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mechanism of α-Cr precipitation and crystallographic relationships between α-Cr and δ phases in Inconel 718 alloy after long-time thermal exposure

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International Journal of Minerals,Metallurgy and Materials 2010年第3期17卷 312-317页

作者： Zhong-nan Bi Jian-xin Dong Mai-cang Zhang Lei Zheng Xi-shan Xie School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

To study the precipitation mechanism of α-Cr phase in Inconel 718 alloy, the samples after long-time aging at 650 and 677℃ were examined by microstructural observations and chemical phase analysis methods. Combining the thermodynamics and kinetics calculation results, α-Cr always precipitates in the vicinity of δ phase, because δ phase rejects Cr into the γ-matrix when growing. The selected area diffraction patterns confirm that the crystallographic relationships of α-Cr with 6 phase are （010）d/（1- 10）*** and [100]d/If 11 ]α-Cr- A graphic model is also presented to show the crystallographic relation between α-Cr and δ phases.

关键词： Inconel 718 precipitation mechanism crystallography thermodynamics kinetics

XRD Synchrotron Study of Carbide precipitation in Martensitic Steels During Tempering

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Acta Metallurgica Sinica(English Letters) 2013年第5期26卷 553-557页

作者： C.Bellot P.Lamesle D.Delagnes Universit de Toulouse Mines Albi INSAISAE ICA(Institut Clment Ader) Campus Jarlard Aubert&Duval

In order to improve the knowledge of the precipitation mechanism in martensitic steels containing carbon,XRD synchrotron experiments were performed. Firstly, the influence of Ni,Co and Al were studied and it was found that the precipitation of iron carbides occurs in same way as in Fe-C steel. However, with the addition of molybdenum and chromium in same steels, XRD synchrotron investigations clearly showed alloyed carbides directly precipitate, thereby preventing the iron carbides formation.

关键词： Carbon Martensite Iron carbide Cementite precipitation mechanism

Effect of superplastic deformation on precipitation behavior of sigma phase in 3207 duplex stainless steel

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Progress in Natural Science:Materials International 2021年第2期31卷 334-340页

作者： Jingkun Li Xueping Ren Yanling Zhang Hongliang Hou Xiaodan Gao School of Materials Science and Engineering University of Science and Technology Beijing AVIC Manufacturing Technology Institute Institute for Advanced Materials and Technology University of Science and Technology Beijing

Owing to excellent strength, toughness and corrosion resistance, duplex stainless steels(DSS) are widely used in constructional and petrochemical applications. Sigma phase, which has detrimental impact on the properties, is readily precipitated during hot working of DSS. However, precipitation behavior of sigma phase during superplastic deformation, which is the most significant processing method of DSS, is still unclear. In the current study,the effect of superplastic deformation on the precipitation behavior of sigma phase was investigated in 3207 duplex stainless steel. The result shows that superplastic deformation could prevent sigma phase precipitation generally by increasing mobility of grain boundaries and decreasing misorientation of the sigma phase boundaries, resulting in some sigma phase precipitated on the twin boundaries. Most of the sigma phase precipitated on ferrite-austenite interface with misorientation of 20–25°, while it precipitated in ferrite or austenite with the misorientation of 40°–45°. The orientation relationship between sigma phase and matrix matched well in austenite and on the ferrite/austenite interfaces, while it showed a small misfit in ferrite. The prevention effect of the superplastic deformation on the sigma phase precipitation was beneficial to quasi stable deformation stage,resulting in longer elongation.

关键词： Duplex stainless steel Superplastic deformation Sigma phase (σ) precipitation mechanism Hardening effect

Size controllable synthesis and photocatalytic performance of mesoporous TiO2 hollow spheres

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Journal of Materials Science & Technology 2020年第13期47卷 105-113页

作者： Nattakan Kanjana Wasan Maiaugree Phitsanu Poolcharuansin Paveena Laokul Department of Physics Faculty of ScienceMahasarakham UniversityKham Riang Sub-DistrictKhantarawichai DistrictMaha Sarakham44150Thailand

Hollow mesoporous TiO2 spheres(THs)were prepared via template-directed deposition of TiO2 nanoparticles on the surface of carbon *** carbon spheres were used as hard *** diameters were controlled by pH adjustment prior to a hydrothermal *** properties,such as crystallinity,optical characteristics,microstructure and surface morphology of the samples were *** results showed that the diameter of the carbon template could be well controlled in the range of 397-729 nm by adjusting the initial pH value of the dextrose solution from 3 to *** TiO2 spheres with average diameters ranging from 171 to 668 nm and shell thicknesses ranging from 28 to 47 nm formed by heat treatment at 450℃.The photocatalytic performance of hollow TiO2 spheres and TiO2 nanoparticles was examined under UVA irradiation using a methyl orange aqueous solution as an artificial *** study revealed that the THs synthesized using a dextrose solution at pH 7 had a higher photocatalytic activity compared to other samples since it had the lowest shell thickness and the proper optical band gap of 3.12 eV with the longest lifetime of electron-hole pair separation.

关键词： TiO2 Photocatalytic activity Mesoporous titania Hydrothermal method precipitation mechanism

Computer simulation for the precipitation process of Ni75Al7.5V17.5 alloy

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Progress in Natural Science:Materials International 2004年第12期 67-71+108页

作者： LI Yongsheng*, CHEN Zheng, LU Yanli, WANG Yongxin and ZHANG Jianjun(Department of Material Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China)

The precipitation mechanism of Ni 75 Al 7.5 V 17.5 alloy above the L1 2 instability line, between the L1 2 and D0 22 instability lines and below the D0 22 instability line are studied using microscopic phase field kinetic equation. This paper is aimed at investigating the effect of temperature on precipitation mechanism and morphological evolution of the alloy. Our simulations demonstrate that the precipitation is a mixed mechanism of non classical nucleation growth and spinodal decomposition above the L1 2 instability line. It needs certain thermal fluctuations for nucleation and the number of θ phases is small at this temperature. The precipitation mechanism of γ′ phase is congruent ordering followed by spinodal decomposition, and θ phase is a mixed mechanism of non classical nucleation growth and spinodal decomposition between the L1 2 and D0 22 instability lines. The mechanism below the D0 22 instability line is similar to that between the L1 2 and D0 22 instability lines. With the decrease of the temperature, ordering and phase separation becomes fast, the dimension of γ′ phase becomes small, the shape transforms from equiaxed to block, the dimension of θ phase becomes large and the shape transforms from strip to circle.

关键词： precipitation mechanism atomic configuration order parameter Ni75Al7.5V17.5 alloys computer simulation.

Rare earth element and yttrium compositions of the Paleoproterozoic Yuanjiacun BIF in the Lliang area and their implications for the Great Oxidation Event(GOE)

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Rare earth element and yttrium compositions of the Paleoprot...