Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 17960

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Faculty of Technical and Economic Sciences, Witelon Collegium State University, Sejmowa 5A, 59-220 Legnica, Poland
Interests: foundry; material engineering; metals; composites; mechanical properties; corrosion; wear; heat treatment; management and production engineering
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Special Issue Information

Dear Colleagues,

Crystalline materials are the most commonly used materials. Thanks to their crystalline structure, they are characterized by a number of beneficial properties, including mechanical properties, functional properties, and exploitation properties. In recent years, many discoveries and advances have been made in materials engineering, which materials scientists are using to create countless new materials through the use of modern modeling and simulation systems, technologies, and manufacturing techniques that enable obtaining advanced materials. These materials include high-quality construction materials, composites, and nanomaterials. For many of the emerging material solutions today, the main focus is on the mechanical properties of the materials. As a result, they are used on a large scale in land and water construction, automotive, aviation, and space engineering, as well as in the power industry.

Mechanical properties are an extremely important metric for evaluating materials, as they determine which areas the materials can be used in. Hardness and strength are the main mechanical properties. The values of these quantities are usually correlated. In order to obtain high hardness/strength, treatments are used to strengthen the structure, and they consist in the appropriate selection of chemical composition and technological processes. These activities must guarantee that a structure is obtain that ensures high hardness and strength. The obtained materials are usually hard and statically strong, but most often also brittle. Because they are not plastic, they have poor impact strength and are not resistant to abrasive wear, considering dynamic factors. Therefore, achieving a high synergy between strength and ductility is a major challenge and has become a topic of general interest.

From the point of view of exploitation of structural elements, machines, and devices, factors reducing their ability to transfer external loads are also important. These factors include corrosion and wear.

Simulation and modeling processes play a key role in facilitating the rapid dissemination of advanced materials and reaping the benefits they offer. This is of great importance for production processes, in terms of costs and product quality. The modeling and simulation of production processes are the best and most cost-effective methods of testing and evaluating the properties of advanced materials in terms of the usability and the quality of the resulting product. Modeling and simulations also enable an easier and cheaper assessment of the effectiveness of production processes and systems, also from the point of view of their management.

In the proposed Special Issue, we are looking for research and review papers on technology, microstructure, mechanical properties, and various applications of crystalline materials. We invite you to submit works that include modeling and simulation of production processes and systems and their management in production, as well as forecasts of the future development of materials and production systems. Potential topics include, but are not limited to,

  • Alloy design and manufacturing of crystalline materials;
  • Crystalline nanomaterials and composites;
  • Mechanical properties and fracture mechanics;
  • Crystalline materials for power engineering;
  • Casting, welding, and additive manufacturing;
  • Advanced heat treatment techniques;
  • Materials design and modeling and applications in production processes and their management;

We cordially invite you to submit your manuscripts to this Special Issue. Original research articles, perspectives, and reviews are welcome.

Dr. Daniel Medyński
Dr. Grzegorz Lesiuk
Dr. Anna Burduk
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • metals and alloys
  • nanomaterials
  • composites
  • solidification and crystallization
  • phase transformations
  • materials modelling
  • casting and welding
  • additive manufacturing
  • heat treatment
  • corrosion
  • mechanical properties
  • fracture mechanics
  • production management
  • production processes and systems

Published Papers (17 papers)

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Research

12 pages, 2955 KiB  
Article
The Relationship between Polishing Method and ISE Effect
by Jozef Petrík, Peter Blaško, Dagmar Draganovská, Sylvia Kusmierczak, Marek Šolc, Miroslava Ťavodová and Mária Mihaliková
Crystals 2023, 13(12), 1633; https://doi.org/10.3390/cryst13121633 - 25 Nov 2023
Viewed by 628
Abstract
The aim of the submitted work is to study the relationship between the method of polishing the metallurgical surface and the indentation size effect (ISE). The material of the sample was annealed 99.5% aluminum. The polishing time ranged between 300 and 3600 s. [...] Read more.
The aim of the submitted work is to study the relationship between the method of polishing the metallurgical surface and the indentation size effect (ISE). The material of the sample was annealed 99.5% aluminum. The polishing time ranged between 300 and 3600 s. An aqueous emulsion of aluminum oxide (spineline) and diamond paste were used as the polishing agents. The surface quality of the samples was measured with roughness meters. Applied loads in the micro-hardness test were 0.0981, 0.2452, 0.4904, and 0.9807 N. The effect of polishing on micro-hardness, Meyer’s index n, and ISE characteristics was evaluated using the PSR method and the Hays–Kendall approach. As the polishing time increases, the micro-hardness values decrease, and the value of Meyer’s index n increases from “normal” to neutral, i.e., Kick’s law applies. The finding was confirmed for both of the used polishing agents. Full article
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17 pages, 5374 KiB  
Article
Numerical Simulation of Temperature Field during Electron Beam Cladding for NiCrBSi on the Surface of Inconel 718
by Guanghui Zhao, Yu Zhang, Juan Li, Huaying Li, Lifeng Ma and Yugui Li
Crystals 2023, 13(9), 1372; https://doi.org/10.3390/cryst13091372 - 14 Sep 2023
Cited by 1 | Viewed by 869
Abstract
This study investigates the Inconel 718 alloy coated with NiCrBSi powder using the ABAQUS software. An accurate conical heat source model is constructed based on the three-dimensional Fourier heat conduction law. The heat source subroutine Dflux.for is successfully integrated to achieve a highly [...] Read more.
This study investigates the Inconel 718 alloy coated with NiCrBSi powder using the ABAQUS software. An accurate conical heat source model is constructed based on the three-dimensional Fourier heat conduction law. The heat source subroutine Dflux.for is successfully integrated to achieve a highly realistic simulation of the welding heat source. Using this model, the analysis focuses on the temperature distribution in electron beam melting. Furthermore, the accuracy and reliability of the simulation are validated through actual coating experiments. By examining the impact of various procedural factors on the temperature distribution, it is found that optimal coating results and a tightly formed elliptical molten zone are attained at an electron beam current of 18 mA, and the scanning speed is 300 mm/min. The peak temperature in the melt pool in the coating area is 5087 K, while the lowest temperature on the isothermal in the heat-affected zone is 1409 K. Over time, there is a swift rise in temperature for the data points taken along both the X and Z trajectories, followed by rapid cooling after rapid heating. Coating experiments conducted under the optimal parameters demonstrate a dense coating layer and good bonding with the substrate, thereby validating the accuracy of the simulation. Full article
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13 pages, 5877 KiB  
Article
The Tensile Properties and Fracture Toughness of a Cast Mg-9Gd-4Y-0.5Zr Alloy
by Zhikang Ji, Xiaoguang Qiao, Shoufu Guan, Junbin Hou, Changyu Hu, Fuguan Cong, Guojun Wang and Mingyi Zheng
Crystals 2023, 13(8), 1277; https://doi.org/10.3390/cryst13081277 - 18 Aug 2023
Viewed by 796
Abstract
Low fracture toughness has been a major barrier for the structural applications of cast Mg-Gd-Y-Zr alloys. In this work, the tensile properties and fracture toughness of a direct-chill-cast Mg-9Gd-4Y-0.5Zr (VW94K) alloy were investigated in different conditions, including its as-cast and as-homogenized states. The [...] Read more.
Low fracture toughness has been a major barrier for the structural applications of cast Mg-Gd-Y-Zr alloys. In this work, the tensile properties and fracture toughness of a direct-chill-cast Mg-9Gd-4Y-0.5Zr (VW94K) alloy were investigated in different conditions, including its as-cast and as-homogenized states. The results show that the tensile properties of the as-cast VW94K alloy are greatly improved after the homogenization treatment due to the strengthening of the solid solution. The plane strain fracture toughness values KIc of the as-cast and as-homogenized VW94K alloys are 10.6 ± 0.5 and 13.8 ± 0.6 MPa·m1/2, respectively, i.e., an improvement of 30.2% in KIc is achieved via the dissolution of the Mg24(Gd, Y)5 eutectic phases. The initiation and propagation of microcracks in an interrupted fracture test are observed via an optical microscope (OM) and scanning electron microscope (SEM). The fracture surfaces of the failed samples after the fracture toughness tests are examined via an SEM. The electron backscatter diffraction (EBSD) technique is adopted to determine the failure mechanism. The results show that the microcracks are initiated and propagated across the Mg24(Gd, Y)5 eutectic compounds in the as-cast VW94K alloy. The propagation of the main cracks exhibits an intergranular fracture pattern and the whole crack propagation path displays a zigzag style. The microcracks in the as-homogenized alloy are initiated and propagated along the basal plane of the grains. The main crack in the as-homogenized alloy shows a more tortuous fracture characteristic and a trans-granular crack propagation behavior, leading to the improvement of the fracture toughness. Full article
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13 pages, 6582 KiB  
Article
In-Situ Study of Temperature- and Magnetic-Field-Induced Incomplete Martensitic Transformation in Fe-Mn-Ga
by Xiaoming Sun, Jingyi Cui, Shaofu Li, Zhiyuan Ma, Klaus-Dieter Liss, Runguang Li and Zhen Chen
Crystals 2023, 13(8), 1242; https://doi.org/10.3390/cryst13081242 - 11 Aug 2023
Viewed by 772
Abstract
Significant interest in the stoichiometric and off-stoichiometric Fe2MnGa alloys is based on their complex phase transition behavior and potential application. In this study, temperature- and magnetic-field-induced phase transformations in the Fe41.5Mn28Ga30.5 magnetic shape memory alloy were [...] Read more.
Significant interest in the stoichiometric and off-stoichiometric Fe2MnGa alloys is based on their complex phase transition behavior and potential application. In this study, temperature- and magnetic-field-induced phase transformations in the Fe41.5Mn28Ga30.5 magnetic shape memory alloy were investigated by in situ synchrotron high-energy X-ray diffraction and in situ neutron diffraction techniques. It was found that incomplete phase transformation and phase coexistence behavior are always observed while applying and removing fields in Fe41.5Mn28Ga30.5. Typically, even at 4 K and under 0 T, or increasing the magnetic field to 11 T at 250 K, it can be directly detected that the martensite and austenite are in competition, making the phase transition incomplete. TEM observations at 300 K and 150 K indicate that the anti-phase boundaries and B2 precipitates may lead to field-induced incomplete phase transformation behavior collectively. The present study may enrich the understanding of field-induced martensitic transformation in the Fe-Mn-Ga magnetic shape memory alloys. Full article
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14 pages, 4212 KiB  
Article
Study on Efficient Dephosphorization in Converter Based on Thermodynamic Calculation
by Zhong-Liang Wang, Tian-Le Song, Li-Hua Zhao and Yan-Ping Bao
Crystals 2023, 13(7), 1132; https://doi.org/10.3390/cryst13071132 - 20 Jul 2023
Viewed by 933
Abstract
Given the accelerating depletion of iron ore resources, there is growing concern within the steel industry regarding the availability of high-phosphorus iron ore. However, it is important to note that the utilization of high-phosphorus iron ore may result in elevated phosphorus content and [...] Read more.
Given the accelerating depletion of iron ore resources, there is growing concern within the steel industry regarding the availability of high-phosphorus iron ore. However, it is important to note that the utilization of high-phosphorus iron ore may result in elevated phosphorus content and notable fluctuations in molten iron, thereby imposing additional challenges on the dephosphorization process in steelmaking. The most urgent issue in the process of converter steelmaking is how to achieve efficient dephosphorization. In this study, the influence of various factors on the logarithm of the phosphorus balance distribution ratio (lgLp), the logarithm of the P2O5 activity coefficient (lgγP2O5), and the logarithm of the phosphorus capacity (lgCp) were examined through thermodynamic calculations. The impact of each factor on dephosphorization was analyzed, and the optimal conditions for the dephosphorization stage of the converter were determined. Furthermore, the influence of basicity and FetO content on the form of phosphorus in the slag was analyzed using FactSage 7.2 software, and the precipitation rules of the slag phases were explored. The thermodynamic calculation results indicated that increasing the basicity of the dephosphorization slag was beneficial for dephosphorization, but it should be maintained below 3. The best dephosphorization effect was achieved when the FetO content was around 20%. The reaction temperature during the dephosphorization stage should be kept low, as the dephosphorization efficiency decreased sharply with the increasing temperature. In dephosphorization slag, Ca3(PO4)2 usually formed a solid solution with Ca2SiO4, so the form of phosphorus in the slag was mainly determined by the precipitation form and content of Ca2SiO4. The phases in the dephosphorization slag mainly consisted of a phosphorus-rich phase, an iron-rich phase, and a matrix phase. The results of scanning electron microscopy and X-ray diffraction analyses were consistent with the thermodynamic calculation results. Full article
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19 pages, 14933 KiB  
Article
Effect of Machine Pin-Manufacturing Process Parameters by Plasma Nitriding on Microstructure and Hardness of Working Surfaces
by Włodzimierz Dudziński, Daniel Medyński and Paweł Sacher
Crystals 2023, 13(7), 1091; https://doi.org/10.3390/cryst13071091 - 13 Jul 2023
Cited by 2 | Viewed by 990
Abstract
This work concerns two stages of research into plasma nitriding (change of nitriding steel and modification of nitriding parameters). In the first stage, pins obtained from currently used steel were compared with pins made of an alternative material available on the market, using [...] Read more.
This work concerns two stages of research into plasma nitriding (change of nitriding steel and modification of nitriding parameters). In the first stage, pins obtained from currently used steel were compared with pins made of an alternative material available on the market, using the same nitriding process parameters. As a result of the metallographic tests carried out, in the first case, the presence of a thin, porous, and heterogeneous nitrided layer or its absence was found, with the core in its raw state and not thermally improved. In the second case, the presence of a nitrided layer of small thickness with noticeable porosity on the surface of the sample was found, but with a core after heat treatment (incorrect process parameters). Therefore, modification of the parameters of the nitriding process was proposed, in terms of a mixture of gases, currents, time, and temperature of the nitriding process. As a result, a satisfactory effective thickness of the nitrided layer was obtained, consisting of a white near-surface zone with ε and ε + γ′-type nitrides with a thickness of 8.7 to 10.2 µm, and a dark zone of internal nitriding with γ′ nitrides. The nitrides layer was continuous, compact, and well adhered to the steel surface. In the core of the samples, the presence of a fine-needle tempering sorbite structure with a small amount of fine bainite, which is correct for the steel after heat treatment and nitriding, was found. The most favorable parameters of the ion nitriding process were gas flow rate (1.5 L/min N; 0.4 L/min H; 0.3 L/min Ar); currents (BIAS—410 V 4.0 A, SCREEN—320 V 4.0 A); time (26 h and 35 min); and temperature (550 °C). Full article
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18 pages, 4740 KiB  
Article
Grain Size Distribution of DP 600 Steel Using Single-Pass Asymmetrical Wedge Test
by Urška Klančnik, Peter Fajfar, Jan Foder, Heinz Palkowski, Jaka Burja and Grega Klančnik
Crystals 2023, 13(7), 1055; https://doi.org/10.3390/cryst13071055 - 04 Jul 2023
Viewed by 1002
Abstract
Grain size distribution after the completion of a phase transformation was studied through the laboratory-controlled hot-plastic deformation of dual phase 600 (DP 600) steel using a specially prepared asymmetric single-pass hot-rolling wedge test with a refined reheating grain size instead of the usual [...] Read more.
Grain size distribution after the completion of a phase transformation was studied through the laboratory-controlled hot-plastic deformation of dual phase 600 (DP 600) steel using a specially prepared asymmetric single-pass hot-rolling wedge test with a refined reheating grain size instead of the usual coarse-grained starting microstructure observed in practice. The experiment was performed to reduce generally needed experimental trials to observe the microstructure development at elevated temperatures, where stable and unstable conditions could be observed as in the industrial hot-rolling practice. For this purpose, experimental stress–strain curves and softening behaviors were used concerning FEM simulations to reproduce in situ hot-rolling conditions to interpret the grain size distribution. The presented study revealed that the usual approach found in the literature for microstructure investigation and evolution with a hot-rolling wedge test was deficient concerning the observed field of interest. The degree of potential error concerning the implemented deformation per notch position, as well as the stress–strain rate and related mean flow stresses, were highly related to the geometry of the specimen and the material behavior itself, which could be defined by the actual hardening and softening kinetics (recrystallization and grain growth at elevated temperatures and longer interpass times). The grain size distribution at 1100–1070 °C was observed up to a 3.45 s−1 strain rate and, based on its stable forming behavior according to the FEM simulations and the optimal refined grain size, the optimal deformation was positioned between e = 0.2 and e = 0.5. Full article
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12 pages, 3629 KiB  
Article
Detection of Porosity in Impregnated Die-Cast Aluminum Alloy Piece by Metallography and Computer Tomography
by Mihály Réger, József Gáti, Ferenc Oláh, Richárd Horváth, Enikő Réka Fábián and Tamás Bubonyi
Crystals 2023, 13(7), 1014; https://doi.org/10.3390/cryst13071014 - 26 Jun 2023
Cited by 2 | Viewed by 1755
Abstract
The porosity of die-cast aluminum alloys is a determining factor for the quality of the product. In this paper, we studied the porosity of a selected part of a die-cast AlSi9Cu3(Fe) compressor part by computer tomography and metallography. In the case of this [...] Read more.
The porosity of die-cast aluminum alloys is a determining factor for the quality of the product. In this paper, we studied the porosity of a selected part of a die-cast AlSi9Cu3(Fe) compressor part by computer tomography and metallography. In the case of this part, the achievable resolution by CT, a non-destructive testing method, was 30 μm—this method could not detect smaller cavities. Based on metallographic analysis, the percentage of defects larger than 30 μm ranges from 10 to 30% of the total number of defects, which represents 75–95% of the defective area (area ratio). Impregnation with methacrylate resin (used to seal cavities to prevent leakage) can be detected with UV-illuminated optical microscopic examination on metallographically prepared specimens. As confirmed by scanning electron microscopy, partial filling and partial impregnation can occur in a system of shrinkage cavities. Full article
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13 pages, 4553 KiB  
Article
Effect of Aging Temperature on Precipitates Evolution and Mechanical Properties of GH4169 Superalloy
by Anqi Liu, Fei Zhao, Wensen Huang, Yuanbiao Tan, Yonghai Ren, Longxiang Wang and Fahong Xu
Crystals 2023, 13(6), 964; https://doi.org/10.3390/cryst13060964 - 17 Jun 2023
Cited by 1 | Viewed by 921
Abstract
GH4169 is primarily strengthened through precipitation, with heat treatment serving as a crucial method for regulating the precipitates of the alloy. However, the impact of aging temperature on the microstructure and properties of GH4169 has not been thoroughly studied, hindering effective regulation of [...] Read more.
GH4169 is primarily strengthened through precipitation, with heat treatment serving as a crucial method for regulating the precipitates of the alloy. However, the impact of aging temperature on the microstructure and properties of GH4169 has not been thoroughly studied, hindering effective regulation of its microstructure and properties. This study systematically investigated the effects of aging temperature on the evolution of precipitates and mechanical properties of GH4169 alloy using various techniques such as OM, SEM, XRD and TEM. The results indicate that raising the aging temperature leads to an increase in the sizes of both the γ″ and γ′ phases in the alloy, as well as promoting the precipitation of δ phase at grain boundaries. Notably, the increase in γ″ phase size enhances the strength of the alloy, while the presence of δ phase is detrimental to its strength but greatly enhances its elongation. The yield strength of the alloy aged at 750 ℃ exhibits the highest yield strength, with values of 1135 MPa and 1050 MPa at room temperature and elevated temperature, respectively. As the aging temperature increases, the Portevin-Le Châtelier (PLC) effect during elevated temperature tensile tests at 650 ℃ gradually weakens. The PLC effect disappears almost completely when the aging temperature reaches 780 ℃. Full article
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12 pages, 2045 KiB  
Article
Investigation on Structural, Tensile Properties and Electronic of Mg–X (X = Zn, Ag) Alloys by the First-Principles Method
by Yan Gao, Wenjiang Feng, Chuang Wu, Lu Feng and Xiuyan Chen
Crystals 2023, 13(5), 820; https://doi.org/10.3390/cryst13050820 - 16 May 2023
Viewed by 904
Abstract
In order to study the strengthening effect of Mg–X (X = Zn, Ag) alloys, solid solution structures of Mg54, Mg53X1 and Mg52X2 (X = Zn, Ag) with atomic contents of 1.8 at.% and 3.7 at.% [...] Read more.
In order to study the strengthening effect of Mg–X (X = Zn, Ag) alloys, solid solution structures of Mg54, Mg53X1 and Mg52X2 (X = Zn, Ag) with atomic contents of 1.8 at.% and 3.7 at.% were established, respectively. The structural stability, tensile properties and electronic properties were investigated by first-principles simulation. The calculated results of cohesive energies show that all solid solution structures were stable under different tensile strains, and Mg52Ag2 had the best stability. The results of tensile tests show that Zn and Ag atoms promoted the Mg-based alloy’s yield strength and tensile strength. In addition, through comparative analyses, we have demonstrated that the tensile property of Mg-based alloys was also affected by solid solubility. Finally, the electronic density of states (DOS) and electron density difference of several solid solution structures were analyzed. Full article
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11 pages, 3364 KiB  
Article
Thermal-Mechanical Fatigue Behavior and Life Assessment of Single Crystal Nickel-Based Superalloy
by Juan Cao, Fulei Jing and Junjie Yang
Crystals 2023, 13(5), 780; https://doi.org/10.3390/cryst13050780 - 08 May 2023
Cited by 1 | Viewed by 1106
Abstract
Thermal-mechanical fatigue (TMF) tests and isothermal fatigue (IF) tests were conducted using thin-walled tubular specimens under strain-controlled conditions. The results of TMF tests showed a strong correlation between mechanical behavior and temperature cycling. Under different phases of temperature and mechanical loading, the hysteresis [...] Read more.
Thermal-mechanical fatigue (TMF) tests and isothermal fatigue (IF) tests were conducted using thin-walled tubular specimens under strain-controlled conditions. The results of TMF tests showed a strong correlation between mechanical behavior and temperature cycling. Under different phases of temperature and mechanical loading, the hysteresis loop and mean stress of the single crystal superalloy showed noticeable variations between the stress-controlled and strain-controlled conditions. In the strain-controlled TMF test, temperature cycling led to stress asymmetry and additional damage, resulting in a significantly lower TMF life compared to IF life at the maximum temperature. Moreover, the OP TMF life is generally lower than that of the IP TMF at the same strain amplitude. The Walker viscoplastic constitutive model based on slip systems was used to analyze the TMF mechanical behavior of the single crystal superalloy, and the change trends of the maximum Schmid stress, the maximum slip shear strain rate, and the slip shear strain range were analyzed, and their relationship with the TMF life was investigated. Finally, a TMF life prediction model independent of the loading mode and phase was constructed based on meso-mechanical damage parameters. The predicted TMF lives for different load control modes and phases fell within the twofold dispersion band. Full article
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14 pages, 4983 KiB  
Article
Friction and Wear Behavior of NM500 Wear-Resistant Steel in Different Environmental Media
by Guobo Wang, Hao Zhao, Yu Zhang, Jie Wang, Guanghui Zhao and Lifeng Ma
Crystals 2023, 13(5), 770; https://doi.org/10.3390/cryst13050770 - 05 May 2023
Cited by 4 | Viewed by 1091
Abstract
The study aims to investigate the influence of environmental media on the friction and wear behavior of low-alloy wear-resistant steels and to provide practical references for their application. This article conducted sliding wear tests on NM500 wear-resistant steel under different loads under air [...] Read more.
The study aims to investigate the influence of environmental media on the friction and wear behavior of low-alloy wear-resistant steels and to provide practical references for their application. This article conducted sliding wear tests on NM500 wear-resistant steel under different loads under air atmosphere, deionized water, and 3.5 wt% NaCl solution conditions. Someone quantitatively measured the friction coefficient and wear amount of each friction pair. The present study employed scanning electron microscopy, energy dispersive spectroscopy, and a white light interference three-dimensional surface profiler to analyze the surface structure, cross-sectional morphology, element distribution, and wear mechanism of the wear scars under various experimental conditions. The results show that: In deionized water, NM500 has the best wear resistance, while the dry state is the worst. The lubricating and cooling effect of the liquid, as well as the corrosive effect of the NaCl solution, play an essential role in the wear behavior of NM500. Under dry friction conditions, the wear mechanism of NM500 is principally adhesive wear, fatigue wear, and oxidation wear. In the case of wear testing in deionized water, the researchers characterized the dominant wear mechanism as adhesive wear in conjunction with fatigue wear and abrasive wear. In contrast, when they carried out the wear testing in NaCl solution, the wear mechanism was primarily driven by corrosion wear and adhesive wear, with only a minor contribution from fatigue wear. Full article
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15 pages, 65045 KiB  
Article
Plasma-Pulsed GMAW Hybrid Welding Process of 6061 Aluminum and Zinc-Coated Steel
by Hongchang Zhang, Wenhu He, Huaibei Zheng, Jiang Yu, Hongtao Zhang, Yinan Li, Jianguo Gao and Zhaofang Su
Crystals 2023, 13(5), 723; https://doi.org/10.3390/cryst13050723 - 25 Apr 2023
Viewed by 969
Abstract
A novel plasma-pulsed GMAW hybrid welding (plasma-GMAW-P) process is proposed for joining 6061 aluminum and zinc-coated steel. The results show that the change in welding heat input has little effect on the microstructure of the joint and the composition of the intermetallic compounds [...] Read more.
A novel plasma-pulsed GMAW hybrid welding (plasma-GMAW-P) process is proposed for joining 6061 aluminum and zinc-coated steel. The results show that the change in welding heat input has little effect on the microstructure of the joint and the composition of the intermetallic compounds (IMCs) but only changes the thickness of the reaction layer (increased from 5 μm to 12 μm). when the plasma arc current is 20 A and the MIG current is 80 A, the welded joint obtained has the highest tensile-shear force. With the optimal process parameters, the weld strength obtained by filling ER4043 welding wire is the highest, accounting for 65% of the tensile-shear force of the base material. The effect of the plasma arc acting on the joint properties is studied through the microstructure and a tensile-shearing test. The action position of the plasma arc plays a significant role in the Al/steel interface, which directly influences the strength of the welded joints. Regardless of the plasma-GMAW-P style used to obtain the joints, Fe-Al IMCs appear at the interface. When the plasma arc is in front of the welding direction and the GMAW-P arc is in the rear, the tensile-shear force reaches the maximum of 3322 N. Full article
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12 pages, 4724 KiB  
Article
Phase Transition of Nb3Sn during the Heat Treatment of Precursors after Mechanical Alloying
by Wanshuo Sun and Shunzhong Chen
Crystals 2023, 13(4), 660; https://doi.org/10.3390/cryst13040660 - 11 Apr 2023
Viewed by 1130
Abstract
The phase transition process of Nb3Sn during heat treatment exerts important influences on Nb3Sn formation and the superconducting characteristics of Nb3Sn superconductors. A simple method for quickly preparing Nb3Sn was studied. First, Nb, Sn, and [...] Read more.
The phase transition process of Nb3Sn during heat treatment exerts important influences on Nb3Sn formation and the superconducting characteristics of Nb3Sn superconductors. A simple method for quickly preparing Nb3Sn was studied. First, Nb, Sn, and Cu powders were mechanically alloyed to prepare the precursor. Then, the precursor was heat treated at different times to form Nb3Sn. During the first stage, the morphology and crystal structure of the products were analyzed after different milling times. The results of the transmission electron microscopy showed the poor crystallinity of the products compared with the original materials. During the second stage, heat treatment was performed at different temperatures ranging from room temperature to 1073 K. After treatment, the products were studied via X-ray diffraction analysis to determine how the structure changed with increasing temperature. Only the Nb diffraction peaks in the precursor were observed after high-energy ball milling for more than 3 h. When the heat treatment temperature was above 773 K and heat treatment time was 15 min, Nb3Sn began to form. When the temperature was above 973 K, some impurities, such as Nb2O5, appeared. After 5 h of ball milling, the precursor was heat treated at different times in a vacuum heat treatment furnace. The crystal structure of the product exhibited evident diffraction peaks of Nb3Sn. The critical temperatures of the samples that were heat treated at different times were between 17 K and 18 K. The magnetic critical current density of the sample versus the applied magnetic field at 4.2 K indicated that the magnetic Jc was approximately 30,000 A/cm2. Full article
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12 pages, 21057 KiB  
Article
Precipitation of Topologically Closed Packed Phases during the Heat-Treatment of Rhenium Containing Single Crystal Ni-Based Superalloys
by John Harrison and Paul A. Withey
Crystals 2023, 13(3), 519; https://doi.org/10.3390/cryst13030519 - 17 Mar 2023
Cited by 2 | Viewed by 1142
Abstract
Continual development of nickel-based superalloys for single-crystal turbine applications has pushed their operating temperatures higher and higher, most notably through the addition of rhenium. However, this has left them susceptible to the precipitation of topologically closed packed phases (TCPs), which are widely considered [...] Read more.
Continual development of nickel-based superalloys for single-crystal turbine applications has pushed their operating temperatures higher and higher, most notably through the addition of rhenium. However, this has left them susceptible to the precipitation of topologically closed packed phases (TCPs), which are widely considered detrimental. Whilst these have long been reported as an end-of-life phenomenon in in-service components, they have more recently been observed during the manufacture of turbine blades. Several rhenium-containing alloys (CMSX-4, CMSX-10K, and CMSX-10N) were cast into single-crystal test bars and studied at different times along their solution heat-treatment process to discern if, when, and where these TCPs precipitated. It was seen that all alloys were susceptible to TCPs at some point along the process, with the higher rhenium-containing alloy CMSX-10N being the most prone. They occurred at the earliest stages of the solution process; this was attributed to aluminium diffusion from the segregated interdendritic regions into the dendrite core, causing the concentration of rhenium into the ɣ-matrixes until sufficient potential was achieved for TCP precipitation. As the samples became more homogeneous, fewer TCPs were observed; however, in the case of CMSX-10N, this took longer than the typical 24-h solution time used in industry, leading to components entering service with TCPs still present. Full article
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11 pages, 11237 KiB  
Article
Research on the Microstructure and Properties of a Flux-Cored Wire Gas-Shielded Welded Joint of A710 Low-Alloy High-Strength Steel
by Xing Wang, Zhibin Yang and Lingzhi Du
Crystals 2023, 13(3), 484; https://doi.org/10.3390/cryst13030484 - 11 Mar 2023
Cited by 1 | Viewed by 1267
Abstract
In this study, a 16 mm thick A710 low-alloy high-strength steel was welded by using flux-cored wire gas-shielded welding with an E81T1-Ni1M flux-cored wire. The microstructure characteristics and mechanical properties of the joints were systematically studied. The results showed that the joint was [...] Read more.
In this study, a 16 mm thick A710 low-alloy high-strength steel was welded by using flux-cored wire gas-shielded welding with an E81T1-Ni1M flux-cored wire. The microstructure characteristics and mechanical properties of the joints were systematically studied. The results showed that the joint was well formed without obvious welding defects. The center of the weld was mainly needle-like ferrite, the coarse grain area was mainly slat-like and granular bainite, and the fine grain area was mainly ferrite and pearlite. The lowest hardness in the weld area was the weakest area of the joint. The average tensile strength of the joint was 650 MPa, reaching 95% of the base metal; the samples were all fractured in the weld area, and the fracture morphology showed typical plastic fracture characteristics. The low-temperature (−40 °C) impact energy of the joint weld area and the heat-affected zone were 71 J and 253 J; the fracture morphology was characterized by a ductile–brittle mixed fracture, and the ductile area of the specimen fracture in the heat-affected zone was larger. The bending performance was good. Under the specified life of 2 × 106 cycles; the median fatigue limit and the safety fatigue limit were 520 MPa and 492 MPa, and the fatigue cracks germinated on the surface of the priming weld. Full article
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12 pages, 8426 KiB  
Article
A Study on the Co-Content Optimization of the DD15 Single-Crystal Superalloy
by Zhenxue Shi and Shizhong Liu
Crystals 2023, 13(3), 389; https://doi.org/10.3390/cryst13030389 - 24 Feb 2023
Cited by 1 | Viewed by 876
Abstract
The fourth-generation single-crystal superalloy DD15 with 6% Co, 9% Co and 12% Co was cast using the vacuum directionally solidified furnace, while other alloying element’s content remained unchanged. The long-term aging experiment was conducted at 1100 °C for 1000 h after standard heat [...] Read more.
The fourth-generation single-crystal superalloy DD15 with 6% Co, 9% Co and 12% Co was cast using the vacuum directionally solidified furnace, while other alloying element’s content remained unchanged. The long-term aging experiment was conducted at 1100 °C for 1000 h after standard heat treatment. The stress rupture tests of the alloy were conducted at 1100 °C/137 MPa and 1140 °C/137 Mpa. The influence of Co content on the microstructure and stress rupture properties of DD15 alloy had been investigated to optimize the Co content to obtain excellent comprehensive performance. The results showed that the primary dendrite arm spacing of the alloy decreases at first and increases afterwards, and the volume fraction of γ-γ′ eutectic decreases with the growth of Co content in the as-cast microstructures. The size, cubic degree and volume fraction of the γ′ phase of the alloy after standard heat treatment all decrease with the increase in Co content. The microstructure stability of the alloy is enhanced with the increase in Co content. No TCP phase was present in the alloy with 12% Co precipitate even after aging 1000 h. The stress rupture lives at two conditions, both reduced in different degrees with the increase in Co content. The effect of Co on the stress rupture life of the alloy improves with the increase in Co content or test temperature. The acicular TCP phase appeared in the 6% Co alloy and 9% Co alloy in the microstructure of the ruptured specimens with different Co contents. Moreover, the TCP phase content in the 6% Co alloy is much more than that in the 9% Co alloy. There is no TCP phase precipitation in the 12% Co alloy. At last, the relationship between microstructure stability, stress rupture properties and Co content of the alloy is discussed. The alloy containing 9% Co is the best choice considering the microstructure stability and stress rupture properties. Full article
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