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17 pages, 5441 KiB

Open AccessArticle

First Principles Investigation of the Effects of Chemical Short-Range Ordering Clusters on the Ideal Tensile Strength and Ductility of Aluminum Alloys

by Xiangkai Chen, Xiaohua Chen, Zidong Wang, Yanlin Wang, Kaixuan Chen and Yuzhi Zhu

Metals 2022, 12(12), 2143; https://doi.org/10.3390/met12122143 - 14 Dec 2022

Cited by 1 | Viewed by 1383

Abstract

As important structural features of the metal materials, chemical short-range ordering clusters play a critical role in the mechanical properties of the materials. They have been discovered in dilute Al-alloy systems and are usually generated by annealing processes at high temperatures or by [...] Read more.

As important structural features of the metal materials, chemical short-range ordering clusters play a critical role in the mechanical properties of the materials. They have been discovered in dilute Al-alloy systems and are usually generated by annealing processes at high temperatures or by severe plastic deformation at room temperature. In the present work, systematic first-principle calculations were conducted to evaluate the influences of the chemical short-range ordering clusters L1₂-Al₃Zr on the mechanical properties of the pure Al supercell. Results showed that the mechanical properties including both ideal tensile strength and ductility were improved simultaneously when the chemical short-range ordering clusters L1₂-Al₃Zr were introduced to the pure Al. The larger the volume fraction of chemical short-range ordering clusters L1₂-Al₃Zr, the larger the ideal tensile strength. The deformation charge density, the electron localization function and the density of state were computed to reveal the nature of the strengthening of the chemical short-range ordering clusters L1₂-Al₃Zr on the pure Al supercell. It was found that excellent ideal tensile strength for the Al supercell with the chemical short-range ordering clusters L1₂-Al₃Zr was due to strong charge accumulations and strong electronic interactions between the solute atoms Zr and the host Al atoms. In addition, the Pugh ratio (B/G) and ratio (W_sep/G_disl) of the work of the separation W_sep to the work of dislocation emission G_disl were computed to reveal the effect of the chemical short-range ordering clusters L1₂-Al₃Zr on the ductility of the Al supercell. Results showed that the addition of L1₂-Al₃Zr chemical short-range ordering clusters addition to pure Al supercell brought about an increase in ductility as compared to pure Al supercell, which is ascribed to large the Pugh ratio B/G and ratio (W_sep/G_disl) of the work of the separation W_sep to the work of dislocation emission G_disl. This work is important for simultaneously improving the tensile strength and ductility of Al alloys. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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15 pages, 5113 KiB

Open AccessArticle

Effects of Pressure on Homogeneous Nucleation and Growth during Isothermal Solidification in Pure Al: A Molecular Dynamics Simulation Study

by Xiaohua Chen, Weijie Fan, Wenwen Jiang, Deye Lin, Zidong Wang and Simeng Jiang

Metals 2022, 12(12), 2101; https://doi.org/10.3390/met12122101 - 7 Dec 2022

Cited by 1 | Viewed by 1426

Abstract

Effects of different pressures on the isothermal-solidification process of pure Al were studied by molecular dynamics (MD) simulation using the embedded-atom method (EAM). Al was first subjected to a rapid-cooling process, and then it was annealed under different pressures conditions. Mean first-passage times [...] Read more.

Effects of different pressures on the isothermal-solidification process of pure Al were studied by molecular dynamics (MD) simulation using the embedded-atom method (EAM). Al was first subjected to a rapid-cooling process, and then it was annealed under different pressures conditions. Mean first-passage times (MFPT) method, Johnson-Mehl-Avrami (JMA) law, and X-ray diffraction (XRD) simulation analysis method were used to qualify the solidification- kinetic processing. Nucleation rate, critical-nucleus size, Avrami exponent, growth exponent, and crystallite size were calculated. Results show that the nucleation rate increases as the pressure increases. The change of critical-nucleation size is not obvious as the pressure increases. With the pressure increasing, growth exponent decreases, indicative of decreased grain-growth rate. It was also found that with the pressure increasing, the Avrami exponent decreases, indicating that the increased pressure has an effect on growth modes during solidification, which changes from three-dimensional growth to one-dimensional growth. Results of XRD simulation shows that with pressure increasing, crystallite size decreases. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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10 pages, 3674 KiB

Open AccessArticle

Research on Optimization Design of Cast Process for TiAl Case Casting

by Xiaoping Zhu, Chunlei Zhu, Baosen Lin and Zidong Wang

Metals 2022, 12(11), 1954; https://doi.org/10.3390/met12111954 - 15 Nov 2022

Cited by 2 | Viewed by 1271

Abstract

The effect of the cast process procedure and pouring systems on several typical metallurgical defects for TiAl case casting was studied by numerical simulation and pouring test. The results indicated that gravity casting had much better melt-filling stability and synchronization, compared to centrifugal [...] Read more.

The effect of the cast process procedure and pouring systems on several typical metallurgical defects for TiAl case casting was studied by numerical simulation and pouring test. The results indicated that gravity casting had much better melt-filling stability and synchronization, compared to centrifugal casting. Misrun defects in the upper edge of the thin-walled outer ring could be removed by increasing the bottom cross runners, and the negative effect of the overheated zone in the thick-walled flange could be reduced by designing a suitable inner-gate structure. The crack induced by stress concentration in the transition zone brought significant challenges for TiAl case casting and the issue would be effectively resolved through structural design and process optimization. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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16 pages, 11988 KiB

Open AccessArticle

Microstructural Evolution of Wrought-Nickel-Based Superalloy GH4169

by Wei Zhou, Xiaohua Chen, Yanlin Wang, Kaixuan Chen, Yuzhi Zhu, Junwei Qin, Zidong Wang and Lingli Zuo

Metals 2022, 12(11), 1936; https://doi.org/10.3390/met12111936 - 11 Nov 2022

Cited by 1 | Viewed by 1617

Abstract

To investigate the microstructural evolution of wrought-nickel-based superalloy GH4169 from the original ingot to the finished product of manufacturing processes, different kinds of etchants and etching methods were used to show the fine precipitates and their morphologies. The obtained microstructures can vary in [...] Read more.

To investigate the microstructural evolution of wrought-nickel-based superalloy GH4169 from the original ingot to the finished product of manufacturing processes, different kinds of etchants and etching methods were used to show the fine precipitates and their morphologies. The obtained microstructures can vary in size, type, distribution, location, formation, and interactions of multiple phases, which were observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and an energy dispersive spectrometer (EDS). The dendrite segregation behavior of as-cast superalloy GH4169 was investigated. In addition, the microstructural evolution mechanism of second-phase particles during dynamic recrystallization was analyzed. This work sheds light on the evolution of the second-phase structure of nickel-based superalloys during the preparation process, providing guidance for process development and visual interpretation of the relationships between microstructure and properties. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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13 pages, 5217 KiB

Open AccessArticle

Morphology of Inclusions and Its Refinement Mechanism in the New P91 Heat-Resistant Pipeline Steel

by Xiaohua Chen, Shenghui Liang, Yanlin Wang, Zidong Wang, Weijie Fan, Xinning Yu and Jian Yang

Metals 2022, 12(10), 1556; https://doi.org/10.3390/met12101556 - 20 Sep 2022

Cited by 2 | Viewed by 1086

Abstract

A new type of P91 heat-resistant pipeline steel ingot was prepared by feeding Al twisted wire into a steel melt through a multi-point regional micro-supply method, combined with electromagnetic stirring. The type, shape, and size of inclusions in the new P91 steel after [...] Read more.

A new type of P91 heat-resistant pipeline steel ingot was prepared by feeding Al twisted wire into a steel melt through a multi-point regional micro-supply method, combined with electromagnetic stirring. The type, shape, and size of inclusions in the new P91 steel after forging were then analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscope (TEM). The results showed that four types of inclusions were detected in the P91 steel, including: spherical independent Al₂O₃ inclusions, irregular Al₂O₃-SiO₂ composite inclusions, nearly spherical MgO-Al₂O₃ composite inclusions, and spherical (Ca, Mg, Al) (O) composite inclusions. Compared with traditional P91 steel, the inclusions in the new P91 steel were significantly refined. Refining mechanisms of inclusion showed that Al₂O₃ oxide particles distributed dispersedly with fine sizes could be obtained through a multi-point regional micro-supply method. Further, Al₂O₃ particles act as the nucleation core to form a “core-shell” structure and play the role of a heterogeneous nucleation to refine SiO₂, MgO, (Ca, Mg) (O), and other inclusions in the steel. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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10 pages, 3738 KiB

Open AccessArticle

Mechanism of Balanced Strength and Ductility in High-Strength Low-Alloy Steel

by Yuzhi Zhu, Yunke Jia, Xiaohua Chen, Yanlin Wang and Zidong Wang

Metals 2022, 12(10), 1554; https://doi.org/10.3390/met12101554 - 20 Sep 2022

Cited by 1 | Viewed by 1357

Abstract

A high-strength low-alloy steel with balanced strength and ductility was reported. A product of the strength and elongation (PSE) at a break of ~19 GPa% was obtained. The microstructure of the material was investigated by scanning electron microscopy, electron backscattered diffraction, and transmission [...] Read more.

A high-strength low-alloy steel with balanced strength and ductility was reported. A product of the strength and elongation (PSE) at a break of ~19 GPa% was obtained. The microstructure of the material was investigated by scanning electron microscopy, electron backscattered diffraction, and transmission electron microscopy methods. Phase transformation follows the K–S orientation relationships. Interconnecting structures generate due to the variant interactions within one prior austenite grain. The multi-phase microstructure containing both soft and hard phases contributes to good plasticity. The homogeneously distributed NbC nanoparticles make up the loss of strength ascribed to the soft retained austenite and keep the strength at an extremely high level. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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16 pages, 2212 KiB

Open AccessArticle

The Effect of the Shear Flow on Columnar Crystal Growth in an Undercooled Melt

by Mingwen Chen, Jiaxuan Jiang, Linyi Li and Zidong Wang

Metals 2022, 12(9), 1487; https://doi.org/10.3390/met12091487 - 8 Sep 2022

Cited by 1 | Viewed by 1241

Abstract

Herein, the effect of the shear flow on the growth of columnar crystals in an undercooled melt is studied. The asymptotic method is used to solve the dynamic model for the growth of a columnar crystal. The resulting asymptotic solution shows that the [...] Read more.

Herein, the effect of the shear flow on the growth of columnar crystals in an undercooled melt is studied. The asymptotic method is used to solve the dynamic model for the growth of a columnar crystal. The resulting asymptotic solution shows that the shear flow significantly changes the interface morphology of the columnar crystal. With the shear effect of the forced flow, the growth rate of the columnar interface increases in the shear direction of the shear flow. As the shear rate of the shear flow further increases, the interface of the columnar crystal is seriously deformed and distorted. The shear flow causes the columnar crystal in the undercooled melt to tend to evolve into smaller crystals in the initial stage of crystal growth. The analytical result provides a prediction of the formation of interface microstructures during solidification through the change of processing parameters. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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13 pages, 1433 KiB

Open AccessArticle

The Effect of the Shear Flow on the Morphological Pattern of Particles in an Undercooled Melt

by Mingwen Chen, Jinhui Zhao, Yan Chen, Guanjie Zheng and Zidong Wang

Metals 2022, 12(9), 1469; https://doi.org/10.3390/met12091469 - 2 Sep 2022

Viewed by 1119

Abstract

The effect of shear flow on the morphological pattern of particles in an undercooled melt is studied by using the asymptotic method. The mathematical model of the particle includes the anisotropic interface kinetic undercooling. The asymptotic solution for the mathematical model of the [...] Read more.

The effect of shear flow on the morphological pattern of particles in an undercooled melt is studied by using the asymptotic method. The mathematical model of the particle includes the anisotropic interface kinetic undercooling. The asymptotic solution for the mathematical model of the particle shows that shear flow in an undercooled melt intensifies the deformation and distortion of the particle in the initial stage of crystal growth. Due to the shear flow, the growth rate of the interface increases in the shear direction of the flow and strengthens the inward decay of the part of the interface induced by the anisotropic interface kinetics in the initial stage of crystal growth. As the shear rate of the flow increases, the interface of the particle is seriously deformed and distorted until it breaks into smaller particles. The analytical result provides the prediction of the formation of interface microstructures during solidification through the change of processing parameters. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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Review

Jump to: Research

32 pages, 8132 KiB

Open AccessReview

In-Situ Fabrication, Microstructure and Mechanical Performance of Nano Iron-Rich Precipitate Reinforced Cu and Cu Alloys

by Zongxuan Li, Kaixuan Chen, Xiaohua Chen, Yuzhi Zhu, Mingwen Chen, Yanlin Wang, Jiangxu Shen, Jiayun Shi and Zidong Wang

Metals 2022, 12(9), 1453; https://doi.org/10.3390/met12091453 - 30 Aug 2022

Cited by 4 | Viewed by 1395

Abstract

In this paper, the research progress on the strengthening of copper and copper alloy is reviewed. The research shows that traditional strengthening methods are often accompanied by the decrease of plasticity, and there are limitations in size, cost, and other aspects in the [...] Read more.

In this paper, the research progress on the strengthening of copper and copper alloy is reviewed. The research shows that traditional strengthening methods are often accompanied by the decrease of plasticity, and there are limitations in size, cost, and other aspects in the process. The in-situ nanoparticle strengthening and plasticizing technology proposed in recent years can avoid the above problems. In this paper, the idea of in-situ nanoparticle strengthening is introduced to realize the simultaneous enhancement of strength and ductility of as-cast pure copper and tin bronze alloys. The effects of in-situ precipitation of iron-rich nanoparticles on the microstructure, and mechanical properties of different copper alloy systems, are systematically elucidated based on the former characterization and mechanical testing results. The results show that the in-situ introduction of iron-rich nanoparticles in the copper systems induces the formation of a nano precipitate-fine grain (NPFG) structure, which greatly improves the strength and ductility of copper alloys. The evolution of size, distribution, number density, morphology evolution in iron-rich nanoparticles, and the formation mechanism of NPFG structure, as well as the mechanism of NPFG strengthening and toughening, are summarized. An industrial-applicable casting process is proposed to prepare bulk NPFG structured copper alloys with complex shape, high strength, and high ductility. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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21 pages, 8940 KiB

Open AccessReview

Fabrication Techniques and the Formation Mechanism of Nanoparticles and Nanoclusters in Metal Materials

by Junwei Qin, Xiaohua Chen, Yanlin Wang, Yuzhi Zhu, Shiwei Pan, Wei Zhou, Mingwen Chen and Zidong Wang

Metals 2022, 12(9), 1420; https://doi.org/10.3390/met12091420 - 28 Aug 2022

Cited by 2 | Viewed by 1767

Abstract

Continuous innovation in the design of metallic materials is essential for further progress in aerospace, automotive, construction, and shipping. Fine grain strengthening is considered to increase the strength of metals without losing plasticity. However, many fabrication techniques are restricted to very small sizes. [...] Read more.

Continuous innovation in the design of metallic materials is essential for further progress in aerospace, automotive, construction, and shipping. Fine grain strengthening is considered to increase the strength of metals without losing plasticity. However, many fabrication techniques are restricted to very small sizes. Recently, the introduction of in situ nanoparticles with coherent or semi-coherent interfaces in the metallic matrix achieves simultaneous enhancement of the strength and ductility of metallic materials. In this review, the focus is on fabrication techniques and the formation mechanism of nanoparticles and nanoclusters in metal materials. The effects of nanoparticles on grain refinement, inhibiting segregation, second phase, and inclusion refinement are discussed, and the mechanism of simultaneous improvement in the strength and ductility of nanostructured metal materials is briefly covered. Finally, we provide a summary and outline of the possible direction for further advances in this research field. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Nanocrystalline Metals)

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