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Nucleation mechanisms of dynamic recrystallization for G3 alloy during hot compression

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Rare Metals 2016年第7期35卷 543-550页

作者： Jue Wang Jian-Xin Dong Mai-cang zhang Jiangsu Key Laboratory of Advanced Structural Materials andApplication Technology Nanjing 211167China School of Materials Science and Engineering Nanjing Instituteof TechnologyNanjing 211167China School of Materials Science and Engineering University ofScience and Technology BeijingBeijing 100083China

Dynamic recrystallization （DRX） mechanisms of a nickel-based corrosion-resistant alloy, G3, were investigated by hot compression tests with temperatures from 1050 to 1200 ℃ and strain rates from 0.1 to 5.0 s-1. Deformation microstructure was observed at the strain from 0.05 to 0.75 by electron backscatter diffraction （EBSD） and transmission electron microscope （TEM）. Work hardening rate curves were calculated to analyze the effect of deformation parameters on the nucleation process. Results indicate that strain-induced grain boundary migration is the principal mechanism of DRX. Large annealing twins promote nucleation by accumulating dis- locations and fragmenting into cell blocks. Continuous dynamic recrystallization is also detected to be an effective supplement mechanism, especially at low temperature and high strain rate.

关键词： G3 alloy Dynamic recrystallization Nucleation mechanism Annealing twins

Effects of simulated on-fire processing conditions on the microstructure and mechanical performance of Q345R steel

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International Journal of Minerals,Metallurgy and Materials 2016年第1期23卷 49-56页

作者： Yi-chao Peng Hao-hao Xu Mai-cang zhang Department of Materials Technology Zhejiang Energy Technology & Research Co.Ltd. Department of Materials Science and Engineering University of Science and Technology Beijing

A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates＇ Brinell hardness, ten- sile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron micro- scope with the aim of investigating the effect of the steel＇s microstructure on its performance. All examined performance parameters exhib- ited a substantial decrease in the cases of samples heat-treated at temperatures near 700℃. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700℃, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical perform- ances were established to facilitate processing adjustments.

关键词： low alloy steels heat treatment mechanical properties microstructure nonlinear mathematical models

A new insight into rapid oxidation of alloy 925 contaminated by oxide powder

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Rare Metals 2021年第7期40卷 1872-1880页

作者： He Jiang Jian-Xin Dong Mai-cang zhang Jiang-Yang Li Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China

Rapid oxidation takes place both in the laboratory and in industrial conditions when alloy 925 is contaminated by oxide powder,and the oxidation rate is much higher than ***,the rapid oxidation behavior and mechanism of alloy 925 were investigated by a series of comparison tests at 1160℃.It is found that the oxide powder produced during the oxidation process is mainly composed of NiCr_(2)O_(4)spinel,accompanied by NiO and NiMoO_(4).The oxide powder plays a triggering role in the rapid oxidation of alloy 925,as NiO has a strong affinity with O.A composition adjustment experiment of alloy 925 shows that rapid oxidation is the synergetic effect of Mo and Cu in the *** and Cu easily combine to form low melting point *** formation and volatilization of MoO_(3)oxide can destroy the completeness of the protective oxide *** MoO_(3)flux can dissolve protective Cr_(2)O_(3)and prevent the repair of the oxide layer and also promote the formation of nonprotective and easy-spall NiCr_(2)O_(4)*** synergetic effect of Cu and Mo in accelerating oxidation should be considered in any nickel-based alloy with a high content of Cu and Mo.

关键词： Rapid oxidation Synergetic effect Nickelbased superalloy

Analytical Approximation to the(e)-Wave Solutions of the Hulthén Potential in Tridiagonal Representation

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Chinese Physics Letters 2011年第5期28卷 26-29页

作者： zhang Min-cang HUANG-FU Guo-Qing College of Physics and Information Technology Shaanxi Normal UniversityXi’an 710062 Department of Physics and Electronic Engineering Weinan Teachers UniversityWeinan 714000

The Schr(o)dinger equation with the Hulthén potential is studied by working in a complete square integrable basis that carries a tridiagonal matrix representation of the wave *** arbitrary e-wave solutions are obtained by using an approximation of the centrifugal *** resulting three-term recursion relation for the expansion coefficients of the wavefunction is presented and the wavefunctions are expressed in terms of the Jocobi *** discrete spectrum of the bound states is obtained by the diagonalization of the recursion relation.

关键词： diagonal Approximation integrable

Growth and Major Nutrient Concentrations in Brassica campestris Supplied with Different NH4^＋/NO3 Ratios

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Journal of Integrative Plant Biology 2007年第4期49卷 455-462页

作者： Fu-cang zhang Shao-Zhong Kang Fu-Sheng Li Jian-Hua zhang Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas of Ministry of Education Northwest A & F University Yangling 712100 China College of Water Resources and Civil Engineering China Agricultural University Beijing 100083 China College of Agriculture Guangxi University Nanning 530005 China Department of Biology Hong Kong Baptist University Hong Kong SAR China

In the present study, we investigated whether growth and main nutrient ion concentrations of cabbage （Brassica campestris L.） could be increased when plants were subjected to different NH4^＋/NO3- ratios. Cabbage seedlings were grown in a greenhouse in nutrient solutions with five NH4^＋/NO3- ratios （1：0; 0.75：0.25; 0.5：0.5; 0.25：0.75; and 0：1）. The results showed that cabbage growth was reduced by 87% when the proportion of NH4^＋-N in the nutrient solution was more than 75% compared with a ratio NH4^＋/NO3- of 0.5：0.5 35 d after transplanting, suggesting a possible toxicity due to the accumulation of a large amount of free ammonia in the leaves. When the NH4＋/NO3- ratio was 0.5：0.5, fresh seedling weight, root length, and H2PO4- （P）, K^＋, Ca^2＋, and Mg^2＋ concentrations were all higher than those in plants grown under other NH4^＋/NO3- ratios. The nitrate concentration in the leaves was the lowest in plants grown at 0.5： 0.5 NH4^＋/NO3-. The present results indicate that an appropriate NH4^＋/NO3- ratio improves the absorption of other nutrients and maintains a suitable proportion of N assimilation and storage that should benefit plant growth and the quality of cabbage as a vegetable.

关键词： cabbage (Brassica campestris), N nutrition NH4^+/NO3- ratio plant growth plant nutrition.

Particle Measurement Sensor for in situ determination of phase structure of fluidized bed

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Particuology 2009年第3期7卷 175-182页

作者： Qiang zhang cang Huang Dong Jiang Xiaobo Wei Zhen Qian Fei Wei Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical Engineering Tsinghua University Beijing 100084 China

Based on three-dimensional （3D） acceleration sensing, an intelligent particle spy capable of detecting, transferring, and storing data, is proposed under the name of Particle Measurement Sensor （PMS）. A prototype 60-mm-dia PMS was tested to track its freefall in terms of velocity and displacement, and served as a particle spy in a fluidized bed delivering the in situ acceleration information it detects. With increasing superficial gas velocity in the fluidized bed, the acceleration felt by PMS was observed to increase. The variance of the signals, which reflect the fluctuation, increased at first, reaching a maximum at the gas velocity （Uc） which marks the transition from bubbling to turbulent fluidization. Through probability density distribution （PDD） analysis, the PDD peak can be divided into the emulsion phase peak and the bubble phase peak. The average acceleration of emulsion and bubble phase increased, while the variance of both phases reached a maximum at Uc, at the same time. However, the difference between the variances of two phases reached the maximum at Uc. Findings of this study indicate that PMS can record independent in situ information. Further, it can provide other in situ measurements when equipped with additional multi-functional sensors.

关键词： Particle Measurement Sensor Fluidized bed Acceleration Gas-solid two-phase flow Phase structure

Relationship Between Grain Boundary Segregation of Antimony and Temper Embrittlement in Titanium-Doped Nickel-Chromium Steel

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Journal of Iron and Steel Research International 2011年第1期18卷 68-72页

作者： ZHENG Lei zhang Mai cang DONG Jian-xin MENG Ye School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083China

The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibium and the kinetics of temper embrittlement agrees well with those of nonequilibrium antimony segregation at grain boundary. Besides, the mechanism of nonequilibrium antimony segregation at grain boundary proved to be the most satisfactory one among the existing mechanisms to interpret the antimony induced embrittlement kinetics in the nick- el-chromiunl steel. Based on these, the activation energy and frequency factor of diffusion of antimony vacancy complexes were obtained according to the concept of critical time in nonequilibrium grain boundary segregation theory.

关键词： grain boundary segregation temper embrittlement critical time diffusion activation energy

Hot corrosion behavior and mechanism of FGH96 P/M superalloy in molten NaCl–Na_2SO_4 salts

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Rare Metals 2019年第2期38卷 173-180页

作者： He Jiang Jian-Xin Dong Mai-cang zhang Lei Zheng Zhi-Hao Yao Materials Science and Engineering University of Science and Technology Beijing

Hot corrosion behavior of FGH96 powder metallurgy(P/M) superalloy in 25 % NaCl + 75 % Na_2SO_4 molten salts at 650, 700, and 750 ℃ was investigated in this paper. The methods of mass loss measurement, X-ray diffraction(XRD), scanning electron microscopy(SEM),and energy-dispersive spectroscopy(EDS) were used *** experimental results show that hot corrosion kinetics follows a square power law at 650 ℃, while a linear one at 700 and 750 ℃. The corrosion layer is detected to be composed of Cr_2O_3, NiO, and Ni2S_3 at each *** cross-sectional morphologies and corresponding elemental maps indicate that the corrosion layer is a stratified structure of oxide and sulfide. The results and analyses confirm that the hot corrosion mechanism of FGH96 P/M superalloy is a cooperate process of oxidation and sulfidation. Furthermore, the relatively higher concentrations of Cr, Co, and Ti provide better corrosion resistance to the attack of S and Cl^-.

关键词： Nickel-based superalloy FGH96 Hot corrosion Molten salts

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