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Metals, Volume 12, Issue 2 (February 2022) – 200 articles

Cover Story (view full-size image): Recently, Ag NPs have been used to produce conductive inks, which allows the construction of electronic devices on low-cost and flexible substrates using various printing techniques. This contribution presents a review of the synthesis of silver nanoparticles via different methods (chemical, physical, and biological methods) and the application of silver nanoparticles under the electrical field. Formulation of silver inks and formation of conductive patterns using different printing techniques (inkjet printing, screen printing and aerosol jet printing) are presented. The development of fast, efficient, and inexpensive sintering methods is also highlighted. View this paper
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14 pages, 11533 KiB  
Article
Evolution of Interface Microstructure and Tensile Properties of AgPd30/CuNi18Zn26 Bilayer Laminated Composite Manufactured by Rolling and Annealing
by Yong Wang, Yonghong Xu, Pei Zhang, Xianjun Yang and Yi Chen
Metals 2022, 12(2), 367; https://doi.org/10.3390/met12020367 - 21 Feb 2022
Cited by 3 | Viewed by 1917
Abstract
An AgPd30/CuNi18Zn26 bilayer laminated composite (BLC) was manufactured by hot-roll bonding followed by two passes of cold-rolling and three passes of annealing. The evolution of the interface microstructure during the manufacturing process was investigated using a scanning electron microscope, an electron probe microanalyzer, [...] Read more.
An AgPd30/CuNi18Zn26 bilayer laminated composite (BLC) was manufactured by hot-roll bonding followed by two passes of cold-rolling and three passes of annealing. The evolution of the interface microstructure during the manufacturing process was investigated using a scanning electron microscope, an electron probe microanalyzer, an X-ray diffractometer and a transmission electron microscope. It was found that a net atomic flow of Zn and Cu immigrated from the CuNi18Zn26 layer into the AgPd30 layer, leading to the formation of a Cu3Au-type superstructure of Cu2NiZn in the former and a diffusion layer in the later. The clusters enriched in Zn and Pd were formed in the diffusion layer and their number varied during the rolling and annealing process. The thickness of the diffusion layer was increased by annealing and decreased by cold rolling. Several intermetallic compounds were identified, which are Pd2Zn, PdZn, Pd2Zn3, PdZn2, Pd3Zn10 and Cu3Pd. Some orientation relationships between the compounds and the AgPd30 alloy were determined to be (310)PdZn2//(111)AgPd and (114)Cu3Pd//(311)PdZn2//(321)Pd3Zn10. Delamination occurred in all 6 samples during tensile testing, including an as-bonded one, two as-rolled ones and three as-annealed ones, but its degree decreased successively with the progress of rolling and annealing. Two turning points appear on the tensile curves of as-annealed samples, which are ascribed to the initiation of delamination and the yield of the metal matrix. However, the tensile curves of the as-bonded and as-rolled samples are smooth. Full article
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16 pages, 6721 KiB  
Article
Evolution of the Structural State and Properties of 32CrB4 Steel during the Production of High-Strength Fasteners
by Alexey Stepanov, Anton Koldaev, Nataliya Arutyunyan and Alexander Zaitsev
Metals 2022, 12(2), 366; https://doi.org/10.3390/met12020366 - 21 Feb 2022
Cited by 3 | Viewed by 2081
Abstract
For the production of high-strength fasteners, bar sections are used, which must withstand significant cold plastic deformation and, therefore, are subjected to a special heat treatment. In the present work, the dependences of the microstructure and mechanical properties of round bars with diameters [...] Read more.
For the production of high-strength fasteners, bar sections are used, which must withstand significant cold plastic deformation and, therefore, are subjected to a special heat treatment. In the present work, the dependences of the microstructure and mechanical properties of round bars with diameters of 17 mm and 21 mm made of 32CrB4 steel on the heat treatment modes are established. During the study, the methods of optical and scanning electron microscopy, mechanical tests, and hardness measurements were used. Dependences of the degree of spheroidization of the ferrite–pearlite structure and mechanical properties on the spheroidizing annealing mode have been established. It is shown that preliminary obtainment of a bainitic or martensitic structure of rolled products after hot-rolling of steel accelerates the process of pearlite spheroidization. Additional heat treatment, including austenitizing, quenching, and tempering, allows obtaining fasteners of various strength classes: 8.8, 9.8, and 10.9. However, with a guaranteed receipt of strength characteristics for all strength classes, including 12.9, the problem arises of achieving the required values of the relative elongation of steel. Full article
(This article belongs to the Section Metal Casting, Forming and Heat Treatment)
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14 pages, 7150 KiB  
Article
Microstructure Characteristics and Corrosion Behaviors of Mg-2Zn-2Er-0.3Zr-0.3Mn Alloy under Various Rolling Reductions
by Yaqi Zheng, Yuan Zhang, Yun Liu, Yaqiang Tian, Xiaoping Zheng and Liansheng Chen
Metals 2022, 12(2), 365; https://doi.org/10.3390/met12020365 - 21 Feb 2022
Cited by 3 | Viewed by 2282
Abstract
The poor corrosion resistance of magnesium alloys is one of the major obstacles to their widespread applications in the engineering field and the medical field. A hot deformation process is the main way to improve the corrosion resistance of magnesium alloys. In the [...] Read more.
The poor corrosion resistance of magnesium alloys is one of the major obstacles to their widespread applications in the engineering field and the medical field. A hot deformation process is the main way to improve the corrosion resistance of magnesium alloys. In the present study, X-ray photoelectron spectroscopy (XPS), a scanning electron microscope (SEM), an electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD) were used to investigate the micro-galvanic corrosion behavior and film protection mechanism of hot-rolled Mg-2Zn-2Er-0.3Zr-0.3Mn under 25%, 50% and 75% thickness reductions in Hank’s solution. The results revealed that the best corrosion resistance was obtained in the alloy under a 75% thickness reduction, with a corrosion rate of 0.85 mm/y. The improvement in anti-corrosion was due to the coupling effect of a refined microstructure and dense degradation film on the large deformation hot-rolled alloy. Furthermore, the elements Mn and Er participated in the film formation and stabilized the film structure. Full article
(This article belongs to the Section Biobased and Biodegradable Metals)
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15 pages, 9786 KiB  
Article
Microstructure, Hot Deformation Behavior, and Textural Evolution of Mg-3Sn-2Al-1Zn-0.6Nd Alloy
by Yuhang Guo, Yibo Dai, Pan Chen, Qianhao Zang and Zhenya Zhang
Metals 2022, 12(2), 364; https://doi.org/10.3390/met12020364 - 21 Feb 2022
Cited by 4 | Viewed by 1867
Abstract
To prepare wrought magnesium alloys with excellent plastic deformation properties, Mg-3Sn-2Al-1Zn-0.6Nd alloys were prepared. A hot compression test of Mg-3Sn-2Al-1Zn-0.6Nd alloy was carried out on a thermo-mechanical simulator. The hot deformation behavior of the alloys was studied, and the constitutive equations and the [...] Read more.
To prepare wrought magnesium alloys with excellent plastic deformation properties, Mg-3Sn-2Al-1Zn-0.6Nd alloys were prepared. A hot compression test of Mg-3Sn-2Al-1Zn-0.6Nd alloy was carried out on a thermo-mechanical simulator. The hot deformation behavior of the alloys was studied, and the constitutive equations and the processing map at the strain of 0.8 were established. The processing map exhibited the stable domain (temperature range of 320–350 °C and strain rate range of 0.001–0.04 s−1) with the high power dissipation efficiency (>30%). A large number of fine dynamic recrystallization (DRX) grains and deformed twinning existed in the alloy after the hot deformation. The dominant texture of the Mg-3Sn-2Al-1Zn-0.6Nd alloy is <0001>//CD texture after the hot deformation. The continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) were the dominant recrystallization mechanisms, and {101¯2} extension twinning also occurred in the alloy during the hot deformation. Full article
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15 pages, 5757 KiB  
Article
Study of the Fracture Behavior of TiN and TiC Inclusions in NM550 Wear-Resistant Steel during the Tensile Process
by Denghui Liu, Zhongyang Wang, Jingjing Liu, Zhenlong Wang and Xiurong Zuo
Metals 2022, 12(2), 363; https://doi.org/10.3390/met12020363 - 21 Feb 2022
Cited by 3 | Viewed by 2042
Abstract
NM550 wear-resistant steel is widely used in large-scale engineering and mining machinery under extremely harsh working conditions. In NM550 steel, the addition of Ti can cause the formation of micron-scale TiN and TiC inclusions, easily triggering cleavage fractures. The fracture behavior and precipitation [...] Read more.
NM550 wear-resistant steel is widely used in large-scale engineering and mining machinery under extremely harsh working conditions. In NM550 steel, the addition of Ti can cause the formation of micron-scale TiN and TiC inclusions, easily triggering cleavage fractures. The fracture behavior and precipitation rule of micron-scale TiN and TiC inclusions on the tensile process in NM550 steel was investigated by scanning electron microscopy, transmission electron microscopy, and energy spectrum analysis combined with thermodynamic theory. The TiN precipitated in the solid–liquid two-phase region at a precipitation temperature of 1710 K, whereas that of TiC was 1158 K along the austenite grain boundary. The sizes of the TiN precipitated in the liquid phase and the TiC precipitated in austenite were both at the micron scale, which is prone to cleavage fracture during the stretching process. Under tensile stress, microcracks were first initiated at the TiN inclusion, which were further separated forming a hole, whereas the TiC inclusion was divided into two sections with a long and narrow gap formed between the substrates. The sizes of the TiN and TiC were related to the cooling rate, Ti, and N contents. The larger the cooling rate and the lesser the Ti and N content, the smaller the TiN and TiC sizes. Full article
(This article belongs to the Special Issue Advanced Technology in Microalloyed Steels)
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18 pages, 8752 KiB  
Article
Tribological Performance of 100Cr6/8620 Steel Bearing System under Green Oil Lubrication
by Ricardo Ortega-Álvarez, María T. Hernández-Sierra, Luis D. Aguilera-Camacho, Micael G. Bravo-Sánchez, Karla J. Moreno and J. Santos García-Miranda
Metals 2022, 12(2), 362; https://doi.org/10.3390/met12020362 - 21 Feb 2022
Cited by 6 | Viewed by 2766
Abstract
There is a great need to perform all processes and services more efficiently to reduce energy consumption and material waste. Bearing systems are present in all machines and motors, playing an important role in the reduction of energy consumption. 100Cr6 (ISO 683-17:2014) and [...] Read more.
There is a great need to perform all processes and services more efficiently to reduce energy consumption and material waste. Bearing systems are present in all machines and motors, playing an important role in the reduction of energy consumption. 100Cr6 (ISO 683-17:2014) and AISI 8620 are two typical steels employed in most bearing systems. However, improving the tribological performance of these steels is still required. This study reports the analysis of green lubricants based on mixtures of vegetable oils to improve the friction and wear properties of steel bearing systems. Firstly, a method is presented to identify potential mixtures based on the excess thermodynamic properties. Then, the tribological performance of the 100Cr6/8620 steel bearing system lubricated with the selected mixtures is evaluated by the ball-on-disk method. It was found that the friction and wear behavior of the 100Cr6/8620 steel bearing system can be notably improved by the utilization of oil mixtures rather than pure green oils. The kinetic friction coefficient decreased up to 10% with the ideal mixture of castor and sesame oil, while wear was reduced up to 81% with the ideal mixture of castor and canola oil. Therefore, we suggest that vegetable oil blends may be a good option for the feasible manufacture of biolubricants for bearing systems. Full article
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2 pages, 174 KiB  
Editorial
Structure–Properties–Processing Relationships in Metallic Materials
by Spyros Papaefthymiou
Metals 2022, 12(2), 361; https://doi.org/10.3390/met12020361 - 21 Feb 2022
Viewed by 1405
Abstract
The steady innovation of materials has been assisted by the introduction of simulation and analytical technique tools in the development chain [...] Full article
(This article belongs to the Special Issue Structure-Properties-Processing Relationships in Metallic Materials)
11 pages, 5676 KiB  
Article
Texture Evolution by Strain-Induced Boundary Migration during Hot Deformation of Fe-3.0 wt.% Si Alloy: Experiment and Modeling
by Guangshuai Shao, Xi Chen, Yuhui Sha, Fang Zhang, Zhenghua He and Liang Zuo
Metals 2022, 12(2), 360; https://doi.org/10.3390/met12020360 - 20 Feb 2022
Cited by 1 | Viewed by 1649
Abstract
Texture and microstructure evolution during high-temperature plane-strain compression in Fe-3.0 wt.% Si alloy has been investigated by micro-texture analysis and modeling. In this study, hot deformation test is performed on the temperature range of 900 °C~1150 °C with a strain rate scope of [...] Read more.
Texture and microstructure evolution during high-temperature plane-strain compression in Fe-3.0 wt.% Si alloy has been investigated by micro-texture analysis and modeling. In this study, hot deformation test is performed on the temperature range of 900 °C~1150 °C with a strain rate scope of 0.01 s−1~5 s−1, and the effect of deformation parameters is investigated by means of electron backscattered diffraction. Nucleation and growth assisted by strain-induced boundary migration result in strong {001}<110> and {001}<210> texture components with low Taylor factors, and the grain size of λ fiber increases significantly by consuming the {111}<110> and {111}<112> texture components with high Taylor factors. The critical Taylor factor above which nucleation by strain-induced boundary migration cannot occur, decreases continuously during hot deformation. With the decreasing critical Taylor factor, the increment rate of low-Taylor-factor orientation depends more sensitively on Taylor factor than the decrement rate of high-Taylor-factor orientation. The boundary separating enhanced and weakened orientations moves towards lower Taylor factor with the deformation proceeding, and medium-Taylor-factor texture components may experience a reversed change from enhancement to weakness. A quantitative model is proposed to describe texture development by incorporating the oriented nucleation probability dependent on a variable critical Taylor factor and the selective growth driven by a variable Taylor factor difference between adjacent grains. The present work can provide an efficient method for optimizing hot deformation texture by means of strain-induced boundary migration. Full article
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16 pages, 15431 KiB  
Article
Rapid Spheroidizing Annealing via Combining Warm Deformation with Divorced Eutectoid Transformation in M50 Steel
by Dongsheng Qian, Bin Chen, Feng Wang and Lingyan Wu
Metals 2022, 12(2), 359; https://doi.org/10.3390/met12020359 - 20 Feb 2022
Cited by 1 | Viewed by 2094
Abstract
In this work, a novel routine to realize the rapid spheroidizing annealing (SA) process has been proposed in M50 steel via combining warm deformation (WD) and divorced eutectoid transformation (DET). In this process, the sample is first subjected to partial austenitizing to realize [...] Read more.
In this work, a novel routine to realize the rapid spheroidizing annealing (SA) process has been proposed in M50 steel via combining warm deformation (WD) and divorced eutectoid transformation (DET). In this process, the sample is first subjected to partial austenitizing to realize the partial dissolution of carbides, then slowly cooled to DET temperature for WD. Finally, the sample is slowly cooled to below the eutectoid transformation temperature to complete the SA. The results show that an excellent spheroidized microstructure can be obtained via the rapid SA process within 2 h. The finest spheroidized carbide (0.295 μm), as well as an appropriate hardness (217 HV), is achieved when the WD and DET processes are conducted at 760 °C. This should be attributed to that the WD not only accelerates the DET but also can break the primary carbides, leading to the uniformly distributed and refined carbides. In addition, the proposed WD that realizes rapid SA shows the excellent roundness of spheroidized carbides compared with the traditional cold/hot deformation which needs a long-term SA process. This work provides a highly efficient routine to simultaneously realize the SA and shape forming, which is of great engineering significance for the manufacturing of bearings. Full article
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13 pages, 4221 KiB  
Article
Joining of Zirconia to Ti6Al4V Using Ag-Cu Sputter-Coated Ti Brazing Filler
by Sónia Simões, Omid Emadinia, Carlos José Tavares and Aníbal Guedes
Metals 2022, 12(2), 358; https://doi.org/10.3390/met12020358 - 20 Feb 2022
Cited by 2 | Viewed by 1863
Abstract
The joining of zirconia (ZrO2) to Ti6Al4V using Ag-Cu sputter-coated Ti brazing filler foil was investigated. Brazing experiments were performed at 900, 950, and 980 °C for 30 min under vacuum. The microstructural features of the brazed interfaces were evaluated by [...] Read more.
The joining of zirconia (ZrO2) to Ti6Al4V using Ag-Cu sputter-coated Ti brazing filler foil was investigated. Brazing experiments were performed at 900, 950, and 980 °C for 30 min under vacuum. The microstructural features of the brazed interfaces were evaluated by optical microscopy (OM) and by scanning electron microscopy (SEM). The chemical composition of the brazed interfaces was analyzed by energy dispersive X-ray spectroscopy (EDS). Room temperature shear tests and Vickers microhardness tests performed across the interfaces were used to evaluate the mechanical strength of the joints. Multilayered interfaces were produced for all brazing temperatures, consisting essentially in α-Ti + Ti2(Ag, Cu), TiAg. Joining to ZrO2 was promoted by the formation of a hard layer, reaching a maximum of 1715 HV0.01, possibly consisting mainly in α-Ti and Ti oxide(s). Joining to the Ti6Al4V was established by a layer composed of a mixture of α-Ti and Ti2(Ag, Cu). The highest shear strength (152 ± 4 MPa) was obtained for brazing at 980 °C and fracture of joints occurred partially across the interface, throughout the hardest layers formed close to ZrO2, and partially across the ceramic sample. Full article
(This article belongs to the Special Issue Mechanical Characteristics of Brazed Joints in Metallic Materials)
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19 pages, 9226 KiB  
Article
Microstructure Analysis and Segmented Constitutive Model for Ni-Cr-Co-Based Superalloy during Hot Deformation
by Hongyu Li, Wei Feng, Wuhao Zhuang and Lin Hua
Metals 2022, 12(2), 357; https://doi.org/10.3390/met12020357 - 18 Feb 2022
Cited by 4 | Viewed by 2140
Abstract
In a thermal simulator of Gleeble-3500, isothermal hot compression tests were performed on a Ni-Cr-Co-based superalloy at deformation temperatures ranging from 1323 K to 1423 K and with strain rates of 0.01, 0.1, 1, and 5 s−1. We obtained the true [...] Read more.
In a thermal simulator of Gleeble-3500, isothermal hot compression tests were performed on a Ni-Cr-Co-based superalloy at deformation temperatures ranging from 1323 K to 1423 K and with strain rates of 0.01, 0.1, 1, and 5 s−1. We obtained the true stress–strain curves, and the microstructures of deformed samples were analyzed by electron backscatter diffraction (EBSD) technique. The segmented constitutive models were developed to predict the flow stress, and the dynamic recrystallization grain size model was established to evaluate the microstructure evolution for a Ni-Cr-Co-based superalloy. It is found that discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) appear simultaneously in the Ni-Cr-Co-based superalloy during hot deformation, with the latter not being active. Comparison between the experimental and predicted results indicates that the proposed models can describe and interpret the work-hardening and dynamic softening behaviors as well as the evolution characteristic of dynamic recrystallization grain size of the Ni-Cr-Co-based superalloy. In the error analysis of the segmented constitutive models, correlation coefficient (R) is 0.988 and average absolute relative error (AARE) is 6.94%, and for the AGS of DRX, R is 0.974 and AARE is 5.83%, which both have good accuracy. Full article
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20 pages, 9493 KiB  
Article
Effect of Intercritical Annealing Parameters and Starting Microstructure on the Microstructural Evolution and Mechanical Properties of a Medium-Mn Third Generation Advanced High Strength Steel
by Kazi M. H. Bhadhon, Xiang Wang, Elizabeth A. McNally and Joseph R. McDermid
Metals 2022, 12(2), 356; https://doi.org/10.3390/met12020356 - 18 Feb 2022
Cited by 13 | Viewed by 3021
Abstract
A prototype medium-Mn TRIP steel (0.2 C–6 Mn–1.7 Si–0.4 Al–0.5 Cr (wt %)) with a cold-rolled tempered martensite (CR) and martensitic (M) starting microstructures was subjected to continuous galvanizing line (CGL) compatible heat treatments. It was found that the M starting microstructures achieved [...] Read more.
A prototype medium-Mn TRIP steel (0.2 C–6 Mn–1.7 Si–0.4 Al–0.5 Cr (wt %)) with a cold-rolled tempered martensite (CR) and martensitic (M) starting microstructures was subjected to continuous galvanizing line (CGL) compatible heat treatments. It was found that the M starting microstructures achieved greater than 0.30 volume fraction of retained austenite and target 3G properties (UTS × TE ≥ 24,000 MPa%) using an intercritical annealing temperature (IAT) of 675 °C with an IA holding time of 60–360 s, whereas the CR microstructure required an IAT of 710 °C and annealing times of 360 s or greater to achieve comparable fractions of retained austenite and target 3G properties. This was attributed to the rapid austenite reversion kinetics for the M starting microstructures and rapid C partitioning from the C supersaturated martensite, providing chemical and mechanical stability to the retained austenite, thereby allowing for a gradual deformation-induced transformation of retained austenite to martensite—the TRIP effect—and the formation of nano-scale planar faults in the retained austenite (TWIP effect), such that a high work-hardening rate was maintained to elongation of greater than 0.20. Overall, it was concluded that the prototype steel with the M starting microstructure is a promising candidate for CGL processing for 3G AHSS properties. Full article
(This article belongs to the Special Issue Recent Developments in Medium and High Manganese Steels)
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22 pages, 11991 KiB  
Article
Deep Learning Approaches to Image Texture Analysis in Material Processing
by Xiu Liu and Chris Aldrich
Metals 2022, 12(2), 355; https://doi.org/10.3390/met12020355 - 18 Feb 2022
Cited by 18 | Viewed by 6843
Abstract
Texture analysis is key to better understanding of the relationships between the microstructures of the materials and their properties, as well as the use of models in process systems using raw signals or images as input. Recently, new methods based on transfer learning [...] Read more.
Texture analysis is key to better understanding of the relationships between the microstructures of the materials and their properties, as well as the use of models in process systems using raw signals or images as input. Recently, new methods based on transfer learning with deep neural networks have become established as highly competitive approaches to classical texture analysis. In this study, three traditional approaches, based on the use of grey level co-occurrence matrices, local binary patterns and textons are compared with five transfer learning approaches, based on the use of AlexNet, VGG19, ResNet50, GoogLeNet and MobileNetV2. This is done based on two simulated and one real-world case study. In the simulated case studies, material microstructures were simulated with Voronoi graphic representations and in the real-world case study, the appearance of ultrahigh carbon steel is cast as a textural pattern recognition pattern. The ability of random forest models, as well as the convolutional neural networks themselves, to discriminate between different textures with the image features as input was used as the basis for comparison. The texton algorithm performed better than the LBP and GLCM algorithms and similar to the deep learning approaches when these were used directly, without any retraining. Partial or full retraining of the convolutional neural networks yielded considerably better results, with GoogLeNet and MobileNetV2 yielding the best results. Full article
(This article belongs to the Special Issue Applications of Intelligent Process Systems in Metallurgy)
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15 pages, 7246 KiB  
Article
Role of Hot Rolling in Microstructure and Texture Development of Strip Cast Non-Oriented Electrical Steel
by Haitao Jiao, Xinxiang Xie, Xinyi Hu, Longzhi Zhao, Raja Devesh Kuma Misra, Dejia Liu, Yanchuan Tang and Yong Hu
Metals 2022, 12(2), 354; https://doi.org/10.3390/met12020354 - 18 Feb 2022
Cited by 4 | Viewed by 3875
Abstract
In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate [...] Read more.
In this study, the effect of the hot-cold rolling process on the evolution of the microstructure, texture and magnetic properties of strip-cast non-oriented electrical steel was investigated by introducing hot rolling with different reductions. The results indicate that hot rolling with an appropriate reduction, such as the 20% used in this study, increases the shear bands and {100} deformed microstructure in the cold roll sheet. As a result, in our study, enhanced η and Cube recrystallization texture and the improved magnetic induction were obtained. However, hot rolling with excessive reduction (36–52%) decreased the shear bands and increased the α-oriented deformation microstructure with low stored energy. It enhanced the α recrystallization texture and weakened the η texture, resulting in a decrease in the magnetic induction. In addition, hot rolling promoted the precipitation of supersaturated solid solution elements in the as-cast strip, thereby affecting the subsequent microstructure evolution and the optimization of its magnetic properties. Full article
(This article belongs to the Special Issue Texture, Microstructure and Properties of Electrical Steels)
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16 pages, 63658 KiB  
Article
In Situ X-ray Synchrotron Radiation Analysis, Tensile- and Biodegradation Testing of Redox-Alloyed and Sintered MgCa-Alloy Parts Produced by Metal Injection Moulding
by Martin Wolff, Heike Helmholz, Monika Luczak, Daniel Strerath, Thomas Ebel and Regine Willumeit-Römer
Metals 2022, 12(2), 353; https://doi.org/10.3390/met12020353 - 17 Feb 2022
Cited by 4 | Viewed by 1807
Abstract
Binary MgCa alloys are one of the promising and well investigated biodegradable metals and therefore a good standard for the study of novel processing routes. In this investigation, novel powder metallurgical (PM) blending and sintering methods were applied for the generation of biodegradable [...] Read more.
Binary MgCa alloys are one of the promising and well investigated biodegradable metals and therefore a good standard for the study of novel processing routes. In this investigation, novel powder metallurgical (PM) blending and sintering methods were applied for the generation of biodegradable MgCa test specimens, using metal injection moulding (MIM). In addition to the classical PM-blending route using Ca-containing master-alloys, Ca-containing ceramics and hydrides, as there are CaO and CaH2, were used separately and in a stoichiometric mixture. In situ X-ray synchrotron radiation experiments were performed for a deeper understanding of alloy forming mechanisms during sintering. Mechanical and degradation performance was investigated by tensile testing and the monitoring of biodegradation under physiological conditions. Besides its sound strength of up to 144 MPa and degradation rate of 0.25 mm/a, the new redox alloying technique avoids the usage of any greenhouse active SF6 gas (global warming potential 22,800) during alloying, keeping the earth’s atmosphere safer. Therefore, it can be concluded that Ca-containing ceramics and hybrids are attractive alternatives to obtain, comparable to Mg-based materials, thus enabling safer processing. Full article
(This article belongs to the Special Issue Powder Metallurgy of Biodegradable Metals for Medical Applications)
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13 pages, 2140 KiB  
Article
Corrosion Resistance of AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) High Entropy Alloys in NaCl and H2SO4 Solutions
by Svetlana Pratskova, Olga Samoilova, Egor Ageenko, Nataliya Shaburova, Ahmad Ostovari Moghaddam and Evgeny Trofimov
Metals 2022, 12(2), 352; https://doi.org/10.3390/met12020352 - 17 Feb 2022
Cited by 14 | Viewed by 2933
Abstract
The electrochemical behavior of as-cast AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) high entropy alloys (HEAs) in 1 M NaCl and 0.5 M H2SO4 solutions is studied. Polarization measurements were carried out in a standard three-electrode electrochemical [...] Read more.
The electrochemical behavior of as-cast AlxCoCrFeNiM (M = Ti, V, Si, Mn, Cu) high entropy alloys (HEAs) in 1 M NaCl and 0.5 M H2SO4 solutions is studied. Polarization measurements were carried out in a standard three-electrode electrochemical cell with a platinum auxiliary electrode using a P-30J potentiostat device. The potentials were measured relative to a saturated silver chloride reference electrode EVL-1M3 at room temperature (25 °C) with a sweep rate of 5 mV/s. It is shown that despite a wide passivation region, Al0.5CoCrFeNi1.6Ti0.7 HEA undergoes significant corrosion in both sodium chloride and sulfuric acid solutions and exhibits low corrosion potential and current density. Energy-dispersive X-ray spectroscopy (EDS) analysis revealed that Ti-containing eutectic areas are the most susceptible regions to corrosion. Intergranular corrosion was found in Al0.25CoCrFeNiMn and Al0.25CoCrFeNiCu HEAs. Moreover, Al0.25CoCrFeNiCu possesses the smallest passivation interval ΔE among all the investigated HEAs. For samples with Ti, Mn, and Cu, a protective film layer is not formed on the surface of the phases enriched in these elements, or it is brittle and crumbles. For samples with Si and V, a passivating film is formed. Thus, Al0.45CoCrFeNiSi0.45 and Al0.25CoCrFeNiV HEAs exhibited the highest resistance in 1 M NaCl and 0.5 M H2SO4 corrosive environments, respectively. Full article
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17 pages, 76036 KiB  
Article
Numerical Simulation and Defect Identification in the Casting of Co-Cr Alloy
by Raimundo Silva, Rui Madureira, José Silva, Rui Soares, Ana Reis, Rui Neto, Filomena Viana, Omid Emadinia and Rui Silva
Metals 2022, 12(2), 351; https://doi.org/10.3390/met12020351 - 17 Feb 2022
Cited by 5 | Viewed by 2775
Abstract
The development of biomaterials, particularly metallic ones, is one of the focuses of the scientific community, mainly due to an increase of average life expectancy and an improvement of the casted materials combined with better mechanical properties and defect-free products. The use of [...] Read more.
The development of biomaterials, particularly metallic ones, is one of the focuses of the scientific community, mainly due to an increase of average life expectancy and an improvement of the casted materials combined with better mechanical properties and defect-free products. The use of cobalt alloys in applications, such as knee, hip, and dental prostheses, is the result of their good ability to maintain mechanical properties and biocompatibility over long periods of use. Numerical methods are becoming more important, as they help product improvement in a faster and economic way. This work focuses on the development of a numerical model in ProCAST®, comparing the shrinkage porosity and cooling curves with real castings. When correlating simulation results with available experimental data, it is possible to understand that the formulated model demonstrates an acceptable solution in terms of precision (shrinkage porosity and cooling curve). The alloy’s thermal properties and heat conditions were iteratively changed until the developed numerical model turned out a viable tool for this specific alloy when used in the investment casting process. Full article
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11 pages, 3514 KiB  
Article
Erosion Layer Growth between Solid 316L Stainless Steel and Al–Li Alloy Melt
by Zhanwei He, Xiaojun Hu, Wan Han, Xudong Mao and Kuo-Chih Chou
Metals 2022, 12(2), 350; https://doi.org/10.3390/met12020350 - 17 Feb 2022
Cited by 2 | Viewed by 1511
Abstract
The erosion experiments of Al–Li melt on 316L stainless steel were carried out at different temperatures and holding times. In this study, the microstructure and composition of an Al–Li/316L liquid–solid interface was analyzed by inductively coupled plasma atomic emission spectroscope (ICP-AES), scanning electron [...] Read more.
The erosion experiments of Al–Li melt on 316L stainless steel were carried out at different temperatures and holding times. In this study, the microstructure and composition of an Al–Li/316L liquid–solid interface was analyzed by inductively coupled plasma atomic emission spectroscope (ICP-AES), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The phase transformation and structure evolution of the erosion process were studied to explain the erosion mechanism and kinetics. The results showed that Fe/Cr/Ni–Al intermetallic compounds (IMC) were formed at the Al–Li/316L interface, and the diffusion of Cr atoms lead to the accumulation of Ti in the Al–Li melt, to form TiAl3 and CrAl4. With the increase in temperature and holding time, the thickness of the Fe-containing erosion layer (EL) increased, and the morphology of Ti-containing erosion particles (EP) became larger and more regular. The apparent activation energy (Ea) of the Fe-containing erosion layer was 124.82 kJ·mol−1. Meanwhile, a kinetics equation for predicting the service life of 316L was obtained. The research results provided a theoretical guidance for the smelting and casting of an Al–Li alloy. Full article
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11 pages, 2184 KiB  
Article
Towards a Data Lake for High Pressure Die Casting
by Maximilian Rudack, Michael Rath, Uwe Vroomen and Andreas Bührig-Polaczek
Metals 2022, 12(2), 349; https://doi.org/10.3390/met12020349 - 17 Feb 2022
Cited by 3 | Viewed by 3420
Abstract
The High Pressure Die Casting (HPDC) process is characterized by a high degree of automation and therefore represents a data rich production technology. From concepts such as Industry 4.0 and the Internet of Production (IoP), it is well known that the utilization of [...] Read more.
The High Pressure Die Casting (HPDC) process is characterized by a high degree of automation and therefore represents a data rich production technology. From concepts such as Industry 4.0 and the Internet of Production (IoP), it is well known that the utilization of process data can facilitate improvements in product quality and productivity. In this work, we present a concept and its first steps of implementation to enable data management via a data lake for HPDC. Our goal was to design a system capable of acquiring, transmitting and storing static as well as dynamic process variables. The measurements originate from multiple data sources based on the Open Platform Communication Unified Architecture (OPC UA) within the HPDC cell and are transmitted via a streaming pipeline implemented in Node-Red and Apache Kafka. The data are consecutively stored in a data lake for HPDC that is based on a MinIO object store. In initial tests the implemented system proved it to be reliable, flexible and scalable. On standard consumer hardware, data handling of several thousand measurements per minute is possible. The use of the visual programming language Node-Red enables swift reconfiguration and deployment of the data processing pipeline. Full article
(This article belongs to the Special Issue Advances in Metal Casting Technology)
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17 pages, 10311 KiB  
Article
Enhancement of Wear Resistance on H13 Tool and Die Steels by Trace Nanoparticles
by Shu-Qing Kou, Jun-Nan Dai, Wen-Xin Wang, Chun-Kai Zhang, Si-Yu Wang, Tai-Yu Li and Fang Chang
Metals 2022, 12(2), 348; https://doi.org/10.3390/met12020348 - 16 Feb 2022
Cited by 4 | Viewed by 2680
Abstract
In order to improve the impact toughness and wear resistance of the tool and die steels, this study innovatively prepared strengthened H13 steels with different contents of single-phase TiC and dual-phase TiC + TiB2 through in situ nanoparticle/Al master alloys at room [...] Read more.
In order to improve the impact toughness and wear resistance of the tool and die steels, this study innovatively prepared strengthened H13 steels with different contents of single-phase TiC and dual-phase TiC + TiB2 through in situ nanoparticle/Al master alloys at room temperature. The microstructure evolution and mechanical properties as well as wear resistance were investigated. Results indicate that the H13 steel with 0.02 wt.% dual-phase TiC + TiB2 nanoparticles has a more uniform and finer microstructure, and the mechanical properties and wear resistance are significantly improved. The yield strength, maximum tensile strength, breaking strain, uniform elongation, product of strength plasticity, and unnotched and U-notched impact toughness of H13 steel with 0.02 wt.% dual-phase TiC + TiB2 are higher than that of H13 steel. In addition, the volume wear rate, maximum scratch depth and width reach 7.1 × 10−11 m3/m, 6050 nm and 90 μm, respectively, which are reduced by 44.5%, 30.1% and 45.5% compared with that of H13 steel. Refining the microstructure and improving impact toughness and wear resistance of H13 tool steel through trace nanoparticles can provide important inspiration for industrial applications. Full article
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22 pages, 1690 KiB  
Article
Theoretical Study on Thermal Stresses of Metal Bars with Different Moduli in Tension and Compression
by Ying Guo, Si-Rui Wen, Jun-Yi Sun and Xiao-Ting He
Metals 2022, 12(2), 347; https://doi.org/10.3390/met12020347 - 16 Feb 2022
Cited by 6 | Viewed by 2160
Abstract
Extensive studies have shown that engineering materials, including metals and their oxides, will present different mechanical properties in tension or compression; however, this difference is generally neglected due to the complexity of the analysis. In this study, we theoretically analyze the thermal stress [...] Read more.
Extensive studies have shown that engineering materials, including metals and their oxides, will present different mechanical properties in tension or compression; however, this difference is generally neglected due to the complexity of the analysis. In this study, we theoretically analyze the thermal stress of a metal bar with a bimodular effect. First, the common strain suppression method is used to obtain a one-dimensional thermal stress expression. As a contrast with the one-dimensional solution, a two-dimensional thermoelasticity solution is also derived, based on the classical Duhamel theorem concerning body force analogy. Results indicate an important phenomenon that the linear temperature rise mode will produce thermal stress in a bimodular metal bar, whereas there is no thermal stress in the case of singular modulus. If the equilibrium relation is needed to be satisfied, the variation trend between different moduli and different thermal expansion coefficients in tension and compression should be opposite. In addition, the amplitude of stress variation, from the maximum tensile stress to the maximum compressive stress, increases dramatically. There exists an inevitable link between one- and two-dimensional solutions. These results are helpful to the refined analysis and measurements of the thermophysical properties of metals and their oxides. Full article
(This article belongs to the Special Issue Thermo-Physical Properties of Metals and Oxides)
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25 pages, 96857 KiB  
Article
Effects of Low-Frequency Vibrations on Single Point Incremental Sheet Forming
by Xiao Xiao, Se-Hyeon Oh, Sang-Hoon Kim and Young-Suk Kim
Metals 2022, 12(2), 346; https://doi.org/10.3390/met12020346 - 16 Feb 2022
Cited by 4 | Viewed by 2676
Abstract
This study investigated the effects of longitudinal low-frequency vibrations on the performance of the single point incremental forming process of an aluminum alloy 1050 (AA1050) sheet. Low-frequency vibrations were added to the forming tool’s axial movement. A finite element model of low-frequency vibration [...] Read more.
This study investigated the effects of longitudinal low-frequency vibrations on the performance of the single point incremental forming process of an aluminum alloy 1050 (AA1050) sheet. Low-frequency vibrations were added to the forming tool’s axial movement. A finite element model of low-frequency vibration single point incremental forming was established. Numerical simulation analyzed the effect of low-frequency vibrations on the entire forming process. Then, the simulation results were verified through actual experiments. The results showed that low-frequency vibrations could significantly reduce the forming force and improve the formed product’s geometric accuracy. Full article
(This article belongs to the Topic Advanced Forming Technology of Metallic Materials)
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14 pages, 17378 KiB  
Article
The Effect of Symmetrically Tilt Grain Boundary of Aluminum on Hydrogen Diffusion
by Yuhao Wang, Haijun Wang, Lingxiao Li, Jiyan Liu, Pei Zhao and Zhiqiang Xu
Metals 2022, 12(2), 345; https://doi.org/10.3390/met12020345 - 16 Feb 2022
Cited by 2 | Viewed by 2212
Abstract
High-strength aluminum alloys are widely used in industry. Hydrogen embrittlement greatly reduces the performance and service safety of aluminum alloys. The hydrogen traps in alumi-num profoundly affect the hydrogen embrittlement of aluminum. Here, we took a coinci-dence-site lattice (CSL) symmetrically tilted grain boundary [...] Read more.
High-strength aluminum alloys are widely used in industry. Hydrogen embrittlement greatly reduces the performance and service safety of aluminum alloys. The hydrogen traps in alumi-num profoundly affect the hydrogen embrittlement of aluminum. Here, we took a coinci-dence-site lattice (CSL) symmetrically tilted grain boundary (STGB) Σ5(120)[001] as an example to carry out molecular dynamics (MD) simulations of hydrogen diffusion in aluminum at dif-ferent temperatures, and to obtain results and rules consistent with the experiment. At 700 K, three groups of MD simulations with concentrations of 0.5, 2.5 and 5 atomic % hydrogen (at. % H) were carried out for STGB models at different angles. By analyzing the simulation results and the MSD curves of hydrogen atoms, we found that, in the low hydrogen concentration of STGB models, the grain boundaries captured hydrogen atoms and hindered their movement. In high-hydrogen-concentration models, the diffusion rate of hydrogen atoms was not affected by the grain boundaries. The analysis of the simulation results showed that the diffusion of hydro-gen atoms at the grain boundary is anisotropic. Full article
(This article belongs to the Special Issue Review of Hydrogen Embrittlement in Metals)
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13 pages, 2666 KiB  
Article
Kinetics of Carbon Partitioning of Q&P Steel: Considering the Morphology of Retained Austenite
by Yaowen Xu, Fei Chen, Zhen Li, Gengwei Yang, Siqian Bao, Gang Zhao, Xinping Mao and Jun Shi
Metals 2022, 12(2), 344; https://doi.org/10.3390/met12020344 - 16 Feb 2022
Cited by 5 | Viewed by 2429
Abstract
The diffusion of carbon atoms from martensite to retained austenite (RA) is controlled by the carbon partitioning kinetics when the quenching and partitioning (Q&P) process is conducted. The RA is divided into film-like and blocky ones in morphology. This research aims to study [...] Read more.
The diffusion of carbon atoms from martensite to retained austenite (RA) is controlled by the carbon partitioning kinetics when the quenching and partitioning (Q&P) process is conducted. The RA is divided into film-like and blocky ones in morphology. This research aims to study the influence of the morphology of RA on the kinetics of carbon partitioning mainly by developing a numerical simulation. A one-step Q&P process was modeled at the partitioning temperature of 330–292 °C, with a partitioning time ranging from 106 to 5 × 103 s. The finite element method was employed to solve the carbon diffusion equation. A thermomechanical simulator Gleeble-3500 was used to conduct the corresponding Q&P heat treatment, and the RA was examined by X-ray diffraction. The results show that the film-like RA will be enriched in carbon within a short time at first, followed by a decrease in carbon concentration due to the massive absorption of carbon by blocky RA, leading the stable film-like RA to become unstable again. The end of the kinetics of carbon partitioning was the concentration determined by the constrained carbon equilibrium (CCE) model, provided that the CCE condition was employed in this study. It took quite a long time (thousands of seconds) to complete the carbon partitioning globally, which was influenced by the partitioning temperature. Full article
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17 pages, 3992 KiB  
Article
Investigation of Spatter Trajectories in an SLM Build Chamber under Argon Gas Flow
by Awad B. S. Alquaity and Bekir S. Yilbas
Metals 2022, 12(2), 343; https://doi.org/10.3390/met12020343 - 16 Feb 2022
Cited by 5 | Viewed by 2597
Abstract
Spatter particles ejected from the melt pool during selective laser melting processes can get redeposited on the build plate region and impact final part quality. Although an inert gas flow is used to purge the spattered particles away from the build plate region, [...] Read more.
Spatter particles ejected from the melt pool during selective laser melting processes can get redeposited on the build plate region and impact final part quality. Although an inert gas flow is used to purge the spattered particles away from the build plate region, some of the spatter particles get redeposited on the plate region leading to increased porosity and surface roughness. In this regard, the current study focuses on the numerical modeling of the interactions between the inert gas flow and spatter particles by using the discrete phase model. A Renishaw AM250 build chamber is used as the base geometry and the flow field within the build chamber is evaluated for various inert gas flow rates and nozzle diameters of 6 mm and 12 mm. For the first time, spatter trajectories are tracked at specific spatter diameters and ejection angles to pinpoint the influence of drag and gravitational forces on the evolution of spatter trajectories. The findings reveal that the spatter particles between 120 and 180 μm diameter travel beyond the build plate only at specific gas ejection angles and gas flow rates (≥750 L/min). Reducing the nozzle diameter to 6 mm increases the inert gas flow velocity in the build region and enhances the range of spatter particles. New correlations are proposed to relate the range of particles and inert gas flow rates, which can be used to identify the spatter diameters, ejection angles, and inert gas flow rates required to transport the particles beyond the sensitive build plate region. Full article
(This article belongs to the Special Issue Optimization of Metal Additive Manufacturing Processes)
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25 pages, 95211 KiB  
Article
Benchmarking a 9Cr-2WVTa Reduced Activation Ferritic Martensitic Steel Fabricated via Additive Manufacturing
by Tim Gräning and Niyanth Sridharan
Metals 2022, 12(2), 342; https://doi.org/10.3390/met12020342 - 15 Feb 2022
Cited by 10 | Viewed by 2635
Abstract
Reduced activation ferritic (RAF) martensitic steels are promising candidates for the first wall of fusion reactors. However, current manufacturing capabilities call for these components to be made by welding wrought plates. This limits design freedom and necessitates the use of post-weld heat treatments [...] Read more.
Reduced activation ferritic (RAF) martensitic steels are promising candidates for the first wall of fusion reactors. However, current manufacturing capabilities call for these components to be made by welding wrought plates. This limits design freedom and necessitates the use of post-weld heat treatments (PWHT) in accordance with the boiler and pressure vessel code. Additive manufacturing (AM) can offer a unique solution to solve this challenge by leveraging the layer-wise deposition strategy to come up with temper bead deposition techniques to eliminate post-processing heat treatments (PPHT). However, it is necessary to benchmark the properties of RAF steels fabricated by AM with their wrought counterparts to identify the process-structure-property correlation, which is the goal of this study. The study demonstrates that while tensile properties at room temperature and high temperatures are satisfactory, the as fabricated and samples after PPHT have significant heterogeneity in tensile elongation. This has been attributed to the presence of discontinuities in the build. The as-fabricated samples have an average tensile strength of 1190 + 12 MPa and an average elongation of 15 + 5% at room temperature and 658 ± 20 MPa ultimate tensile strength (UTS) and 14 ± 7% at 600 °C. After the post-weld heat treatment, mechanical properties decrease to around 600–650 MPa and an elongation between 20–25% at room temperature to 300 MPa UTS and 25–28% elongation at 600 °C. The characterization of microstructures at various length scales demonstrates that the as-fabricated structure has a significant fraction of delta ferrite in a lath martensitic matrix. No precipitates could be identified in the as-fabricated structure. PPHT led to a decrease in the area fraction of delta ferrite and precipitation of M23C6 and MX. Detailed characterization clearly demonstrates that the lack of precipitates in the as-fabricated structure could be due to the slow tempering response of the alloy. Finally, the needs to develop new alloys to achieve the objectives stated above are articulated. Full article
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27 pages, 50279 KiB  
Review
Recent Advances in Magnetostrictive Tb-Dy-Fe Alloys
by Zijing Yang, Jiheng Li, Zhiguang Zhou, Jiaxin Gong, Xiaoqian Bao and Xuexu Gao
Metals 2022, 12(2), 341; https://doi.org/10.3390/met12020341 - 15 Feb 2022
Cited by 10 | Viewed by 3274
Abstract
As giant magnetostrictive materials with low magnetocrystalline anisotropy, Tb-Dy-Fe alloys are widely used in transducers, actuators and sensors due to the effective conversion between magnetic energy and mechanical energy (or acoustic energy). However, the intrinsic brittleness of intermetallic compounds leads to their poor [...] Read more.
As giant magnetostrictive materials with low magnetocrystalline anisotropy, Tb-Dy-Fe alloys are widely used in transducers, actuators and sensors due to the effective conversion between magnetic energy and mechanical energy (or acoustic energy). However, the intrinsic brittleness of intermetallic compounds leads to their poor machinability and makes them prone to fracture, which limits their practical applications. Recently, the addition of a fourth element to Tb-Dy-Fe alloys, such as Ho, Pr, Co, Nb, Cu and Ti, has been studied to improve their magnetostrictive and mechanical properties. This review starts with a brief introduction to the characteristics of Tb-Dy-Fe alloys and then focuses on the research progress in recent years. First, studies on the crystal growth mechanism in directional solidification, process improvement by introducing a strong magnetic field and the effects of substitute elements are described. Then, meaningful progress in mechanical properties, composite materials, the structural origin of magnetostriction based on ferromagnetic MPB theory and sensor applications are summarized. Furthermore, sintered composite materials based on the reconstruction of the grain boundary phase also provide new ideas for the development of magnetostrictive materials with excellent comprehensive properties, including high magnetostriction, high mechanical properties, high corrosion resistance and high resistivity. Finally, future prospects are presented. This review will be helpful for the design of novel magnetostrictive Tb-Dy-Fe alloys, the improvement of magnetostrictive and mechanical properties and the understanding of magnetostriction mechanisms. Full article
(This article belongs to the Special Issue Advances in Metal-Containing Magnetic Materials)
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20 pages, 5130 KiB  
Article
Experimental and Numerical Vibration Analysis of Octet-Truss-Lattice-Based Gas Turbine Blades
by Sajjad Hussain, Wan Aizon W. Ghopa, S. S. K. Singh, Abdul Hadi Azman and Shahrum Abdullah
Metals 2022, 12(2), 340; https://doi.org/10.3390/met12020340 - 15 Feb 2022
Cited by 16 | Viewed by 3816
Abstract
This paper aims to investigate the utilization of octet truss lattice structures in gas turbine blades to achieve weight reduction and improvement in vibration characteristics, which are desired for turbine blades to improve the efficiency and load capacity of turbines. A solid blade [...] Read more.
This paper aims to investigate the utilization of octet truss lattice structures in gas turbine blades to achieve weight reduction and improvement in vibration characteristics, which are desired for turbine blades to improve the efficiency and load capacity of turbines. A solid blade model using NACA 23012 airfoil was designed as reference. Three lattice-based blades were designed and manufactured via additive manufacturing by replacing the internal volume of solid blades with octet truss unit cells of variable strut thickness. Experimental and numerical vibration analyses were performed on the blades to establish their suitability for potential use in turbine blades. A maximum weight reduction of 24.91% was achieved. The natural frequencies of lattice blades were higher than those of solid blades. A stress reduction up to 38.6% and deformation reduction of up to 21.5% compared with solid blades were also observed. Both experimental and numerical results showed good agreement with a maximum difference of 3.94% in natural frequencies. Therefore, apart from being lightweight, octet-truss-lattice-based blades have excellent vibration characteristics and low stress levels, thereby making these blades ideal for enhancing the efficiency and durability of gas turbines. Full article
(This article belongs to the Topic Additive Manufacturing)
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21 pages, 9229 KiB  
Article
Fatigue Life and Reliability of Steel Castings through Integrated Simulations and Experiments
by Muhammad Azhar Ali Khan, Anwar Khalil Sheikh, Zuhair Mattoug Gasem and Muhammad Asad
Metals 2022, 12(2), 339; https://doi.org/10.3390/met12020339 - 15 Feb 2022
Cited by 3 | Viewed by 2715
Abstract
The quality and performance of steel castings is always a concern due to porosities formed during solidification of the melt. Nowadays, computational tools are playing a pivotal role in analyzing such defects, followed by their minimization through mold design optimization. Even if the [...] Read more.
The quality and performance of steel castings is always a concern due to porosities formed during solidification of the melt. Nowadays, computational tools are playing a pivotal role in analyzing such defects, followed by their minimization through mold design optimization. Even if the castings are produced with defects in a permissible range, it is important to examine their service life and performance with those defects in a virtual domain using simulation software. This paper aims to develop a methodology with a similar idea of simulation-based optimization of mold design and predictions of life and reliability of components manufactured with minimized casting defects, especially porosities. The cast parts are standard fatigue specimens which are produced through an optimized multi-cavity mold. X-ray imaging is done to determine the soundness of cast parts. Experimental work includes load-controlled fatigue testing under fully reversed condition. The fatigue life of specimens is also simulated and compared with the experimental results. The classical strength-stress model is used to determine the reliability of cast parts through which a safe-load induced stress of steel castings is determined. Finally, probability distributions are fit to the reliability results to develop the reliability models. It is found that porosities can be minimized significantly in the mold design phase using casting simulations. Nevertheless, some porosities are bound to exist, which must be included in realistic estimation of fatigue life and reliability of cast parts. Full article
(This article belongs to the Special Issue Computational Methods for Fatigue and Fracture)
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8 pages, 3118 KiB  
Communication
Fabrication of Precursor by Consolidating Aluminum Alloy Powder Using Friction Stir Welding and Its Foaming
by Yoshihiko Hangai, Hiromi Morohashi and Hironao Mitsugi
Metals 2022, 12(2), 338; https://doi.org/10.3390/met12020338 - 15 Feb 2022
Cited by 1 | Viewed by 1485
Abstract
In this study, we fabricated a precursor by FSW using ADC12 (Al-Si-Cu alloy) powder and foamed the obtained precursor by optical heating to fabricate the porous aluminum (Al). If ADC12 powder can be used for fabricating the precursor, it is expected that Al [...] Read more.
In this study, we fabricated a precursor by FSW using ADC12 (Al-Si-Cu alloy) powder and foamed the obtained precursor by optical heating to fabricate the porous aluminum (Al). If ADC12 powder can be used for fabricating the precursor, it is expected that Al waste materials from the manufacturing of industrial products, such as Al cutting scraps, can be used as recycled Al chips, with which the cost of porous Al manufacturing can be reduced. The results demonstrated that ADC12 powder can be consolidated as well as the blowing agent (titanium hydride) and stabilization agent (alumina) powders can be mixed into the consolidated ADC12 by FSW to fabricate precursors at the tool traversing speed v = 10–50 mm/min. In addition, the obtained precursor can be foamed by optical heating. It was also found that the precursor with fewer cracks and defects can be obtained at v = 10, 20, and 30 mm/min versus at v = 40 and 50 mm/min. As a result, porous Al with relatively good pore structures was obtained at v = 10–30 mm/min. Full article
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