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Light Alloys and High-Temperature Alloys

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Metals and Alloys".

Deadline for manuscript submissions: closed (20 August 2022) | Viewed by 29990

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Guest Editor
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China
Interests: light alloys (Al-, Mg-); Ni-based super alloys; high-entropy alloys; CALPHAD; phase-field modeling; machine learning; alloy design
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Special Issue Information

Dear Colleagues,

Light alloys (Al-, Mg-, and Ti-based) and high-temperature alloys are widely used as key engineering materials in both civil and military industries due to their excellent comprehensive properties and performance. In order to meet the growing demand on the properties/performance of the materials, there is a perpetual need to explore novel light and high-temperature alloys. In this Special Issue of Materials, I would like to call for submission of papers on any new progress/development in the fields of light and high-temperature alloys. Both research and review articles are welcomed.

This Special Issue majorly covers all the theoretical and experimental investigations into different types of light alloys, including Al-, Mg-, and Ti-based, and high-temperature alloys, including Ni-, Co-, Fe-, and Nb-based. Either the mechanical or functional behaviors at all length scales can be emphasized. Related topics, like the protective coatings on high-temperature alloys, metal matrix composites, and so on, also fall within the scope of this Special Issue. Moreover, research on the new type of high-temperature alloys, i.e., high-entropy alloys, or multi-principal element alloys, are welcomed as well.

The deadline for all the submissions is 30 November 2021.

Thank you very much, and I look forward to receiving your submission soon!

Prof. Dr. Lijun Zhang
Guest Editor

Manuscript Submission Information

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Keywords

  • light alloys (Al-, Mg-, and Ti-based)
  • high-temperature alloys (Ni-, Co-, Fe-, and Nb-based)
  • high-entropy alloys
  • light/high-temperature alloy-based composites
  • microstructure
  • mechanical properties
  • corrosion and oxidation
  • phase equilibrium and diffusion
  • alloy design
  • integrated computational materials engineering

Published Papers (14 papers)

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Research

16 pages, 7472 KiB  
Article
High-Throughput Computing Assisted by Knowledge Graph to Study the Correlation between Microstructure and Mechanical Properties of 6XXX Aluminum Alloy
by Xiaoyu Zheng, Yi Kong, Tingting Chang, Xin Liao, Yiwu Ma and Yong Du
Materials 2022, 15(15), 5296; https://doi.org/10.3390/ma15155296 - 1 Aug 2022
Cited by 4 | Viewed by 1716
Abstract
It is of great academic and engineering application to study the evolution of microstructure and properties of age-strengthened aluminum alloys during heat treatment and to establish quantitative prediction models that can be applied to industrial production. The main factors affecting the peak aging [...] Read more.
It is of great academic and engineering application to study the evolution of microstructure and properties of age-strengthened aluminum alloys during heat treatment and to establish quantitative prediction models that can be applied to industrial production. The main factors affecting the peak aging state strength of age-strengthened aluminum alloys are the precipitates, solid solution elements, grain size effects, and textures formed during the material processing. In this work, these multi-scale factors are integrated into the framework of the knowledge graph to assist the following crystal plasticity finite elements simulations. The constructed knowledge graph is divided into two parts: static data and dynamic data. Static data contains the basic properties of the material and the most basic property parameters. Dynamic data is designed to improve awareness of static data. High-throughput computing is performed to further obtain clear microstructure-property relationships by varying the parameters of materials properties and the characteristics of the structure models. The constructed knowledge graph can be used to guide material design for 6XXX Al-Mg-Si based alloys. The past experimental values are used to calibrate the phenomenological parameters and test the reliability of the analysis process. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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14 pages, 7581 KiB  
Article
X-ray Thermo-Diffraction Study of the Aluminum-Based Multicomponent Alloy Al58Zn28Si8Mg6
by Yoana Bilbao, Juan José Trujillo, Iban Vicario, Gurutze Arruebarrena, Iñaki Hurtado and Teresa Guraya
Materials 2022, 15(14), 5056; https://doi.org/10.3390/ma15145056 - 20 Jul 2022
Cited by 2 | Viewed by 1546
Abstract
Newly designed multicomponent light alloys are giving rise to non-conventional microstructures that need to be thoroughly studied before determining their potential applications. In this study, the novel Al58Zn28Si8Mg6 alloy, previously studied with CALPHAD methods, was cast [...] Read more.
Newly designed multicomponent light alloys are giving rise to non-conventional microstructures that need to be thoroughly studied before determining their potential applications. In this study, the novel Al58Zn28Si8Mg6 alloy, previously studied with CALPHAD methods, was cast and heat-treated under several conditions. An analysis of the phase evolution was carried out with in situ X-ray diffraction supported by differential scanning calorimetry and electron microscopy. A total of eight phases were identified in the alloy in the temperature range from 30 to 380 °C: α-Al, α’-Al, Zn, Si, Mg2Si, MgZn2, Mg2Zn11, and SrZn13. Several thermal transitions below 360 °C were determined, and the natural precipitation of the Zn phase was confirmed after nine months. The study showed that the thermal history can strongly affect the presence of the MgZn2 and Mg2Zn11 phases. The combination of X-ray thermo-diffraction with CALPHAD methods, differential scanning calorimetry, and electron microscopy offered us a satisfactory understanding of the alloy behavior at different temperatures. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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15 pages, 9917 KiB  
Article
Microstructures and Mechanical Properties of H13 Tool Steel Fabricated by Selective Laser Melting
by Fei Lei, Tao Wen, Feipeng Yang, Jianying Wang, Junwei Fu, Hailin Yang, Jiong Wang, Jianming Ruan and Shouxun Ji
Materials 2022, 15(7), 2686; https://doi.org/10.3390/ma15072686 - 6 Apr 2022
Cited by 14 | Viewed by 3352
Abstract
H13 stool steel processed by selective laser melting (SLM) suffered from severe brittleness and scatter distribution of mechanical properties. We optimized the mechanical response of as-SLMed H13 by tailoring the optimisation of process parameters and established the correlation between microstructure and mechanical properties [...] Read more.
H13 stool steel processed by selective laser melting (SLM) suffered from severe brittleness and scatter distribution of mechanical properties. We optimized the mechanical response of as-SLMed H13 by tailoring the optimisation of process parameters and established the correlation between microstructure and mechanical properties in this work. Microstructures were examined using XRD, SEM, EBSD and TEM. The results showed that the microstructures were predominantly featured by cellular structures and columnar grains, which consisted of lath martensite and retained austenite with numerous nanoscale carbides being distributed at and within sub-grain boundaries. The average size of cellular structure was ~500 nm and Cr and Mo element were enriched toward the cell wall of each cellular structure. The as-SLMed H13 offered the yield strength (YS) of 1468 MPa, the ultimate tensile strength (UTS) of 1837 MPa and the fracture strain of 8.48%. The excellent strength-ductility synergy can be attributed to the refined hierarchical microstructures with fine grains, the unique cellular structures and the presence of dislocations. In addition, the enrichment of solute elements along cellular walls and carbides at sub-grain boundaries improve the grain boundary strengthening. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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13 pages, 2117 KiB  
Article
Third-Generation Thermodynamic Descriptions for Ta-Cr and Ta-V Binary Systems
by Enkuan Zhang, Xinpei Xu, Yun Chen and Ying Tang
Materials 2022, 15(6), 2074; https://doi.org/10.3390/ma15062074 - 11 Mar 2022
Cited by 1 | Viewed by 2122
Abstract
The third-generation thermodynamic descriptions for Ta-Cr and Ta-V binary systems were performed to construct the reliable thermodynamic database for refractory high-entropy alloys (RHEAs) containing Laves phase. The third-generation Gibbs energy expressions of pure Cr and V in both solid and liquid phases were [...] Read more.
The third-generation thermodynamic descriptions for Ta-Cr and Ta-V binary systems were performed to construct the reliable thermodynamic database for refractory high-entropy alloys (RHEAs) containing Laves phase. The third-generation Gibbs energy expressions of pure Cr and V in both solid and liquid phases were established, from which the thermodynamic properties and thermal vacancy can be well described. The thermodynamic descriptions of Ta-Cr and Ta-V over the whole composition and temperature regions were carried out based on the reviewed phase equilibria and thermodynamic data with the CALPHAD (CALculation of PHAse Diagrams) approach. Specifically, the thermodynamic parameters of C14 and C15 Laves phases were evaluated by combining the theoretically computed and experimentally measured thermodynamic properties as well as the semiempirical relations. The calculated phase diagrams and thermodynamic properties in Ta-Cr and Ta-V systems according to the present thermodynamic parameters had a nice agreement with the experimental data even down to 0 K, indicating the reliability of the present modeling. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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19 pages, 9532 KiB  
Article
An Effective Strategy to Maintain the CALPHAD Atomic Mobility Database of Multicomponent Systems and Its Application to Hcp Mg–Al–Zn–Sn Alloys
by Ting Cheng, Jing Zhong and Lijun Zhang
Materials 2022, 15(1), 283; https://doi.org/10.3390/ma15010283 - 31 Dec 2021
Cited by 2 | Viewed by 1899
Abstract
In this paper, a general and effective strategy was first developed to maintain the CALPHAD atomic mobility database of multicomponent systems, based on the pragmatic numerical method and freely accessible HitDIC software, and then applied to update the atomic mobility descriptions of the [...] Read more.
In this paper, a general and effective strategy was first developed to maintain the CALPHAD atomic mobility database of multicomponent systems, based on the pragmatic numerical method and freely accessible HitDIC software, and then applied to update the atomic mobility descriptions of the hcp Mg–Al–Zn, Mg–Al–Sn, and Mg–Al–Zn–Sn systems. A set of the self-consistent atomic mobility database of the hcp Mg–Al–Zn–Sn system was established following the new strategy presented. A comprehensive comparison between the model-predicted composition–distance profiles/inter-diffusivities in the hcp Mg–Al–Zn, Mg–Al–Sn, and Mg–Al–Zn–Sn systems from the presently updated atomic mobilities and those from the previous ones that used the traditional method indicated that significant improvement can be achieved utilizing the new strategy, especially in the cases with sufficient experimental composition–distance profiles and/or in higher-order systems. Furthermore, it is anticipated that the proposed strategy can serve as a standard for maintaining the CALPHAD atomic mobility database in different multicomponent systems. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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10 pages, 3537 KiB  
Article
Nb/Sn Liquid-Solid Reactive Diffusion Couples and Their Application to Determination of Phase Equilibria and Interdiffusion Coefficients of Nb-Sn Binary System
by Jiali Zhang, Jing Zhong, Qin Li and Lijun Zhang
Materials 2022, 15(1), 113; https://doi.org/10.3390/ma15010113 - 24 Dec 2021
Cited by 1 | Viewed by 2201
Abstract
Nb3Sn plays an irreplaceable role in superconducting parts due to its stable performance under high field conditions. Accurate phase equilibria and interdiffusion coefficients are of great significance for designing novel Nb3Sn superconductors. However, the related experimental information is still [...] Read more.
Nb3Sn plays an irreplaceable role in superconducting parts due to its stable performance under high field conditions. Accurate phase equilibria and interdiffusion coefficients are of great significance for designing novel Nb3Sn superconductors. However, the related experimental information is still in a state of scarcity because of the difficulty in fabrication of Nb-Sn alloys caused by the large difference in melting points of Nb and Sn. In this paper, a simple but pragmatic approach was first proposed to prepare the Nb/Sn liquid-solid reactive diffusion couples (LSDCs) at 1100 °C and 1200 °C, of which the phase identification of the formed layer and the measurement of composition-distance profiles were conducted. The formed layer in Nb/Sn LSDCs was confirmed to be Nb3Sn compound. While the measured composition profiles were employed to determine the phase equilibria according to the local equilibrium hypothesis and the interdiffusion coefficients with an aid of the latest version of HitDIC software. The determined phase equilibria of Nb3Sn, (Nb) and liquid show good agreement with the assessed phase diagram. While the calculated interdiffusion coefficients and activation energy for diffusion in Nb3Sn are consistent with both experimental and theoretical data in the literature. Moreover, the growth of the formed Nb3Sn layer in Nb/Sn LSDCs was also found to be diffusion controlled. All the obtained phase equilibria and interdiffusion coefficients are of great value for further thermodynamic and kinetic modeling of the Nb-Sn system. Furthermore, it is anticipated that the presently proposed approach of fabricating liquid-solid reactive diffusion couple should serve as a general one for various alloy systems with large differences in melting points. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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16 pages, 5780 KiB  
Article
A First-Principles Study of the Cu-Containing β″ Precipitates in Al-Mg-Si-Cu Alloy
by Shaozhi He, Jiong Wang, Donglan Zhang, Qing Wu, Yi Kong and Yong Du
Materials 2021, 14(24), 7879; https://doi.org/10.3390/ma14247879 - 19 Dec 2021
Cited by 4 | Viewed by 2654
Abstract
The nanostructured β″ precipitates are critical for the strength of Al-Mg-Si-(Cu) aluminum alloys. However, there are still controversial reports about the composition of Cu-containing β″ phases. In this work, first-principles calculations based on density functional theory were used to investigate the composition, mechanical [...] Read more.
The nanostructured β″ precipitates are critical for the strength of Al-Mg-Si-(Cu) aluminum alloys. However, there are still controversial reports about the composition of Cu-containing β″ phases. In this work, first-principles calculations based on density functional theory were used to investigate the composition, mechanical properties, and electronic structure of Cu-containing β″ phases. The results predict that the Cu-containing β″ precipitates with a stoichiometry of Mg4+xAl2−xCuSi4 (x = 0, 1) are energetically favorable. As the concentration of Cu atoms increases, Cu-containing β″ phases with different compositions will appear, such as Mg4AlCu2Si4 and Mg4Cu3Si4. The replacement order of Cu atoms in β″ phases can be summarized as one Si3/Al site → two Si3/Al sites → two Si3/Al sites and one Mg1 site. The calculated elastic constants of the considered β″ phases suggest that they are all mechanically stable, and all β″ phases are ductile. When Cu atoms replace Al atoms at Si3/Al sites in β″ phases, the values of bulk modulus (B), shear modulus (G), and Young’s modulus (E) all increase. The calculation of the phonon spectrum shows that Mg4+xAl2−xCuSi4 (x = 0, 1) are also dynamically stable. The electronic structure analysis shows that the bond between the Si atom and the Cu atom has a covalent like property. The incorporation of the Cu atom enhances the electron interaction between the Mg2 and the Si3 atom so that the Mg2 atom also joins the Si network, which may be one of the reasons why Cu atoms increase the structure stability of the β″ phases. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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10 pages, 3598 KiB  
Article
Experimental Investigation and Thermodynamic Verification for the Phase Relation around the ε-Mg23 (Al, Zn)30 Intermetallic Compound in the Mg-Zn-Al System
by Yan Zheng, Jiaxing Sun, Kaiming Cheng, Jin Wang, Chengwei Zhan, Jingrui Zhao, Xitao Wang, Shouqiu Tang, Jixue Zhou, Lijun Zhang and Yong Du
Materials 2021, 14(22), 6892; https://doi.org/10.3390/ma14226892 - 15 Nov 2021
Cited by 2 | Viewed by 1481
Abstract
The appearance of the ε phase during the welding process can severely weaken the welding strength of dissimilar metals of Mg-Zn-Al alloy systems. An understanding of the accurate phase diagram, especially the equilibrium phase relation around the ε phase, is thus of particular [...] Read more.
The appearance of the ε phase during the welding process can severely weaken the welding strength of dissimilar metals of Mg-Zn-Al alloy systems. An understanding of the accurate phase diagram, especially the equilibrium phase relation around the ε phase, is thus of particular importance. However, the phase interrelation near the ε-Mg23(Al, Zn)30 phase has not yet been fully studied. In this work, the local phase diagrams of the ε phase and its surrounding phases in the Mg-Zn-Al system are systematically determined by experimental investigation and thermodynamic verification. Five Mg-Zn-Al alloys and one diffusion couple were fabricated and analyzed to get accurate phase constituents and relationships adjacent to ε phase. The current experimental data obtained from Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Electron Probe Micro Analysis (EPMA) were further compared with the thermodynamically computed phase relations around ε phase for verification, showing good agreements. Several important conclusions are drawn based on current experimental work, which can provide supporting information for the follow-up studies on ε phase in the Mg-Zn-Al alloy systems. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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35 pages, 19621 KiB  
Article
Mechanical Behavior of Titanium Based Metal Matrix Composites Reinforced with TiC or TiB Particles under Quasi-Static and High Strain-Rate Compression
by Pavlo E. Markovsky, Jacek Janiszewski, Oleksandr O. Stasyuk, Vadim I. Bondarchuk, Dmytro G. Savvakin, Kamil Cieplak, Daniel Goran, Purvesh Soni and Sergey V. Prikhodko
Materials 2021, 14(22), 6837; https://doi.org/10.3390/ma14226837 - 12 Nov 2021
Cited by 7 | Viewed by 2107
Abstract
The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s−1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent [...] Read more.
The mechanical behavior of titanium alloys has been mostly studied in quasi-static conditions when the strain rate does not exceed 10 s−1, while the studies performed in dynamic settings specifically for Ti-based composites are limited. Such data are critical to prevent the “strength margin” approach, which is used to assure the part performance under dynamic conditions in the absence of relevant data. The purpose of this study was to obtain data on the mechanical behavior of Ti-based composites under dynamic condition. The Metal Matrix Composites (MMC) on the base of the alloy Ti-6Al-4V (wt.%) were made using Blended Elemental Powder Metallurgy with different amounts of reinforcing particles: 5, 10, and 20% of TiC or 5, 10% (vol.) of TiB. Composites were studied at high strain rate compression ~1–3 × 103·s−1 using the split Hopkinson pressure bar. Mechanical behavior was analyzed considering strain rate, phase composition, microstructure, and strain energy (SE). It is shown that for the strain rates up to 1920 s−1, the strength and SE of MMC with 5% TiC are substantially higher compared to particles free alloy. The particles TiC localize the plastic deformation at the micro level, and fracturing occurs mainly by crushing particles and their aggregates. TiB MMCs have a finer grain structure and different mechanical behavior. MMC with 5 and 10% TiB do not break down at strain rates up to almost 3000 s−1; and 10% MMC surpasses other materials in the SE at strain rates exceeding 2200 s−1. The deformation mechanism of MMCs was evaluated. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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22 pages, 12959 KiB  
Article
Modeling and Characterization of Complex Concentrated Alloys with Reduced Content of Critical Raw Materials
by Beatrice-Adriana Șerban, Ioana-Cristina Badea, Nicolae Constantin, Dumitru Mitrică, Mihai Tudor Olaru, Marian Burada, Ioana Anasiei, Simona-Elena Bejan, Andreea-Nicoleta Ghiță and Ana Maria-Julieta Popescu
Materials 2021, 14(18), 5263; https://doi.org/10.3390/ma14185263 - 13 Sep 2021
Cited by 2 | Viewed by 1622
Abstract
The continuous development of society has increased the demand for critical raw materials (CRMs) by using them in different industrial applications. Since 2010, the European Commission has compiled a list of CRMs and potential consumption scenarios with significant economic and environmental impacts. Various [...] Read more.
The continuous development of society has increased the demand for critical raw materials (CRMs) by using them in different industrial applications. Since 2010, the European Commission has compiled a list of CRMs and potential consumption scenarios with significant economic and environmental impacts. Various efforts were made to reduce or replace the CRM content used in the obtaining process of high-performance materials. Complex concentrated alloys (CCAs) are an innovative solution due to their multitude of attractive characteristics, which make them suitable to be used in a wide range of industrial applications. In order to demonstrate their efficiency in use, materials should have improved recyclability, good mechanical or biocompatible properties, and/or oxidation resistance, according to their destination. In order to predict the formation of solid solutions in CCAs and provide the optimal compositions, thermodynamic and kinetic simulations were performed. The selected compositions were formed in an induction furnace and then structurally characterized with different techniques. The empirical results indicate that the obtained CCAs are suitable to be used in advanced applications, providing original contributions, both in terms of scientific and technological fields, which can open new perspectives for the selection, design, and development of new materials with reduced CRM contents. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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19 pages, 4651 KiB  
Article
Effect of Various Forms of Aluminum 6082 on the Mechanical Properties, Microstructure and Surface Modification of the Profile after Extrusion Process
by Piotr Noga, Andrzej Piotrowicz, Tomasz Skrzekut, Adam Zwoliński and Paweł Strzępek
Materials 2021, 14(17), 5066; https://doi.org/10.3390/ma14175066 - 4 Sep 2021
Cited by 9 | Viewed by 2248
Abstract
This article presents a method of reusing aluminum scrap from alloy 6082 using the hot extrusion process. Aluminum chips from milling and turning processes, having different sizes and morphologies, were cold pressed into briquettes prior to hot pressing at 400 °C at a [...] Read more.
This article presents a method of reusing aluminum scrap from alloy 6082 using the hot extrusion process. Aluminum chips from milling and turning processes, having different sizes and morphologies, were cold pressed into briquettes prior to hot pressing at 400 °C at a ram speed of 2 mm/s. The study of mechanical properties combined with observations of the microstructures, as well as tests of density, hardness and electrical conductivity were carried out. On the basis of the results, the possibility of using the plastic consolidation method and obtaining materials with similar to a solid ingot mechanical properties, density and electrical conductivity was proven. The possibility of modifying the surface of consolidated aluminum scrap was tested in processes examples: polishing, anodizing and coloring. For this purpose, a number of analyses and tests were carried out: comparison of colors on color histograms, roughness determination, SEM and chemical composition analysis. It has been proven there are differences in the surface treatment of the solid material and that of scrap consolidation, and as such, these differences may significantly affect the final quality. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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18 pages, 10780 KiB  
Article
Thermal Processing Map and Microstructure Evolution of Inconel 625 Alloy Sheet Based on Plane Strain Compression Deformation
by Yuelin Song, Jiangkun Fan, Xudong Liu, Peizhe Zhang and Jinshan Li
Materials 2021, 14(17), 5059; https://doi.org/10.3390/ma14175059 - 3 Sep 2021
Cited by 6 | Viewed by 2039
Abstract
Plane strain compression tests were used to study the deformation behavior of an Inconel 625 alloy sheet at various temperatures and strain rates. The peak stress was selected to establish the constitutive equation, and the processing maps under different strains were drawn. The [...] Read more.
Plane strain compression tests were used to study the deformation behavior of an Inconel 625 alloy sheet at various temperatures and strain rates. The peak stress was selected to establish the constitutive equation, and the processing maps under different strains were drawn. The results show that the effective stress–strain curve of Inconel 625 has typical dynamic recrystallization (DRX) characteristics. With the increasing deformation temperature and the decreasing strain rate, the softening effect is significantly enhanced. The parameters of the constitutive equation are calculated, and the average error of the constitutive equation is 5.68%. Through the analysis of the processing map, a deformation temperature of 950–960 °C with a strain rate of 0.007–0.05 s−1 were determined as the unstable region, and obvious local plastic-rheological zones were found in the unstable region. The optimum deformation condition was found to be 1020–1060 °C/0.005–0.03 s−1. Through electron backscattered diffraction (EBSD) characterization, it was found that both the increase of temperature and the decrease of strain rate significantly promote the recrystallization process. At a low strain rate, the main recrystallization mechanism is discontinuous dynamic recrystallization (DDRX). It is expected that the above results can provide references for the optimization of the rolling process and microstructure control of an Inconel 625 alloy sheet. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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15 pages, 3760 KiB  
Article
Unusual Force Constants Guided Distortion-Triggered Loss of Long-Range Order in Phase Change Materials
by Jiong Wang, Dongyu Cui, Yi Kong and Luming Shen
Materials 2021, 14(13), 3514; https://doi.org/10.3390/ma14133514 - 24 Jun 2021
Cited by 4 | Viewed by 1642
Abstract
Unusual force constants originating from the local charge distribution in crystalline GeTe and Sb2Te3 are observed by using the first-principles calculations. The calculated stretching force constants of the second nearest-neighbor Sb-Te and Ge-Te bonds are 0.372 and −0.085 eV/Å2 [...] Read more.
Unusual force constants originating from the local charge distribution in crystalline GeTe and Sb2Te3 are observed by using the first-principles calculations. The calculated stretching force constants of the second nearest-neighbor Sb-Te and Ge-Te bonds are 0.372 and −0.085 eV/Å2, respectively, which are much lower than 1.933 eV/Å2 of the first nearest-neighbor bonds although their lengths are only 0.17 Å and 0.33 Å longer as compared to the corresponding first nearest-neighbor bonds. Moreover, the bending force constants of the first and second nearest-neighbor Ge-Ge and Sb-Sb bonds exhibit large negative values. Our first-principles molecular dynamic simulations also reveal the possible amorphization of Sb2Te3 through local distortions of the bonds with weak and strong force constants, while the crystalline structure remains by the X-ray diffraction simulation. By identifying the low or negative force constants, these weak atomic interactions are found to be responsible for triggering the collapse of the long-range order. This finding can be utilized to guide the design of functional components and devices based on phase change materials with lower energy consumption. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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10 pages, 9125 KiB  
Article
Effect of High Strain Rate on Adiabatic Shearing of α+β Dual-Phase Ti Alloy
by Fang Hao, Yuxuan Du, Peixuan Li, Youchuan Mao, Deye Lin, Jun Wang, Xingyu Gao, Kaixuan Wang, Xianghong Liu, Haifeng Song, Yong Feng, Jinshan Li and William Yi Wang
Materials 2021, 14(8), 2044; https://doi.org/10.3390/ma14082044 - 19 Apr 2021
Cited by 3 | Viewed by 1946
Abstract
In the present work, the localized features of adiabatic shear bands (ASBs) of our recently designed damage tolerance α+β dual-phase Ti alloy are investigated by the integration of electron backscattering diffraction and experimental and theoretical Schmid factor analysis. At the strain rate of [...] Read more.
In the present work, the localized features of adiabatic shear bands (ASBs) of our recently designed damage tolerance α+β dual-phase Ti alloy are investigated by the integration of electron backscattering diffraction and experimental and theoretical Schmid factor analysis. At the strain rate of 1.8 × 104 s−1 induced by a split Hopkinson pressure bar, the shear stress reaches a maximum of 1951 MPa with the shear strain of 1.27. It is found that the α+β dual-phase colony structures mediate the extensive plastic deformations along α/β phase boundaries, contributing to the formations of ASBs, microvoids, and cracks, and resulting in stable and unstable softening behaviors. Moreover, the dynamic recrystallization yields the dispersion of a great amount of fine α grains along the shearing paths and in the ASBs, promoting the softening and shear localization. On the contrary, low-angle grain boundaries present good resistance to the formation of cracks and the thermal softening, while the non-basal slipping dramatically contributes to the strain hardening, supporting the promising approaches to fabricate the advanced damage tolerance dual-phase Ti alloy. Full article
(This article belongs to the Special Issue Light Alloys and High-Temperature Alloys)
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