeCoNi HEA surface layer after the deposition of a (B + Cr) film and irradiation with a pulsed electron beam. HEA samples of non-equiatomic composition (33.4 Al; 8.3 Cr; 17.1 Fe; 5.4 Co; 35.7 Ni, at. %), fabricated by wire-arc additive manufacturing (WAAM), were used as study objects. Modification of the HEA surface layer was carried out by a complex method combining deposition of (B + Cr) film samples on the surface and irradiation with a pulsed electron beam in an argon medium. The mode of modification was identified. It makes it possible to increase microhardness (almost two times) and wear resistance (more than five times), reduce the friction coefficient of the HEA surface layer by 1.3 times due to the decrease in the average grain size, formation of particles of borides and oxyborides of complex elemental composition, the introduction of boron atoms into the crystal lattice of HEA. Full article
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13 pages, 3871 KiB  
Article
Experimental Investigation and Numerical Simulation of the Fluidity of A356 Aluminum Alloy
by Hyeon-Sik Bang, Hyeok-In Kwon, Sung-Bean Chung, Dae-Up Kim and Min-Su Kim
Metals 2022, 12(11), 1986; https://doi.org/10.3390/met12111986 - 20 Nov 2022
Cited by 2 | Viewed by 1660
Abstract
The fluidity of A356 aluminum alloy was experimentally determined at the melt temperatures and vacuum degrees by a series of suction fluidity tests. In order to achieve different cooling rates during the test, quartz tubes, as well as stainless steel tubes, were employed [...] Read more.
The fluidity of A356 aluminum alloy was experimentally determined at the melt temperatures and vacuum degrees by a series of suction fluidity tests. In order to achieve different cooling rates during the test, quartz tubes, as well as stainless steel tubes, were employed as the fluidity channels. As the melt temperature increased from 650 to 730 °C, fluidity lengths either linearly increased from 26 to 36 cm or parabolically increased from 13 to 29 cm when quartz tubes or stainless steel tubes were employed, respectively. As the vacuum degree of the fluidity test increased from 0.005 to 0.03 MPa, fluidity increased from 25 to 43 cm in quartz tubes while the smaller increase in fluidity from 20 to 31 cm was observed in stainless steel tubes. Shorter fluidity lengths in stainless steel tubes than those in quartz tubes under the same fluidity measurement condition were due to faster solidification speed confirmed by microstructural analysis. In order to predict the fluidity of the A356 alloy obtained from the suction fluidity tests, a mathematical model was developed based on heat and mass transfer equations coupled with thermodynamic calculations by ChemApp software. The simulation results show good agreement with the fluidity length obtained in the present study. From a series of model calculations, the effects of casting parameters on the fluidity of the A356 melt were discussed. Full article
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11 pages, 3834 KiB  
Article
Structural Phase Transformation of Rail Steel in Compression
by Krestina Aksenova, Victor Gromov, Yurii Ivanov, Rongshan Qin and Ekaterina Vashchuk
Metals 2022, 12(11), 1985; https://doi.org/10.3390/met12111985 - 20 Nov 2022
Cited by 3 | Viewed by 1570
Abstract
The analysis of structure and defective substructure of rail steel in uniaxial compression to a degree of 50% is carried out. It is revealed that cold hardening has a multi-stage character and is accompanied by fragmentations of pearlite grains which is in field [...] Read more.
The analysis of structure and defective substructure of rail steel in uniaxial compression to a degree of 50% is carried out. It is revealed that cold hardening has a multi-stage character and is accompanied by fragmentations of pearlite grains which is in field as the degree of deformation increases and reaches ≈ 0.4 volume of the foil studied at ε = 50%. The fragments being formed in ferrite plates are separated by low-angle boundaries. The average size of the fragmented ferrite decreases from 240 nm at ε = 15% to 200 nm at ε = 50%. Concurrently with the ferrite fragmentation, fragments of cementite are also observed. It is found that the sizes of the cementite fragments are in a range of 15 to 20 nm and depend weakly on the degree of sample deformation. The cementite fragmentation is caused by deformation-induced carbon dissolution and dislocation-induced fracture. The carbon atoms diffuse from cementite crystal to dislocations, which move through an interplanar space to form particles of tertiary cementite at nanoscale (2–4 nm). It is found that the increase in the degree of deformation is accompanied by a decrease in the scalar and an excess dislocation density. A physical interpretation of the observations has been given. Full article
(This article belongs to the Special Issue Deformation of Metals and Alloys: Theory, Simulations and Experiments)
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11 pages, 3730 KiB  
Article
Selective Separation Recovery of Copper and Arsenic from the Leaching Solution of Copper Soot
by Zhizhao Yang, Yongbing Zhang, Hepeng Zhou, Xianping Luo, Xuekun Tang and Zishuai Liu
Metals 2022, 12(11), 1983; https://doi.org/10.3390/met12111983 - 20 Nov 2022
Cited by 3 | Viewed by 1518
Abstract
Through the main chemical reaction of metal ions and S2−, a new type of sulfide precipitant was first prepared and used to realize the selective separation recovery of copper and arsenic from the leaching solution of copper soot. It is proven [...] Read more.
Through the main chemical reaction of metal ions and S2−, a new type of sulfide precipitant was first prepared and used to realize the selective separation recovery of copper and arsenic from the leaching solution of copper soot. It is proven by experimental results that the prepared sulfide precipitant could realize the efficient separation recovery of copper and arsenic. Indeed, the copper sulfide slag with Cu grade of about 47% and arsenic trisulfide slag with As operation recovery of about 98% could be obtained. The results of chemical reaction energy calculation analysis and SEM images analysis illustrate that the selective separation recovery of copper and arsenic mainly depended on the chemical reactions of sulfide precipitation. The ions of S2− and HS produced by the prepared sulfide precipitant could react with Cu2+ and arsenic components to form CuS and As2S, respectively, in the copper and arsenic recovery procedure. In addition, the smaller solubility of CuS and the lower rate of S2− engendered by the sulfide precipitant were key to achieving the efficient separation and recovery of copper and arsenic. Full article
(This article belongs to the Topic Green Low-Carbon Technology for Metalliferous Minerals)
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18 pages, 6550 KiB  
Article
Application of Optimizing Slab Corner Shapes to Reduce Edge Seam Defect on Heavy Plates
by Minglin Wang, Hui Zhang, Wenbo Zhao, Heping Liu and Xuebing Wang
Metals 2022, 12(11), 1984; https://doi.org/10.3390/met12111984 - 19 Nov 2022
Viewed by 1756
Abstract
The edge seam defect is a common defect in hot rolling heavy plates. It can be improved by optimizing the corner shapes of slabs. Based on a numerical analysis of the effects of the slab corner shape on the temperature distribution after the [...] Read more.
The edge seam defect is a common defect in hot rolling heavy plates. It can be improved by optimizing the corner shapes of slabs. Based on a numerical analysis of the effects of the slab corner shape on the temperature distribution after the slab’s exit from the heating furnace, three rolling methods are proposed for controlling the two-chamfered slab corner shape. The stress and deformation of the corner of the slab during the two-chamfered rolling process are investigated using a numerical simulation. The results show that a two-chamfered shape slab has the smallest temperature drop during the cooling process, and the slab corner can maintain higher temperature and uniformity, which is beneficial for controlling the deformation during the rolling process. Among the three kinds of two-chamfered rolling methods, frontal rolling using a two-roller has the smallest rolling force and rolling resistance to the casting machine, followed by horizontal rolling and then vertical rolling, which has the largest. The favorable slab corner in a two-chamfered shape can be obtained by frontal rolling using a two-roller. Industrial trials confirm that an edge seam defect rate of less than 5% in heavy plates can be achieved under the condition of a large broadside ratio. Full article
(This article belongs to the Special Issue Computational Methods in Metallic Materials Manufacturing Processes)
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18 pages, 87388 KiB  
Article
Microstructure Evolution Behavior of Spray-Deposited 7055 Aluminum Alloy during Hot Deformation
by Di Feng, Rui Xu, Jichen Li, Wenjie Huang, Jingtao Wang, Ying Liu, Linxiang Zhao, Chengbo Li and Hao Zhang
Metals 2022, 12(11), 1982; https://doi.org/10.3390/met12111982 - 19 Nov 2022
Cited by 7 | Viewed by 1617
Abstract
The evolution behaviors of the second phase, substructure and grain of the spray-deposited 7055 aluminum alloy during hot compression at 300~470 °C were studied by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results show that the AlZnMgCu [...] Read more.
The evolution behaviors of the second phase, substructure and grain of the spray-deposited 7055 aluminum alloy during hot compression at 300~470 °C were studied by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results show that the AlZnMgCu phase resulting from the deposition process dissolves gradually with the increase in deformation temperature, but the Al7Cu2Fe phase remains unchanged. The plastic instability of the spray-deposited 7055 aluminum alloy occurs at 470 °C with a 1~5 s−1 strain rate range. Partial dynamic recrystallization (PDRX) adjacent to the original high angle grain boundaries (HAGBs) not only occurs at 300~400 °C with the low strain rates ranging from 0.001 to 0.1 s−1 but also at 450 °C with a high strain rate of 5 s−1. Continuous dynamic recrystallization (CDRX) appears at 450 °C with a low strain rate of 0.001 s−1. The primary nucleation mechanism of PDRX includes the rotation of the subgrain adjacent to the original HAGBs and the subgrain boundary migration. The homogeneous misorientation increase in subgrains is the crucial nucleation mechanism of CDRX. At 300~400 °C, the residual coarse particle stimulated (PSN) nucleation can also be observed. Full article
(This article belongs to the Special Issue Aluminum Alloys and Aluminum-Based Matrix Composites)
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16 pages, 6898 KiB  
Article
Impact Abrasive Wear of Cr/W-DLC/DLC Multilayer Films at Various Temperatures
by Wen Zhong, Haoyu Wang, Lei Ma and Changhua Zhang
Metals 2022, 12(11), 1981; https://doi.org/10.3390/met12111981 - 19 Nov 2022
Cited by 4 | Viewed by 1486
Abstract
Diamond-like carbon (DLC) films are widely used in key parts of nuclear reactors as a protective coating. A study on the abrasive wear property of Cr/W-DLC/DLC multilayer films was performed at various temperatures. Results show that the mechanism of impact wear under no [...] Read more.
Diamond-like carbon (DLC) films are widely used in key parts of nuclear reactors as a protective coating. A study on the abrasive wear property of Cr/W-DLC/DLC multilayer films was performed at various temperatures. Results show that the mechanism of impact wear under no sand condition is mainly plastic deformation. The multilayer film still has excellent impact wear resistance and favorable adhesion with 308L stainless steel substrate at elevated temperatures under no sand conditions. Sand particles destroy the surface of the multilayer film due to the effect of cutting and ploughing, leading to a nine-fold increase in the wear area. The impact wear mechanism changes into abrasive wear with sand addition. Oxidation wear exists on 308L stainless steel substrate material due to the removal of the multilayer film at high temperatures. More energy is absorbed for plastic deformation and material removal under sand conditions, resulting in lower rebound velocity and peak contact force than under no sand conditions. The temperature leads to the softening of the substrate; thus, the specimens become more prone to plastic deformation and material removal. Full article
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18 pages, 13341 KiB  
Article
Atmospheric Corrosion Evolution of Carbon Steel AISI 1020 along a Longitude Transect in the Atacama Desert
by Luis Cáceres, Alvaro Soliz and Felipe Galleguillos
Metals 2022, 12(11), 1980; https://doi.org/10.3390/met12111980 - 19 Nov 2022
Cited by 1 | Viewed by 1745
Abstract
Carbon steel AISI 1020 was exposed to environmental conditions along a transect of the Atacama Desert to gather experimental evidence to identify the local atmospheric mechanism that triggers corrosion through a buildup of water layer formation on the metal surface in addition to [...] Read more.
Carbon steel AISI 1020 was exposed to environmental conditions along a transect of the Atacama Desert to gather experimental evidence to identify the local atmospheric mechanism that triggers corrosion through a buildup of water layer formation on the metal surface in addition to corrosion evolution. Coupons initially left in selected sites were periodically collected to determine weight loss and surface attributes by scanning electron microscopy and X-ray diffraction. In addition, meteorological conditions were measured in addition to a fog water collector in one site. During the study period, the predominant conditions were the absence of rain, clear skies, and large daily oscillations in temperature and relative humidity. The evidence indicates a water film formation on a metal surface either from a vertical water flux as fog water droplets and/or by the dew water harvesting mechanism. The uptakes of oxygen and chlorides during the corrosion process were highest in the coastal site P0 and gradually decreased with the increasing distance from the coast. This is attributed to both humidity and saline marine fog intrusion from the coast. The oxide layer evolved to form a compact layer with main constituents of lepidocrocite, goethite, and lesser amounts of akageneite. The corrosion depth can be modelled by a simple power function d=AtB with B < 1, indicating a deceleration process. Full article
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15 pages, 6747 KiB  
Article
Structural Optimization, Fabrication, and Corrosion Behaviors of Biodegradable Mg-Nd-Zn-Zr Alloy Hemostatic Clip
by Lin Mao, Xin Zheng, Yongji Tian, Yiling Shi, Xiaochen Zhang and Chengli Song
Metals 2022, 12(11), 1979; https://doi.org/10.3390/met12111979 - 19 Nov 2022
Cited by 2 | Viewed by 1511
Abstract
In this study, the process of ligating blood vessels via biodegradable Mg alloy hemostatic clips with toothless, transverse teeth, and embedded teeth was simulated through finite element analysis (FEA). The results showed that the transverse tooth clip caused the minimum stress (0.81489 MPa) [...] Read more.
In this study, the process of ligating blood vessels via biodegradable Mg alloy hemostatic clips with toothless, transverse teeth, and embedded teeth was simulated through finite element analysis (FEA). The results showed that the transverse tooth clip caused the minimum stress (0.81489 MPa) to blood vessels. Furthermore, the effects of clips with transverse teeth of different parameters, including lower tooth length, tooth height, and tooth pitch, on clamped blood vessels were studied. The numerical simulation results showed that the three optimal parameters for clips with transverse teeth were 0.2, 0.1, and 0.1 mm, respectively. Then, the optimally designed clip based on the Mg–Nd–Zn–Zr alloy was manufactured and evaluated using immersion tests. Results from the corrosion behavior study showed that closed clips (0.118 ± 0.041 mg·cm−2·day−1) corroded slightly faster than open clips (0.094 ± 0.041 mg·cm−2·day−1). Moreover, micromorphological observations showed that no cracks appeared on the closed clips, indicating that the Mg alloy had excellent performance and avoided stress corrosion cracking (SCC). Thus, the new type of Mg alloy clip kept good blood vessel closure during FEA and exhibited no corrosion cracking during the degradation process, making it a promising candidate for applications with biodegradable hemostatic clips. Full article
(This article belongs to the Section Biobased and Biodegradable Metals)
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15 pages, 9698 KiB  
Article
Effects of Simulated PWHT on the Microstructure and Mechanical Properties of 2.25Cr1Mo0.25V Steel for a Hydrogenation Reactor
by Yanmei Li, Yonghao Cui, Jimou Zhang, Minghui Song and Chen Xu
Metals 2022, 12(11), 1978; https://doi.org/10.3390/met12111978 - 19 Nov 2022
Cited by 1 | Viewed by 2604
Abstract
The effect of post-welding heat treatment (PWHT) on the microstructure and mechanical properties of large-thickness 2.25Cr1Mo0.25V steel was investigated through simulated post-welding heat treatment (SPWHT). The results showed that an increase in the SPWHT time decreased the toughness, hardness, and strength of the [...] Read more.
The effect of post-welding heat treatment (PWHT) on the microstructure and mechanical properties of large-thickness 2.25Cr1Mo0.25V steel was investigated through simulated post-welding heat treatment (SPWHT). The results showed that an increase in the SPWHT time decreased the toughness, hardness, and strength of the steel. After Min.SPWHT, the high-temperature tensile strength decreased more significantly, and the damage of Min.SPWHT to the high-temperature tensile strength reached approximately 80% of the Max.SPWHT. The microstructure of the tested steel before and after SPWHT consisted of granular bainite and lath bainite. After SPWHT, intergranular carbides were precipitated as coarsened carbides, carbide clusters, and chains of carbides; alloy element segregation occurred, and the segregation of Mo was the most serious, followed by Cr, and V. The precipitation behavior of the carbides and the increase in the effective grain size caused by the widening of the bainite–ferrite lath worked together and resulted in the decline of the impact toughness; the reduction in the solid solution and precipitation strengthening effects were the main factors in the strength reduction of the tested steel. In the high-temperature tensile tests, defects first appeared around the coarse carbides and carbide clusters. Controlling the size of the intergranular large-size carbides and the degree of cluster precipitation in the NT state structure may be a means of obtaining higher strength of the base metal subjected to PWHT. Full article
(This article belongs to the Special Issue Advanced Technology in Microalloyed Steels)
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14 pages, 3744 KiB  
Article
Evaluation Method and Application of Cold Rolled Strip Flatness Quality Based on Multi-Objective Decision-Making
by Qiuna Wang, Jingdong Li, Xiaochen Wang, Quan Yang and Zedong Wu
Metals 2022, 12(11), 1977; https://doi.org/10.3390/met12111977 - 19 Nov 2022
Cited by 4 | Viewed by 1445
Abstract
Flatness is a vital quality index that determines the dimensional accuracy of the cold-rolled strip. This paper designs a local shape wave extraction algorithm and a fuzzy classification algorithm for overall flatness defect classification based on cosine distance. By introducing the small displacement [...] Read more.
Flatness is a vital quality index that determines the dimensional accuracy of the cold-rolled strip. This paper designs a local shape wave extraction algorithm and a fuzzy classification algorithm for overall flatness defect classification based on cosine distance. By introducing the small displacement buckling theory of thin plates, the plate stress buckling model of overall and local shape waves is studied, and the critical buckling elongation difference of the overall shape and the local shape under the given conditions are obtained. Finally, using the multi-objective decision-making evaluation method, a comprehensive evaluation model of the flatness quality is established. The model is applied to the actual cold rolling production. The on-site flatness data are used to verify the flatness quality determination model both locally and overall. The results show that the model can accurately identify the local and overall flatness defects of cold-rolled strips, realizes the accurate identification and evaluation of the cold-rolled flatness quality, and provides strong support for the optimization of rolling process parameters and the improvement of the quality of thin strip products. Full article
(This article belongs to the Section Computation and Simulation on Metals)
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18 pages, 1731 KiB  
Article
Optimization of Process Parameters for Powder Bed Fusion Additive Manufacturing Using a Linear Programming Method: A Conceptual Framework
by Alexander Khaimovich, Andrey Balyakin, Maxim Oleynik, Artem Meshkov and Vitaly Smelov
Metals 2022, 12(11), 1976; https://doi.org/10.3390/met12111976 - 19 Nov 2022
Cited by 4 | Viewed by 2283
Abstract
At present, the selection of optimal technological parameters for laser powder bed fusion (LPBF) is determined by the requirements of the fusion process. The main parameters that are commonly varied include laser power (P), scanning speed (v), hatch spacing [...] Read more.
At present, the selection of optimal technological parameters for laser powder bed fusion (LPBF) is determined by the requirements of the fusion process. The main parameters that are commonly varied include laser power (P), scanning speed (v), hatch spacing (h), and layer thickness (t). The productivity of the LPBF process (the increment in the fused volume of the material) is equal to the product of the last three parameters, and the mechanical properties are largely determined by the volumetric fusion energy density, which is equal to the ratio of laser power to productivity. While ensuring maximum process productivity, it is possible to obtain acceptable quality characteristics—mechanical properties, surface roughness, etc.—for a certain range of LPBF technological parameters. In these cases, several quality characteristics act as constraints on the optimization process, and productivity and the key quality characteristics become components of the objective function. Therefore, this article proposes a formalized representation of the optimization problem for the LPBF process, including the derivation of the objective function with the constraint matrix, and provides a solution to the problem using the linear programming (LP) method. The advantages of the proposed method include the guaranteed convergence of the solution with an unlimited number of constraints; the disadvantage concerns the adequacy of the solution, which is limited by a relatively narrow range of parameter changes. The proposed method was tested in determining the optimal LPBF parameters for an HN58MBYu powder LP model that included 13 constraints and an objective function with two target parameters. The obtained results made it possible to increase the productivity by 15% relative to the basic technological parameters. Full article
(This article belongs to the Section Additive Manufacturing)
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10 pages, 3541 KiB  
Article
Effects of Vacancy Defects on Electrical and Optical Properties of ZnO/WSe2 Heterostructure: First-Principles Study
by Xi Yong, Ao Wang, Lichuan Deng, Xiaolong Zhou and Jintao Li
Metals 2022, 12(11), 1975; https://doi.org/10.3390/met12111975 - 18 Nov 2022
Cited by 1 | Viewed by 1374
Abstract
In this work, based on the first principles calculation of density functional theory (DFT), we studied the band structure changes of monolayer ZnO and ZnO/WSe2 before and after vacancy generation, and systematically studied the vacancy formation energy, band structure, density of states, [...] Read more.
In this work, based on the first principles calculation of density functional theory (DFT), we studied the band structure changes of monolayer ZnO and ZnO/WSe2 before and after vacancy generation, and systematically studied the vacancy formation energy, band structure, density of states, electronic density difference and optical properties of ZnO/WSe2 heterostructure before and after vacancy generation. The results show that the band structures of ZnO, WSe2, and ZnO/WSe2 heterostructure are changed after the formation of Zn, O, W, and Se vacancies. The bandgap of the ZnO/WSe2 heterostructure can be effectively controlled, the transition from direct to indirect bandgap semiconductor will occur, and the heterostructure will show metallic properties. The optical properties of heterostructure have also changed significantly, and the absorption capacity of heterostructure to infrared light has been greatly increased with red shift and blue shift respectively. The generation of vacancy changes the electrical and optical properties of ZnO/WSe2 heterostructure, which provides a feasible strategy for adjusting the photoelectric properties of two-dimensional optoelectronic nano devices and has good potential and broad application prospects. Full article
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12 pages, 3536 KiB  
Article
Tin Removal from Tin-Bearing Iron Concentrate with a Roasting in an Atmosphere of SO2 and CO
by Lei Li, Zhipeng Xu and Shiding Wang
Metals 2022, 12(11), 1974; https://doi.org/10.3390/met12111974 - 18 Nov 2022
Cited by 1 | Viewed by 1125
Abstract
The tin could be volatilized and removed effectively from the tin-bearing iron concentrate while roasted in an atmosphere of SO2 and CO. The reduction of SO2 by CO occurred in preference to the SnO2 and Fe3O4, [...] Read more.
The tin could be volatilized and removed effectively from the tin-bearing iron concentrate while roasted in an atmosphere of SO2 and CO. The reduction of SO2 by CO occurred in preference to the SnO2 and Fe3O4, and the generated S2 could sulfurize the SnO2 to an evaporable SnS, which resulted in the tin volatilization. However, the Fe3O4 could be sulfurized simultaneously, and a phase of iron sulfide was formed, retaining in the roasted iron concentrate. It decreased the quality of the iron concentrate. In addition, the formation of Sn-Fe alloy was accelerated as the roasting temperature exceeded 1100 °C, which decreased the Sn removal ratio. An appropriate SO2 partial pressure and roasting temperature should be controlled. Under the condition of the roasting temperature of 1050 °C, SO2 partial pressure of 0.003, CO partial pressure of 0.85, and residence time of 60 min, the tin content in the roasted iron concentrate was decreased to 0.032 wt.% and the sulfur residual content was only 0.062 wt.%, which meets the standard of iron concentrate for BF ironmaking. Full article
(This article belongs to the Special Issue Metal Recovery and Separation from Wastes)
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13 pages, 15034 KiB  
Article
Effect of Solution Heat Treatment on the Porosity Growth of Nickel-Based P/M Superalloys
by Hengyong Bu, Lu Chen and Yonghua Duan
Metals 2022, 12(11), 1973; https://doi.org/10.3390/met12111973 - 18 Nov 2022
Cited by 5 | Viewed by 1568
Abstract
Thermal-induced porosity (TIP) is one of the major defects in powder metallurgy (P/M) superalloys, and it seriously affects the performance of P/M superalloys. The effects of solution heat treatment on the growth of the TIP of the nickel-based P/M superalloy FGH97 were investigated. [...] Read more.
Thermal-induced porosity (TIP) is one of the major defects in powder metallurgy (P/M) superalloys, and it seriously affects the performance of P/M superalloys. The effects of solution heat treatment on the growth of the TIP of the nickel-based P/M superalloy FGH97 were investigated. A series of solution heat treatment tests were carried out at holding temperatures ranging from 1150 to 1200 °C, with holding times ranging from 0.5 to 8 h. The results showed that the holding time, temperature, and the initial volume of porosity are the primary factors influencing porosity growth, and the volume fraction of TIPs increases by increasing the temperature or extending the holding time. The porosity growth models were constructed based on the porosity statistics combined with a nonlinear fitting method. To evaluate the accuracy of the proposed models, the correlation coefficient (R) and average absolute relative error (AARE) were calculated between the predicted and experimental values. The unbiased AARE values were 2.06% and 3.99% for the average value of TIP and the worst value of TIP, respectively, which imply that the proposed porosity growth models have greater accuracy and can be used to illustrate TIP behavior in solution heat treatment. Full article
(This article belongs to the Special Issue Heat Resistant Steels and Alloys)
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15 pages, 6059 KiB  
Article
Microstructure Refinement by a Combination of Heat Treatment and Thixoforming Process Followed by Severe Plastic Deformation and Their Effects on Al-Si Alloy Hardness
by Mohamed Abdelgawad Gebril, Mohd Zaidi Omar, Intan Fadhlina Mohamed, Norinsan Kamil Othman and Osama M. Irfan
Metals 2022, 12(11), 1972; https://doi.org/10.3390/met12111972 - 18 Nov 2022
Cited by 4 | Viewed by 1226
Abstract
This study fabricated a thixoformed Al-7% Si alloy using the cooling slope technique and subjected it to heat treatment before processing with severe plastic deformation to determine the effect of this combination method on the microstructure refinement and hardness of Al-Si alloys (300 [...] Read more.
This study fabricated a thixoformed Al-7% Si alloy using the cooling slope technique and subjected it to heat treatment before processing with severe plastic deformation to determine the effect of this combination method on the microstructure refinement and hardness of Al-Si alloys (300 Series). Each as-cast and thixoformed Al-Si alloy sample was subjected to equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) individually at room temperature before and after heat treatment. ECAP was conducted in a mould with a 120° channel angle via route A, and HPT was applied with 0.75 and 5 turns. The heat-treated thixoformed Al-Si alloy subjected to the HPT process had an ultra-fine grain microstructure and showed a fine and homogeneous redistribution of the eutectic phase in the Al matrix. For the as-cast alloy, the hardness of the heat-treated thixoformed Al-7% Si alloy increased from 63 HV to 124 and 215 Hv after two ECAP passes and five turns of HPT due to the reduced and redistributed eutectic phase in the Al matrix. Subjecting the Al-7% Si alloy to a combination of semisolid and heat treatment processes before subjecting it to severe plastic deformation resulted in microstructural refinement and improved the hardness of the Al-Si alloy. The results indicate that HPT is a more effective method than ECAP for increasing the hardness of the thixoformed Al-Si alloy due to microstructure refinement. Full article
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11 pages, 4611 KiB  
Article
Comparison of Submillimeter Spot Ablation of Copper and Nickel by Multipulse Picosecond and Femtosecond Laser
by Mingyu Li, Jifei Ye, Lan Li, Bangdeng Du, Ying Wang, Heyan Gao and Chenghao Yu
Metals 2022, 12(11), 1971; https://doi.org/10.3390/met12111971 - 18 Nov 2022
Viewed by 1276
Abstract
The current transmission and reflection laser ablation micropropulsion modes have the problem of a complex working medium supply system in engineering. Therefore, we propose large-spot laser ablation with a one-dimensional supply mode. In order to verify this ablation mode, a multipulse ablation experiment [...] Read more.
The current transmission and reflection laser ablation micropropulsion modes have the problem of a complex working medium supply system in engineering. Therefore, we propose large-spot laser ablation with a one-dimensional supply mode. In order to verify this ablation mode, a multipulse ablation experiment of submillimeter-scale light spots was carried out on the surface of pretreated copper and nickel under the atmosphere using an ultrafast laser with a pulse width of 290 fs and 10 ps. The results show that femtosecond laser multipulse ablation (FLMA) leads to the grain refinement of copper, the crater quality of the two metals under FLMA is better, and picosecond laser multipulse ablation (PLMA) causes the crater of nickel to form a dense remelting bulge that affects laser absorption; both metals have obvious heat-affected zones after FLMA and PLMA, the heat-affected zones of nickel are 5–10% larger than those of copper, and the ablation depth of copper is deeper. Under the same conditions, the ablation mass of copper is smaller than that of nickel, and the specific impulse performance of laser ablation micropropulsion is better. Full article
(This article belongs to the Special Issue Laser Materials Processing Technology)
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11 pages, 1835 KiB  
Article
Microstructure, Mechanical Properties, and Fish-Scaling Resistance of a Ti-Nb Microalloyed Hot-Rolled Enamel Steel
by Yi Zhang, Bo Yu, Jian Zhang, Yu Du, Xiaonan Wang, Hongyan Wu, Xiuhua Gao and Linxiu Du
Metals 2022, 12(11), 1970; https://doi.org/10.3390/met12111970 - 18 Nov 2022
Cited by 1 | Viewed by 1388
Abstract
Currently, the fish-scaling resistance of most hot-rolled enamel steels is improved by adding Ti to form fine TiC carbides as hydrogen traps. Given that the hydrogen capture capacity of NbC is higher than that of TiC, the manufacture of hot-rolled enamel steels via [...] Read more.
Currently, the fish-scaling resistance of most hot-rolled enamel steels is improved by adding Ti to form fine TiC carbides as hydrogen traps. Given that the hydrogen capture capacity of NbC is higher than that of TiC, the manufacture of hot-rolled enamel steels via Ti-Nb microalloying has a promising future. In the present study, a Ti-Nb microalloyed hot-rolled enamel steel was developed, and its microstructure, mechanical properties, and fish-scaling resistance were studied by optical microscopy, transmission electron microscopy, tensile test, and hydrogen permeation test. The results show that the microstructure of hot-rolled experimental steel is composed of ferrite and fine carbides, with a large number of fine precipitates uniformly distributed in the ferrite grains. After the first and second enamel firings, the average sizes of ferrite grain and precipitates gradually increase, the yield strength decreases from 711 ± 9 MPa to 471 ± 17 MPa and 409 ± 8 MPa, the tensile strength decreases from 761 ± 7 MPa to 524 ± 15 MPa and 490 ± 12 MPa, and the elongation increases from 21.0 ± 2.8% to 27.8 ± 1.8% and 33.9 ± 1.1%. The hydrogen permeation value (TH value) decreases from 35.9 min/mm2 to 6.8 min/mm2 and 3.9 min/mm2 after the first and second enamel firings. That is, the fish-scaling resistance of hot-rolled experimental steel is significantly reduced after enamel firing, which is caused by the coarsening of precipitates, resulting in a significant reduction in the density of irreversible hydrogen traps (from 1.21 × 1025 cm−3 to 6.50 × 1023 cm−3 and 4.27 × 1023 cm−3). A large amount of semi-coherent precipitates is the key to obtaining the good fish-scaling resistance of hot-rolled enamel steel. Full article
(This article belongs to the Special Issue Advanced Technology in Microalloyed Steels)
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11 pages, 2273 KiB  
Article
Kinetics of Bainite Transformation in Multiphase High Carbon Low-Silicon Steel with and without Pre-Existing Martensite
by Zeinab Babasafari, Alexey V. Pan, Farshid Pahlevani, Suk Chun Moon, Madeleine Du Toit and Rian Dippenaar
Metals 2022, 12(11), 1969; https://doi.org/10.3390/met12111969 - 18 Nov 2022
Cited by 2 | Viewed by 1703
Abstract
In the present study, the isothermal decomposition of austenite to bainite in 1.0 wt% carbon, 0.21% silicon steel during the partitioning step of a quenching and partitioning (Q&P) heat treatment has been investigated in a dilatometer in the temperature range of 200 to [...] Read more.
In the present study, the isothermal decomposition of austenite to bainite in 1.0 wt% carbon, 0.21% silicon steel during the partitioning step of a quenching and partitioning (Q&P) heat treatment has been investigated in a dilatometer in the temperature range of 200 to 350 °C and compared to conventional austempering heat treatment. The bainite transformation was shortened by about 75% in the presence of pre-existing martensite (QP). The kinetics of bainite transformation is described by the well-known Avrami equation. The calculated parameter ‘n’ in the Avrami equation shows that bainite forms in the absence of pre-existing martensite (TT) at a constant nucleate rate, while in the presence of pre-existing martensite, nucleation is interface controlled. The overall bainite transformation activation energy, calculated by the Avrami equation, ranges from 64 to 110 kJ/mol. The outcomes of this investigation provide guidelines for the development of multiphase microstructures, including pre-existing martensite and bainite in high-carbon low-silicon steel, within an industrially acceptable time scale and mechanical performance. Full article
(This article belongs to the Topic Energy-Saving and Emission Reduction in Metallurgy)
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22 pages, 13796 KiB  
Article
Effects of Build Orientations on Microstructure Evolution, Porosity Formation, and Mechanical Performance of Selective Laser Melted 17-4 PH Stainless Steel
by Mohammad Azlan Aripin, Zainuddin Sajuri, Nashrah Hani Jamadon, Amir Hossein Baghdadi, Junaidi Syarif, Intan Fadhlina Mohamed and Ahmad Muhammad Aziz
Metals 2022, 12(11), 1968; https://doi.org/10.3390/met12111968 - 17 Nov 2022
Cited by 10 | Viewed by 2283
Abstract
In this study, the effect of phase, microstructure, and porosity in Selective Laser Melting (SLM) on hardness, tensile, and fracture behavior of 17-4 PH was investigated. The increasing interest in SLM in producing complex parts has encouraged the industry to produce performance parts, [...] Read more.
In this study, the effect of phase, microstructure, and porosity in Selective Laser Melting (SLM) on hardness, tensile, and fracture behavior of 17-4 PH was investigated. The increasing interest in SLM in producing complex parts has encouraged the industry to produce performance parts, such as martensitic 17-4 PH stainless steel. However, the microstructure and mechanical behavior of SLM 17-4PH is not fully understood by researchers. Understanding the microstructure profile is complex because it is driven by thermal history and porosity. Both elements vary, based on the build directions, further hindering researchers from fully understanding the mechanical properties. To fabricate specimens in three different building orientations (0°, 45°, and 90°), 17-4 powder was used. Two phases, namely, austenite and martensite, with 90° build direction, retained more austenite, due to the reheating process on a smaller base area. The optical microstructure revealed several elements that were distinct for SLM processing, including circular, columnar lath, wave melt pool, and porosity. Columnar lath was found to grow continuously across different melt pools. Hardness was found to be higher for 0° than for 90°, due to higher martensite content. Tensile strength was highest for 0°, at 958 MPa, higher than at 45° and 90° at 743 and 614 MPa, respectively. Porosity analysis validated that 90° had all three types of porosities and, specifically, the crescent type, which held un-melted powders. All types of porosities were found in fractography analysis. Full article
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10 pages, 2389 KiB  
Article
Effect of Secondary Phases on Multi-Step Phase Transitions and Magnetocaloric Properties in MnFe-Based Alloys
by A-Young Lee, Min-Ha Lee, Song-Yi Kim, JunHee Han, Ki-Hoon Kang and Jong-Woo Kim
Metals 2022, 12(11), 1967; https://doi.org/10.3390/met12111967 - 17 Nov 2022
Viewed by 1410
Abstract
This study investigated the effect of the secondary phases on multi-step phase transitions and the magnetocaloric properties depending on the Ge content in the MnFeCoPSiGe alloys. Two-step phase transitions were observed by the variations of the Fe2P-type hexagonal structure (first-order) and [...] Read more.
This study investigated the effect of the secondary phases on multi-step phase transitions and the magnetocaloric properties depending on the Ge content in the MnFeCoPSiGe alloys. Two-step phase transitions were observed by the variations of the Fe2P-type hexagonal structure (first-order) and secondary phases (second-order). The Curie temperature alters with non-linear behavior consistent with change of the lattice parameters. In addition, the magnetic entropy change decreased with the increase of the Ge content and, subsequently, fractions of the secondary phases. However, the morphological variation of microstructure, distributed as a circular-type shape of the Fe2P-type hexagonal structure in the Ge-rich matrix, increased the magnetic entropy change. Therefore, the addition of Ge enables the control of the Curie temperature to be applicable for high temperature operating devices. The control of the secondary phases and morphology of the microstructure are crucial to improve the phase transition and magnetic entropy change. Full article
(This article belongs to the Special Issue Phase Transition and Magnetic Effect of Magnetic Alloy)
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