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Metals, Volume 12, Issue 4 (April 2022) – 168 articles

Cover Story (view full-size image): Core-shell magnetic nanoparticles are used in a broad spectrum of applications. Their hyperthermia and drug delivery usage have escalated since using shell materials has proved beneficial. The shell protects the magnetic core from oxidation and provides biocompatibility for many materials. Nevertheless, their synthesis can be quite challenging as it involves several steps and parallel processes. Although reviews on magnetic core-shell nanoparticles exist, there is a lack of literature that compares the size and shape of magnetic core-shell nanomaterials synthesized via various methods. Therefore, this review outlines synthetic strategies and recent advances in magnetic core-shell nanomaterials. View this paper
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13 pages, 9572 KiB  
Article
A Strategic Design Route to Find a Depleted Uranium High-Entropy Alloy with Great Strength
by Weiran Zhang, Yasong Li, Peter K. Liaw and Yong Zhang
Metals 2022, 12(4), 699; https://doi.org/10.3390/met12040699 - 18 Apr 2022
Cited by 5 | Viewed by 2190
Abstract
The empirical parameters of mixing enthalpy (ΔHmix), mixing entropy (ΔSmix), atomic radius difference (δ), valence electron concentration (VEC), etc., are used in this study to design a depleted uranium high-entropy alloy (HEA). X-ray diffraction (XRD), scanning electron [...] Read more.
The empirical parameters of mixing enthalpy (ΔHmix), mixing entropy (ΔSmix), atomic radius difference (δ), valence electron concentration (VEC), etc., are used in this study to design a depleted uranium high-entropy alloy (HEA). X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to assess the phase composition. Compression and hardness tests were conducted to select alloy constituents with outstanding mechanical properties. Based on the experimental results, the empirical criteria of HEAs are an effective means to develop depleted uranium high-entropy alloys (DUHEAs). Finally, we created UNb0.5Zr0.5Mo0.5 and UNb0.5Zr0.5Ti0.2Mo0.2 HEAs with outstanding all-round characteristics. Both alloys were composed of a single BCC structure. The hardness and strength of UNb0.5Zr0.5Mo0.5 and UNb0.5Zr0.5Ti0.2Mo0.2 were 305 HB and 1452 MPa, and 297 HB and 1157 MPa, respectively. Full article
(This article belongs to the Special Issue Amorphous and High-Entropy Alloy Coatings)
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22 pages, 7196 KiB  
Article
Analytical Model for Temperature Prediction in Milling AISI D2 with Minimum Quantity Lubrication
by Linger Cai, Yixuan Feng, Yu-Ting Lu, Yu-Fu Lin, Tsung-Pin Hung, Fu-Chuan Hsu and Steven Y. Liang
Metals 2022, 12(4), 697; https://doi.org/10.3390/met12040697 - 18 Apr 2022
Cited by 6 | Viewed by 1496
Abstract
Milling with minimum quantity lubrication (MQL) is now a commonly used machining technique in industry. The application of the MQL significantly reduces the temperature on the machined surface, while the cost of the lubricants is limited and the pollution caused by the lubricants [...] Read more.
Milling with minimum quantity lubrication (MQL) is now a commonly used machining technique in industry. The application of the MQL significantly reduces the temperature on the machined surface, while the cost of the lubricants is limited and the pollution caused by the lubricants is better controlled. However, the fast prediction of the milling temperature during the process has not been well developed. This paper proposes an analytical model for milling temperature prediction at the workpiece flank surface with MQL application. Based on the modified orthogonal cutting model and boundary layer lubrication effect, the proposed model takes in the process parameters and can generate the temperature profile at the workpiece surface within 1 min. The model is validated with experimental data in milling AISI D2 steel. With an average absolute error of 10.38%, the proposed model provides a reasonable temperature prediction compared to the experimental results. Based on the proposed model, this paper also investigates the effect of different cutting parameters on the cutting temperature. It is found that the application of the MQL decreases the temperature at the cutting zone, especially at the flank surface of the workpiece, which is due to the heat loss led by air-oil flow. Full article
(This article belongs to the Special Issue Analytical Modeling of Advanced Manufacturing Processes)
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11 pages, 9170 KiB  
Article
Weld Formation, Microstructure Evolution and Mechanical Property of Laser-Arc Hybrid Welded AZ31B Magnesium Alloy
by Sibo Wang, Chunyan Yan and Zhengjia Gu
Metals 2022, 12(4), 696; https://doi.org/10.3390/met12040696 - 18 Apr 2022
Cited by 3 | Viewed by 1670
Abstract
Laser-arc hybrid welding of AZ31B magnesium alloy was carried out in this paper, and the effects of welding parameters (laser power, welding speed, welding current) on weld formation, microstructure evolution and mechanical property were studied. The results showed that laser-arc hybrid welding can [...] Read more.
Laser-arc hybrid welding of AZ31B magnesium alloy was carried out in this paper, and the effects of welding parameters (laser power, welding speed, welding current) on weld formation, microstructure evolution and mechanical property were studied. The results showed that laser-arc hybrid welding can inhibit the undercut defect during laser welding on the one hand, and enhance the arc stability on the other hand. The penetration depth and width showed no significant relation with the total heat input, but were linear related to the laser heat input and the arc heat input, respectively. The average grain size of the equiaxed grains was closely related to the heat input. The higher the heat input was, the larger the grains. The optimized welding parameters were laser power of 3.5 kW, welding speed of 1.8 m/min and welding current of 100 A. In this case, the weld was free of undercut and pores, and the tensile strength and elongation rate reached 190 MPa and 12%, respectively. Full article
(This article belongs to the Special Issue Heat Treatment and Forming of Magnesium and Aluminum Alloys)
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11 pages, 1230 KiB  
Review
Effect of Micro-Alloyed/Alloyed Elements on Microstructure and Properties of Fe-Mn-Al-C Lightweight Steel
by Xiqiang Ren, Yungang Li, Yanfei Qi and Chenghao Wang
Metals 2022, 12(4), 695; https://doi.org/10.3390/met12040695 - 18 Apr 2022
Cited by 6 | Viewed by 2411
Abstract
In the 14th Five Year Plan, China clearly proposes to develop the automobile strategic industry, reduce the carbon emission intensity, and formulates the carbon emission peak plan by 2030. As the automobile is the most frequently used vehicle, weight reduction can achieve the [...] Read more.
In the 14th Five Year Plan, China clearly proposes to develop the automobile strategic industry, reduce the carbon emission intensity, and formulates the carbon emission peak plan by 2030. As the automobile is the most frequently used vehicle, weight reduction can achieve the purpose of energy-saving and emission reduction and help to achieve the peak of carbon emissions as soon as possible. The lightweight automobile steel is the research hotspot in the future, and the lightweight steel has attracted much attention in the automobile manufacturing industry. Fe-Mn-Al-C lightweight steel, with its high strength, good oxidation resistance at high temperatures, good fatigue performance, high elongation, and good energy absorption during a collision, etc., has attracted the attention of researchers in the field of automotive steel. It is found that the addition of micro-alloyed/alloyed elements to Fe-Mn-Al-C lightweight steel is of great significance to improve its properties. In this paper, the effects of micro-alloyed elements (Nb and V) and alloy elements (Si, Cr, and Cu) on the microstructure, properties, and κ-carbide of Fe-Mn-Al-C lightweight steel were reviewed. The main ways of improving the properties of Fe-Mn-Al-C lightweight steel by micro-alloyed/alloyed elements were summarized and the existing problems were analyzed to provide a reference for future research. Full article
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14 pages, 4139 KiB  
Article
Corrosion Behavior of Multiphase Bainitic Rail Steels
by Tanaporn Rojhirunsakool, Thammaporn Thublaor, Mohammad Hassan Shirani Bidabadi, Somrerk Chandra-ambhorn, Zhigang Yang and Guhui Gao
Metals 2022, 12(4), 694; https://doi.org/10.3390/met12040694 - 18 Apr 2022
Cited by 6 | Viewed by 2247
Abstract
Pearlitic steel experiences excessive corrosion in a hot and humid atmosphere. The multiphase bainitic/martensitic structure was developed for a better combination of strength and ductility, especially rolling contact fatigue, but little attention to corrosion has been investigated. Corrosion behaviors of multiphase steels obtained [...] Read more.
Pearlitic steel experiences excessive corrosion in a hot and humid atmosphere. The multiphase bainitic/martensitic structure was developed for a better combination of strength and ductility, especially rolling contact fatigue, but little attention to corrosion has been investigated. Corrosion behaviors of multiphase steels obtained from bainitic-austempering (BAT) and bainitic-quenching and -partitioning (BQ&P) processes were investigated via immersion and electrochemical tests in 3.5 wt.% NaCl solution. The corroded surface and rust after immersion and electrochemical tests were analyzed via electron microscopy, Fourier transform infrared spectra, and x-ray diffraction. The multiphase bainite + martensite/retained austenite island showed higher corrosion resistance than that of the pearlitic one. The acicular bainite obtained from the BQ&P process showed slightly higher corrosion resistance than the granular bainite + martensite structure obtained from the BAT process. Full article
(This article belongs to the Special Issue High Performance Bainitic Steels)
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10 pages, 3616 KiB  
Article
Cluster Hardening Effects on Twinning in Mg-Zn-Ca Alloys
by Ruixue Liu, Jie Wang, Leyun Wang, Xiaoqin Zeng and Zhaohui Jin
Metals 2022, 12(4), 693; https://doi.org/10.3390/met12040693 - 18 Apr 2022
Cited by 4 | Viewed by 1935
Abstract
Twinning is a critical deformation mode in Mg alloys. Understanding deformation twinning (DT) is essential to improving mechanical properties of Mg alloys. To address the experimentally observed conspicuous hardening effects in Mg-1.8Zn-0.2Ca alloys, interactions between the {10–12} twin boundaries (TBs) and solute clusters [...] Read more.
Twinning is a critical deformation mode in Mg alloys. Understanding deformation twinning (DT) is essential to improving mechanical properties of Mg alloys. To address the experimentally observed conspicuous hardening effects in Mg-1.8Zn-0.2Ca alloys, interactions between the {10–12} twin boundaries (TBs) and solute clusters in Mg-Zn-Ca alloys were examined via molecular dynamics (MD) simulations. We find that the Zn/Ca-containing clusters show different hindering effects on TBs and an increment in the applied shear stress of 100 MPa is required to accomplish the interaction between the boundary and the cluster with Ca content > 50 at%. The cluster hardening effects on twinning are positively correlated to the Ca content and the size of the clusters in Mg-Zn-Ca alloys. Full article
(This article belongs to the Special Issue Deformation, Fracture and Microstructure of Metallic Materials)
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18 pages, 5989 KiB  
Article
Low-Temperature Reactive Sintered Porous Mg-Al-Zn Alloy Foams
by Solomon-Oshioke Agbedor, Donghui Yang, Jianqing Chen, Lei Wang and Hong Wu
Metals 2022, 12(4), 692; https://doi.org/10.3390/met12040692 - 18 Apr 2022
Cited by 7 | Viewed by 1870
Abstract
By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn [...] Read more.
By using carbamide granules as the space holder, Mg alloy foams with interconnected pore structures were synthesized by reactive sintering of a mixture of Mg, Al and Zn powders. The effect of Zn/Al on the microstructural evolution and compressive strength of porous Mg-9Al-xZn (x = 1, 5) alloy foams was investigated. The phase diagram simulation approach was used to determine the sintering temperature. The analysis results show that the formation of binary secondary phases or intermetallic compounds is a crucial factor in achieving bonding strength for the porous Mg alloy foams. The intermetallic compounds were formed by solid-state diffusion between the metal powder elements. Mg17Al12 intermetallics was the most stable compound formed in the cell walls of porous Mg alloy foams. The addition of Zn influences the solubility and stability of the intermetallic compound. Thermodynamic calculations show that Mg17Al12 was preferentially formed in the cell walls owing to its high negative enthalpy energy. Moreover, various metastable transition phases may exist in the microstructures, especially in the porous Mg-9Al-5Zn alloy foam. The intermetallic phases act as reinforcing phases, combined with grain refinement, significantly increasing the strength of the foam. At the given relative density of 0.42, the porous Mg-9Al-5Zn alloy foam exhibits the highest yield strength of 9.0 MPa, which is 23% higher than the strength of the porous Mg-9Al-1Zn alloy foam. Full article
(This article belongs to the Special Issue Synthesis and Applications of Metallic Foams)
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16 pages, 6010 KiB  
Article
Predictive Modeling of Thermally Assisted Machining and Simulation Based on RSM after WAAM
by Hongyu Tian, Zhenyang Lu and Shujun Chen
Metals 2022, 12(4), 691; https://doi.org/10.3390/met12040691 - 18 Apr 2022
Cited by 3 | Viewed by 1711
Abstract
The WAAM (Wire Arc Additive Manufacturing) process is well-respected because of its low cost and high deposition efficiency; nevertheless, the process has the limitations of high heat input and low forming accuracy. Hybrid manufacturing processes employing both additive and subtractive processes can effectively [...] Read more.
The WAAM (Wire Arc Additive Manufacturing) process is well-respected because of its low cost and high deposition efficiency; nevertheless, the process has the limitations of high heat input and low forming accuracy. Hybrid manufacturing processes employing both additive and subtractive processes can effectively reduce shape error. The predictive modeling of surface roughness in thermally assisted machining is described in this paper on the basis of three important parameters: feed per tooth, spindle speed, and workpiece temperature. The predictive model indicates that temperature has a very significant influence on the surface quality. An experimental study on thermally assisted machining was performed to obtain the variation law of cutting surface quality with temperature in order to determine the optimal process interval of subtractive processes. Through finite element simulation of thermally assisted machining, the influence law of external main cutting force and the internal mean stress of the cutting material were determined. Full article
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10 pages, 2705 KiB  
Article
Investigations on Effects of Forming Parameters on Product Dimensions in Cold Drawing of AISI-316 Stainless Steel Rods
by Yeong-Maw Hwang, Hiu Shan Rachel Tsui and Man-Ru Lin
Metals 2022, 12(4), 690; https://doi.org/10.3390/met12040690 - 18 Apr 2022
Cited by 2 | Viewed by 1752
Abstract
Cold drawing is a commonly used metal forming technique carried out by pulling a billet through a die cavity to obtain desired dimensions. Ideally, the cross-sectional area of the drawn product should be equal to that of the die at its exit; however, [...] Read more.
Cold drawing is a commonly used metal forming technique carried out by pulling a billet through a die cavity to obtain desired dimensions. Ideally, the cross-sectional area of the drawn product should be equal to that of the die at its exit; however, the former one is always larger after drawing, in practice. In this study, cold drawing of an AISI-316 stainless steel rod is investigated through finite element analysis. The difference between the product radius and the die radius is denoted by ∆R. A series of simulations using combinations of various forming parameters, including semi-die angle, bearing ratio, reduction ratio, drawing speed and friction coefficient, are conducted to find out the dominant factors of ∆R. It is found that ∆R is mainly affected by semi-die angle, reduction ratio and friction. An empirical formula for ∆R, including various parameters, is established according to the simulation results and verified by drawing experiments as well. Using this empirical formula, the product dimensions can be predicted in advance and proper forming parameters can be chosen to decrease ∆R and improve the product quality. Full article
(This article belongs to the Special Issue Analysis and Design of Metal Forming Processes II)
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14 pages, 4763 KiB  
Article
Compressive Property and Energy Absorption Capacity of Mg-Ceramic-Ni Foamsat Various Temperatures
by Shouquan Shi, Weibo Sun, Xiaoru Zhang, Xianyong Zhu and Jiaan Liu
Metals 2022, 12(4), 689; https://doi.org/10.3390/met12040689 - 18 Apr 2022
Cited by 1 | Viewed by 1497
Abstract
Mg–Ceramic–Ni hybrid foams were fabricated via continuousdepositing micro-arc oxidation (MAO) ceramic coating and electroless Ni coating on the surface of the AZ91D foam struts. Mechanical tests from room temperature (RT) to 300 °C were carried out to evaluate the compressive properties and energy [...] Read more.
Mg–Ceramic–Ni hybrid foams were fabricated via continuousdepositing micro-arc oxidation (MAO) ceramic coating and electroless Ni coating on the surface of the AZ91D foam struts. Mechanical tests from room temperature (RT) to 300 °C were carried out to evaluate the compressive properties and energy absorption capacities of two types of foams, i.e., AZ91D alloy foams and corresponding hybrid foams. The effect of composite coatings and test temperature on the compressive property of the foams was studied. The experimental results show that the MAOand Ni coatings enhance the Mg foam struts, resulting in high compressive strength and energy absorption capacity at each testing temperature. In addition, the compressive properties are also depending on testing temperature. The different mechanical responses of the composite foams under various temperature conditions are mainly attributed to the different deformation behaviors and failure modes of the foam struts, which are confirmed by scanning electron microscopy (SEM) observation. Full article
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14 pages, 7477 KiB  
Article
High-Cycle Fatigue Behavior and Fatigue Strength Prediction of Differently Heat-Treated 35CrMo Steels
by Mengqi Yang, Chong Gao, Jianchao Pang, Shouxin Li, Dejiang Hu, Xiaowu Li and Zhefeng Zhang
Metals 2022, 12(4), 688; https://doi.org/10.3390/met12040688 - 17 Apr 2022
Cited by 13 | Viewed by 3288
Abstract
In order to obtain the optimum fatigue performance, 35CrMo steel was processed by different heat treatment procedures. The microstructure, tensile properties, fatigue properties, and fatigue cracking mechanisms were compared and analyzed. The results show that fatigue strength and yield strength slowly increase at [...] Read more.
In order to obtain the optimum fatigue performance, 35CrMo steel was processed by different heat treatment procedures. The microstructure, tensile properties, fatigue properties, and fatigue cracking mechanisms were compared and analyzed. The results show that fatigue strength and yield strength slowly increase at first and then rapidly decrease with the increase of tempering temperature, and both reach the maximum values at a tempering temperature of 200 °C. The yield strength affects the ratio of crack initiation site, fatigue strength coefficient, and fatigue strength exponent to a certain extent. Based on Basquin equation and fatigue crack initiation mechanism, a fatigue strength prediction method for 35CrMo steel was established. Full article
(This article belongs to the Special Issue Deformation, Fracture and Microstructure of Metallic Materials)
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34 pages, 5535 KiB  
Review
Additively Manufactured Porous Ti6Al4V for Bone Implants: A Review
by Naresh Koju, Suyash Niraula and Behzad Fotovvati
Metals 2022, 12(4), 687; https://doi.org/10.3390/met12040687 - 16 Apr 2022
Cited by 30 | Viewed by 6693
Abstract
Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect [...] Read more.
Ti-6Al-4V (Ti64) alloy is one of the most widely used orthopedic implant materials due to its mechanical properties, corrosion resistance, and biocompatibility nature. Porous Ti64 structures are gaining more research interest as bone implants as they can help in reducing the stress-shielding effect when compared to their solid counterpart. The literature shows that porous Ti64 implants fabricated using different additive manufacturing (AM) process routes, such as laser powder bed fusion (L-PBF) and electron beam melting (EBM) can be tailored to mimic the mechanical properties of natural bone. This review paper categorizes porous implant designs into non-gradient (uniform) and gradient (non-uniform) porous structures. Gradient porous design appears to be more promising for orthopedic applications due to its closeness towards natural bone morphology and improved mechanical properties. In addition, this paper outlines the details on bone structure and its properties, mechanical properties, fatigue behavior, multifunctional porous implant designs, current challenges, and literature gaps in the research studies on porous Ti64 bone implants. Full article
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17 pages, 16129 KiB  
Article
Surface Damage and Microstructure Evolution of Yttria Particle-Reinforced Tungsten Plate during Transient Laser Thermal Shock
by Daya Ren, Ya Xi, Jie Yan, Xiang Zan, Laima Luo and Yucheng Wu
Metals 2022, 12(4), 686; https://doi.org/10.3390/met12040686 - 16 Apr 2022
Cited by 3 | Viewed by 1782
Abstract
Tungsten and its alloys are considered to be the most nominated plasma-facing materials in fusion reactors, which will be exposed to enormously rigorous conditions such as thermal load, plasma exposure, and neutron radiation. At present, the research on the behavior of oxide particle-reinforced [...] Read more.
Tungsten and its alloys are considered to be the most nominated plasma-facing materials in fusion reactors, which will be exposed to enormously rigorous conditions such as thermal load, plasma exposure, and neutron radiation. At present, the research on the behavior of oxide particle-reinforced tungsten-based materials under long-term steady-state heat load and transient thermal shock is insufficient. The purpose of this study is to investigate the performance of yttria particle-reinforced tungsten plates prepared by the wet chemical method under heat loads by means of indirect coupling experiments. An Nd:YAG laser device is used to perform thermal shock events. The surface damage and microstructure evolution of rolled and fully recrystallized samples exposed to laser thermal shock are observed and analyzed. The cracking threshold of the rolled and fully recrystallized samples is about 0.40~0.48 GW/m2; the degree of surface damage of them aggravates with the increased laser power density. What is more, cracks or even melting damage could be observed on the surface and be accelerated by the process of recrystallization, resulting in the degradation of the ability to withstand the thermal shock of the material. Full article
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15 pages, 7004 KiB  
Article
Microstructure Evolution and Properties of β-TCP/Mg-Zn-Ca Biocomposite Processed by Hot Extrusion Combined with Multi-Pass ECAP
by Xiaohao Sun, Yue Su, Yan Huang, Minfang Chen and Debao Liu
Metals 2022, 12(4), 685; https://doi.org/10.3390/met12040685 - 16 Apr 2022
Cited by 6 | Viewed by 1566
Abstract
To further improve the comprehensive performance of Mg-based alloy, hot extrusion combined with multi-pass equal channel angular pressing (ECAP) was applied to process Mg-3 wt%Zn-0.2 wt%Ca alloy and 1 wt%β-TCP/Mg-3 wt%Zn-0.2 wt%Ca biocomposites. The microstructure evolution, mechanical properties, corrosion behavior, and cell biocompatibility [...] Read more.
To further improve the comprehensive performance of Mg-based alloy, hot extrusion combined with multi-pass equal channel angular pressing (ECAP) was applied to process Mg-3 wt%Zn-0.2 wt%Ca alloy and 1 wt%β-TCP/Mg-3 wt%Zn-0.2 wt%Ca biocomposites. The microstructure evolution, mechanical properties, corrosion behavior, and cell biocompatibility of the experimental specimens were systematically investigated. The average grain size of 13.4 ± 0.6 μm in MgZnCa alloy and 9.6 ± 0.3 μm in composites materials can be achieved by six ECAP passes. The uniaxial compressive strength (UCS) of 388.4 ± 7.3 MPa and the strain at failure of 14.3 ± 1.5% were confirmed in MgZnCa alloy, while the UCS of 405.3 ± 7.4 MPa and the strain at failure of 9.8 ± 1.9% were achieved by the addition of β-TCP after six ECAP passes. In spite of different compositions, the minimum corrosion rate of 0.895 mm·Y−1 and 1.117 mm·Y−1 can be achieved by two ECAP passes at 593 K. The cytocompatibility evaluation revealed that the experimental materials processed by six ECAP passes had no significant cytotoxicity to L929 cells, and the addition of β-TCP improved the cytocompatibility. Full article
(This article belongs to the Section Biobased and Biodegradable Metals)
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18 pages, 17412 KiB  
Article
Oxide Free Wire Arc Sprayed Coatings—An Avenue to Enhanced Adhesive Tensile Strength
by Manuel Rodriguez Diaz, Maik Szafarska, René Gustus, Kai Möhwald and Hans Jürgen Maier
Metals 2022, 12(4), 684; https://doi.org/10.3390/met12040684 - 16 Apr 2022
Cited by 9 | Viewed by 1939
Abstract
Conventionally, thermal spraying processes are almost exclusively carried out in an air atmosphere. This results in oxidation of the particles upon thermal spraying, and thus, the interfaces of the splats within the coating are oxidized as well. Hence, a full material bond strength [...] Read more.
Conventionally, thermal spraying processes are almost exclusively carried out in an air atmosphere. This results in oxidation of the particles upon thermal spraying, and thus, the interfaces of the splats within the coating are oxidized as well. Hence, a full material bond strength cannot be established. To overcome this issue, a mixture of monosilane and nitrogen was employed in the present study as the atomising and environment gas. With this approach, an oxygen partial pressure corresponding to an extreme-high vacuum was established in the environment and oxide-free coatings could be realized. It is shown that the oxide-free particles have an improved substrate wetting behaviour, which drastically increases the adhesive tensile strength of the wire arc sprayed copper coatings. Moreover, the altered deposition conditions also led to a significant reduction of the coating porosity. Full article
(This article belongs to the Special Issue Advances in Metal-Based Thermal Spray Coatings)
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23 pages, 9867 KiB  
Article
Electrochemical Behavior and Passive Film Properties of Hastelloy C22 Alloy, Laser-Cladding C22 Coating, and Ti–6Al–4V Alloy in Sulfuric Acid Dew-Point Corrosion Environment
by Chao Zheng, Zongde Liu, Quanbing Liu, Yao Kong, Shengyang Guo and Congcong Liu
Metals 2022, 12(4), 683; https://doi.org/10.3390/met12040683 - 15 Apr 2022
Cited by 4 | Viewed by 2258
Abstract
The electrochemical behavior and passive film properties of Hastelloy C22 alloy, laser-cladding C22 coating, and Ti–6Al–4V alloy in sulfuric acid dew-point corrosion environment were investigated through a combination of electrochemical measurements and surface analyses. The C22 alloy and laser-cladding C22 coating exhibited similar [...] Read more.
The electrochemical behavior and passive film properties of Hastelloy C22 alloy, laser-cladding C22 coating, and Ti–6Al–4V alloy in sulfuric acid dew-point corrosion environment were investigated through a combination of electrochemical measurements and surface analyses. The C22 alloy and laser-cladding C22 coating exhibited similar passivation and repassivation behavior without pitting corrosion, resulting from a similar passive film with a bilayer structure consisting of a Cr2O3-dominated compact inner layer and a porous outer layer containing oxides of Mo and hydroxides of Ni and Cr. The slightly poorer corrosion resistance and higher sensitivity to localized corrosion exhibited by the C22 coating were attributed to the microscale heterogeneity of the passive film resulting from the element segregation in the microstructure introduced by the laser-cladding process. The corrosion of the TC4 alloy performed as the preference dissolution of the β phase. Compared to the C22 alloy and C22 coating, the TC4 alloy exhibited more stable passivation behavior but poorer corrosion resistance, which is attributed to a compact but less protective single-layer passive film consisting of oxides of Ti and Al. An increase in temperature degrades passive film stability and accelerates the charge transfer process. Full article
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16 pages, 4140 KiB  
Article
Primary Study on Medium and Low Carbon Ferromanganese Production by Blowing CO2-O2 Mixtures in Converter
by Yu Han, Cheng Li and Haijuan Wang
Metals 2022, 12(4), 682; https://doi.org/10.3390/met12040682 - 15 Apr 2022
Viewed by 1655
Abstract
The production of medium- and low-carbon ferromanganese (M-LCFeMn) using the converter method has not been industrialized to date in China due to the high manganese loss and serious erosion of the furnace lining. To solve the above problems and to improve the refining [...] Read more.
The production of medium- and low-carbon ferromanganese (M-LCFeMn) using the converter method has not been industrialized to date in China due to the high manganese loss and serious erosion of the furnace lining. To solve the above problems and to improve the refining technology of M-LCFeMn, the introduction of CO2 gas into the traditional converter process is proposed. In this study, the oxidation behavior of C and Mn in various conditions was analyzed by blowing different proportions of CO2-O2 mixed gas into the high-carbon ferromanganese (HCFeMn) melt. The results showed that it is feasible to make M-CFeMn by blowing CO2-O2 mixtures, and the Mn loss can be effectively reduced during the decarburization process. It is considered that when the proportion of CO2 reaches 25%, the mixed gas has the best effect on the decarburization and manganese preservation under current experimental situation. Two hypotheses and corresponding rate formulas of decarburization kinetics by using pure oxygen are put forward, and the effect of CO2 on the kinetics of decarburization was studied according to different hypotheses. Full article
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15 pages, 9277 KiB  
Article
A Comparative Study on Mechanical and Corrosion Behaviours of α/(α + β) Mg-Li Alloys Subjected to Ultrasonic Nanocrystal Surface Modification
by Yun Zou, Shuhao Liu, Qilong Wang and Yang Li
Metals 2022, 12(4), 681; https://doi.org/10.3390/met12040681 - 15 Apr 2022
Cited by 4 | Viewed by 2005
Abstract
Ultrasonic nanocrystal surface modification (UNSM) was applied to hot-rolled Mg-Li alloys (LAE361 and LA106). The microstructure, mechanical properties, deformation mechanisms, and corrosion resistance properties of these alloys after UNSM treatment were systematically studied. Significant improvement in surface hardness and decrease in surface roughness [...] Read more.
Ultrasonic nanocrystal surface modification (UNSM) was applied to hot-rolled Mg-Li alloys (LAE361 and LA106). The microstructure, mechanical properties, deformation mechanisms, and corrosion resistance properties of these alloys after UNSM treatment were systematically studied. Significant improvement in surface hardness and decrease in surface roughness were achieved by UNSM treatment. Meanwhile, the basal texture intensity of the Mg-Li alloys reduced significantly, and several deformation twins appeared on the surface layer. The α phase of the surface layer underwent twin deformation and basal plane slip. The fibre textures in the β phase of LA106 Mg-Li alloy changed from γ and η to α and ε, which mainly resulted in the dislocation slip. More importantly, UNSM treatment exhibited enhanced strength and improved plasticity of LAE361 and LA106 Mg-Li alloys. The corrosion current density of LAE361 Mg-Li alloy reduced approximately 29.3% by UNSM treatment, while it increased the corrosion current density of LA106 Mg-Li alloy by 189.7%. These studies show that the application of UNSM to improve the corrosion resistance of duplex phases of LA106 Mg-Li alloy needs further investigation. Full article
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17 pages, 73826 KiB  
Article
Effect of Sealing Treatments on Erosion–Corrosion of a Fe-Based Amorphous Metallic Coating in 3.5 wt.% NaCl Solution with 2 wt.% Sand
by Mingming Liu, Zhengbin Wang, Hongxiang Hu, Lianmin Zhang and Yugui Zheng
Metals 2022, 12(4), 680; https://doi.org/10.3390/met12040680 - 15 Apr 2022
Cited by 4 | Viewed by 1646
Abstract
In this study, a Fe-based amorphous metallic coating (AMC) was sealed with three sealants, i.e., stearic acid, aluminum phosphate and cerium salt, respectively. Two types of electrochemical tests, namely the ex situ electrochemical impedance spectroscopy test and the in situ potentiostatic polarization test, [...] Read more.
In this study, a Fe-based amorphous metallic coating (AMC) was sealed with three sealants, i.e., stearic acid, aluminum phosphate and cerium salt, respectively. Two types of electrochemical tests, namely the ex situ electrochemical impedance spectroscopy test and the in situ potentiostatic polarization test, were conducted to evaluate the erosion–corrosion resistance of as-sprayed and as-sealed AMCs. The results show that the aluminum phosphate–sealed AMC exhibits the best erosion–corrosion resistance with the higher critical flow velocity compared with the as-sprayed AMC, which is attributed to the deep penetration of aluminum phosphate and high hardness of the sealed layer. In contrast, the sealants of stearic acid and cerium salt are easily removed by sand particle impacting, deteriorating their erosion–corrosion resistance. Full article
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13 pages, 6605 KiB  
Article
Distribution of Nonmetallic Inclusions in Slab for Tinplate
by Zhiying Mo, Zhendong Wang, Rudong Wang, Zhengzhi Zhao, Yuan Fang, Haixu Li, Yanzhao Luo, Shaojun Wang and Heng Cui
Metals 2022, 12(4), 679; https://doi.org/10.3390/met12040679 - 15 Apr 2022
Cited by 1 | Viewed by 1548
Abstract
Tinplate is widely used in food packaging and chemical packaging. Industrial production continues to reduce the thickness of tinplate steel, which puts higher requirements on the control of inclusions. In this study, compared with traditional detection methods, the Ultrasonic Detection method can analyze [...] Read more.
Tinplate is widely used in food packaging and chemical packaging. Industrial production continues to reduce the thickness of tinplate steel, which puts higher requirements on the control of inclusions. In this study, compared with traditional detection methods, the Ultrasonic Detection method can analyze the distribution of nonmetallic inclusions in larger size samples, which is closer to the actual production process. The numerical simulation model is established to analyze the flow, heat transfer and solidification behavior of molten steel. The results show: There are two nonmetallic inclusion bands in the sample at the edge of the slab, one is the inner and outer arc side of the sample, and the other is the 1/8 to 1/4 slab thickness region of the inner arc side in the sample. The inclusions in the thickness direction of the slab edge within the range of 1/8 to 1/4 are captured in areas 800 mm to 1400 mm below the meniscus. The solidification of the inner and outer arcs is not symmetrical, which leads to the asymmetrical distribution of inclusions in the inner and outer arcs. This study can provide a reference for improving the tinplate production process. Full article
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19 pages, 6442 KiB  
Article
An Approach to Assessing S960QL Steel Welded Joints Using EBW and GMAW
by Raghawendra Pratap Singh Sisodia and Marcell Gáspár
Metals 2022, 12(4), 678; https://doi.org/10.3390/met12040678 - 15 Apr 2022
Cited by 9 | Viewed by 2262
Abstract
In recent years, ultra-high-strength structural (UHSS) steel in quenched and tempered (Q+T) conditions, for example, S960QL has been found in wider application areas such as structures, cranes, and trucks due to its extraordinary material properties and acceptable weldability. The motivation of the study [...] Read more.
In recent years, ultra-high-strength structural (UHSS) steel in quenched and tempered (Q+T) conditions, for example, S960QL has been found in wider application areas such as structures, cranes, and trucks due to its extraordinary material properties and acceptable weldability. The motivation of the study is to investigate the unique capabilities of electron beam welding (EBW) compared to conventional gas metal arc welding (GMAW) for a deep, narrow weld with a small heat-affected zone (HAZ) and minimum thermal distortion of the welded joint without significantly affecting the mechanical properties. In this study, S960QL base material (BM) specimens with a thickness of 15 mm were butt-welded without filler material at a welding speed of 10 mm/s using the high-vacuum (2 × 10−4 mbar) EBW process. Microstructural characteristics were analyzed using an optical microscope (OM), a scanning electron microscope (SEM), fractography, and an electron backscatter diffraction (EBSD) analysis. The macro hardness, tensile strength, and instrumented Charpy-V impact test were performed to evaluate the mechanical properties. Further, the results of these tests of the EBW joints were compared with the GMAW joints of the same steel grade and thickness. Higher hardness is observed in the fusion zone (FZ) and the HAZ compared to the BM but under the limit of qualifying the hardness value (450 HV10) of Q+T steels according to the ISO 15614-11 specifications. The tensile strength of the EBW-welded joint (1044 MPa) reached the level of the BM as the specimens fractured in the BM. The FZ microstructure consists of fine dendritic martensite and the HAZ predominantly consists of martensite. Instrumented impact testing was performed on Charpy-V specimens at −40 °C, which showed the brittle behavior of both the FZ and HAZ but to a significantly lower extent compared to GMAW. The measured average impact toughness of the BM is 162 J and the average impact toughness value of the HAZ and FZ are 45 ± 11 J and 44 ± 20 J, respectively. Full article
(This article belongs to the Special Issue Processing of Advanced High Strength Steel (AHSS))
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17 pages, 5257 KiB  
Article
Recovery of Graphite and Cathode Active Materials from Spent Lithium-Ion Batteries by Applying Two Pretreatment Methods and Flotation Combined with a Rapid Analysis Technique
by Hao Qiu, Christoph Peschel, Martin Winter, Sascha Nowak, Johanna Köthe and Daniel Goldmann
Metals 2022, 12(4), 677; https://doi.org/10.3390/met12040677 - 15 Apr 2022
Cited by 12 | Viewed by 3765
Abstract
This work investigates the comprehensive recycling of graphite and cathode active materials (LiNi0.6Mn0.2Co0.2O2, abbreviated as NMC) from spent lithium-ion batteries via pretreatment and flotation. Specific analytical methods (SPME-GC-MS and Py-GC-MS) were utilized to identify and [...] Read more.
This work investigates the comprehensive recycling of graphite and cathode active materials (LiNi0.6Mn0.2Co0.2O2, abbreviated as NMC) from spent lithium-ion batteries via pretreatment and flotation. Specific analytical methods (SPME-GC-MS and Py-GC-MS) were utilized to identify and trace the relevant influencing factors. Two different pretreatment methods, which are Fenton oxidation and roasting, were investigated with respect to their influence on the flotation effectiveness. As a result, for NMC cathode active materials, a recovery of 90% and a maximum grade of 83% were obtained by the optimized roasting and flotation. Meanwhile, a graphite grade of 77% in the froth product was achieved, with a graphite recovery of 75%. By using SPME-GC-MS and Py-GC-MS analyses, it could be shown that, in an optimized process, an effective destruction/removal of the electrolyte and binder residues can be reached. The applied analytical tools could be integrated into the workflow, which enabled process control in terms of the pretreatment sufficiency and achievable separation in the subsequent flotation. Full article
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20 pages, 6599 KiB  
Article
Statistical Data-Driven Model for Hardness Prediction in Austempered Ductile Irons
by Nelly Abigaíl Rodríguez-Rosales, Félix Alan Montes-González, Oziel Gómez-Casas, Josué Gómez-Casas, Jesús Salvador Galindo-Valdés, Juan Carlos Ortiz-Cuellar, Jesús Fernando Martínez-Villafañe, Daniel García-Navarro and Carlos Rodrigo Muñiz-Valdez
Metals 2022, 12(4), 676; https://doi.org/10.3390/met12040676 - 15 Apr 2022
Viewed by 2342
Abstract
This research evaluates the effect of temperature and time austempering on microstructural characteristics and hardness of ductile iron, validating the results by means of a statistical method for hardness prediction. Ductile iron was subjected to austenitization at 950 °C for 120 min and [...] Read more.
This research evaluates the effect of temperature and time austempering on microstructural characteristics and hardness of ductile iron, validating the results by means of a statistical method for hardness prediction. Ductile iron was subjected to austenitization at 950 °C for 120 min and then to austempering heat treatment in a salt bath at temperatures of 290, 320, 350 and 380 °C for 30, 60, 90 and 120 min. By increasing austempering temperature, a higher content of carbon-rich austenite was obtained, and the morphology of the thin acicular ferrite needles produced at 290 °C turned completely feathery at 350 and 380 °C. A thickening of acicular ferrite needles was also observed as austempering time increased. An inversely proportional behavior of hardness values was thus obtained, which was validated through data analysis, statistical tools and a regression model taking temperature and time austempering as input variables and hardness as the output variable, which achieved a correlation among variables of about 97%. The proposal of a mathematical model for the prediction of hardness in austempered ductile iron represents a numerical approximation which validates the experimental results at 95.20%. Full article
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26 pages, 10969 KiB  
Review
A Review of the Friction Stir Welding of Dissimilar Materials between Aluminum Alloys and Copper
by Yumeng Sun, Wenbiao Gong, Jiacheng Feng, Guipeng Lu, Rui Zhu and Yupeng Li
Metals 2022, 12(4), 675; https://doi.org/10.3390/met12040675 - 14 Apr 2022
Cited by 16 | Viewed by 3813
Abstract
With the rapid development of various industries, the connection of copper and aluminum is in high demand. However, as a solid-phase connection technology, friction stir welding has a potential application prospect in the connection of copper and aluminum. This paper comprehensively summarizes the [...] Read more.
With the rapid development of various industries, the connection of copper and aluminum is in high demand. However, as a solid-phase connection technology, friction stir welding has a potential application prospect in the connection of copper and aluminum. This paper comprehensively summarizes the most recent 20 years of the literature related to the friction stir welding of copper and aluminum. The application significance of copper and aluminum connectors is introduced, and the research field of the friction stir welding of copper and aluminum is analyzed and explored from the aspects of welding technology, microstructure and mechanical properties, as well as innovations and improvements in the welding process. In view of the research status of this field, the authors put forward their views and prospects for its future, aiming to provide a basis for researchers in this field. Full article
(This article belongs to the Special Issue Advances in Friction Stir Welding Process of Metals)
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12 pages, 12669 KiB  
Article
Hot Deformation Behavior of an As-Extruded Mg-2.5Zn-4Y Alloy Containing LPSO Phases
by Guoxin Wang, Pingli Mao, Zhi Wang, Le Zhou, Feng Wang and Zheng Liu
Metals 2022, 12(4), 674; https://doi.org/10.3390/met12040674 - 14 Apr 2022
Cited by 1 | Viewed by 1363
Abstract
The hot deformation and dynamic recrystallization (DRX) characteristics of an as-extruded Mg-2.5Zn-4Y alloy containing long-period stacking ordered (LPSO) phases were investigated using a Gleeble 3500 thermal simulator at temperatures (300–400 °C) and strain rates (0.001–1 s−1). The results revealed that low flow stress [...] Read more.
The hot deformation and dynamic recrystallization (DRX) characteristics of an as-extruded Mg-2.5Zn-4Y alloy containing long-period stacking ordered (LPSO) phases were investigated using a Gleeble 3500 thermal simulator at temperatures (300–400 °C) and strain rates (0.001–1 s−1). The results revealed that low flow stress corresponded to a high temperature and a low strain rate. An increase in the temperature of deformation caused an increase in the amount of dynamic recrystallization. Additionally, as the strain rate decreased at a given deformation temperature, dislocations were less likely to cause pile-up and dynamic recrystallization was more appropriate, resulting in a lower stress value. Kink deformation was clearly minimized as the number of dynamic recrystallizations increased. The test alloy’s activation energy value was determined as 212.144 kJ/mol. Full article
(This article belongs to the Special Issue Crystal Plastic Deformation Mechanism of Metallic Materials)
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13 pages, 7376 KiB  
Article
Effect of Internal Hydrogen on the Fatigue Crack Growth Rate in the Coarse-Grain Heat-Affected Zone of a CrMo Steel
by Guillermo Álvarez, Alfredo Zafra, Francisco Javier Belzunce and Cristina Rodríguez
Metals 2022, 12(4), 673; https://doi.org/10.3390/met12040673 - 14 Apr 2022
Cited by 4 | Viewed by 2075
Abstract
The effect of internal hydrogen in the fatigue crack growth rate of the coarse grain region of a 2.25Cr1Mo steel welded joint was analyzed in this work. The microstructure of the coarse grain region was simulated by means of a heat treatment able [...] Read more.
The effect of internal hydrogen in the fatigue crack growth rate of the coarse grain region of a 2.25Cr1Mo steel welded joint was analyzed in this work. The microstructure of the coarse grain region was simulated by means of a heat treatment able to provide the same microstructure with a similar prior austenite grain size and hardness to the one in a real welded joint. The fatigue crack growth rate was measured under standard laboratory conditions using compact tensile (CT) specimens that were (i) uncharged and hydrogen pre-charged in a hydrogen pressure reactor (under 19.5 MPa and 450 °C for 21 h). The influence of fatigue frequency was assessed using frequencies of 10 Hz, 0.1 Hz, and 0.05 Hz. Additionally, two load ratios (R = 0.1 and R = 0.5) were applied to analyze their influence in the da/dN vs. ∆K curves and therefore in the fatigue crack growth rate. The embrittlement produced by the presence of internal hydrogen was clearly noticed at the beginning of the fatigue crack growth rate test (ΔK = 30 MPm), obtaining significant higher values than without hydrogen. This effect became more notorious as the test frequency decreased and the load ratio increased. At the same time, the failure mechanism changed from ductile (striations) to brittle (hydrogen decohesion) with intergranular fracture (IG) becoming the predominant failure mechanism under the highest loads (R = 0.5). Full article
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16 pages, 4456 KiB  
Article
Experimental Investigation of Fracture Performances of SBHS500, SM570 and SM490 Steel Specimens with Notches
by Yan Liu, Shuto Ikeda, Yanyan Liu, Lan Kang and Hanbin Ge
Metals 2022, 12(4), 672; https://doi.org/10.3390/met12040672 - 14 Apr 2022
Cited by 4 | Viewed by 1777
Abstract
High-strength steels (HSSs) with nominal yield stress not less than 460 MPa have been increasingly employed in bridge structures. Compared with SM490 normal-strength steel (NSS), HSSs, including SBHS500 and SM570, have higher strength but lower ductility, and brittle fracture can easily occur in [...] Read more.
High-strength steels (HSSs) with nominal yield stress not less than 460 MPa have been increasingly employed in bridge structures. Compared with SM490 normal-strength steel (NSS), HSSs, including SBHS500 and SM570, have higher strength but lower ductility, and brittle fracture can easily occur in the HSSs members with notches. Therefore, 48 tension specimens with U-notch or V-notch made of SBHS500, SM570 and SM490 structural steels are carried out. The influences of notch depth, U-notch radius, V-notch degree and chemical composition on the mechanical and fracture performances of the steel specimens are investigated. It is concluded from experimental results that SBHS500 and SM570 HSSs with higher yield stress have a relatively higher elastic stress concentration factor, crack initiation appears earlier, and brittle fracture is more likely to occur. Compared to SM570 HSS, SBHS500 HSS has better weldability. Full article
(This article belongs to the Special Issue Modelling, Test and Practice of Steel Structures)
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10 pages, 5633 KiB  
Article
On the Heterogeneous Distribution of Secondary Precipitates in Friction-Stir-Welded 2519 Aluminium Alloy
by Ivan S. Zuiko, Sergey Malopheyev, Sergey Mironov, Sergey Betsofen and Rustam Kaibyshev
Metals 2022, 12(4), 671; https://doi.org/10.3390/met12040671 - 14 Apr 2022
Cited by 3 | Viewed by 1628
Abstract
The macro-scale distribution of secondary precipitates in friction-stir-welded 2519 aluminium alloy was studied. It was found that precipitation pattern essentially varied within the stir zone in terms of volume fraction, size, and even preferential concentration of the particles, either at grain boundaries or [...] Read more.
The macro-scale distribution of secondary precipitates in friction-stir-welded 2519 aluminium alloy was studied. It was found that precipitation pattern essentially varied within the stir zone in terms of volume fraction, size, and even preferential concentration of the particles, either at grain boundaries or within the grain interior. This effect was attributed to local variations in welding temperature and cooling rate, which led to complex precipitation phenomena including coarsening, dissolution, and partial reprecipitation. Specifically, the precipitation coarsening was most pronounced at the weld root due to the lowest welding temperature being in this area. On the other hand, the highest welding temperature at the upper weld surface enhanced the dissolution process. The reprecipitation phenomenon was deduced to be most prominent in the weld nugget due to the slowest cooling rate being in this microstructural region. Full article
(This article belongs to the Special Issue Advances in Welding and Mechanical Joining of Metals)
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21 pages, 6682 KiB  
Article
Numerical Modeling of Shockwaves Driven by High-Energy Particle Beam Radiation in Tungsten-Made Structures
by Martina Scapin and Lorenzo Peroni
Metals 2022, 12(4), 670; https://doi.org/10.3390/met12040670 - 14 Apr 2022
Viewed by 1754
Abstract
The investigation of wave propagation in solids requires the development of reliable methods for the prediction of such dynamic events in which the involved materials cover wide ranges of different possible states, governed by plasticity, equation of state, and failure. In the present [...] Read more.
The investigation of wave propagation in solids requires the development of reliable methods for the prediction of such dynamic events in which the involved materials cover wide ranges of different possible states, governed by plasticity, equation of state, and failure. In the present study, the wave propagation in metals generated by the interaction of high-energy proton beams with solids was considered. In this condition, axisymmetric waves were generated, and, depending on the amount of the delivered energy, different regimes (elastic, plastic, or shock) can be reached. Nonlinear numerical analyses were performed to investigate the material response. The starting point was the energy map delivered into the component as the consequence of the beam impact. The evolution of both hydrodynamic and mechanical quantities was followed starting from the impact and the effects induced on the hit component were investigated. The results showed the portion of the component close to the beam experiences pressure and temperature increase during the deposition phase. The remaining part of the component is traversed by the generated shockwave, which induces high values of strain in a short time or even the failure of the component. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials in Extreme Environments)
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14 pages, 2872 KiB  
Article
Research on Normal Contact Stiffness of Rough Joint Surfaces Machined by Turning and Grinding
by Yue Liu, Qi An, Deyong Shang, Long Bai, Min Huang and Shouqing Huang
Metals 2022, 12(4), 669; https://doi.org/10.3390/met12040669 - 14 Apr 2022
Cited by 4 | Viewed by 1953
Abstract
In order to accurately obtain the contact stiffness of rough joint surfaces machined by turning and grinding, a research simulation is carried out by using the finite element method. Based on the surface modeling method under the combined machining mode, the three-dimensional (3D) [...] Read more.
In order to accurately obtain the contact stiffness of rough joint surfaces machined by turning and grinding, a research simulation is carried out by using the finite element method. Based on the surface modeling method under the combined machining mode, the three-dimensional (3D) solid model is constructed. Then, the finite element results of the normal contact stiffness were obtained through contact analysis. The comparative analysis was carried out with the analytical results of the KE model and the experimental results. The comparison results show that three results have the same trend of change. However, the maximum relative error of the finite element results is 6.03%, while that of the analytical results for the KE model is 60.07%. After that, the finite element results under different machining parameters are compared. The normal contact stiffness increases with the increase in the turning tool arc radius, grinding depth, and fractal dimension, but decreases with the increase in the turning feed rate and scale coefficient. The rationality of the results is explained by the distribution of the asperities and the contact deformation law of the asperities on the rough surface. Full article
(This article belongs to the Special Issue Surface Modification of Metallic Materials for Wear and Fatigue)
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