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Structural refinement of 00Cr13Ni5Mo2 supermartensitic stainless steel during single-stage intercritical tempering

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International Journal of Minerals,Metallurgy and materials 2014年第3期21卷 279-288页

作者： Da-kun Xu Yong-chang Liu zong-qing ma Hui-jun Li Ze-sheng Yan State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Material Science and Engineering Tianjin University

The 00Cr13Ni5Mo2 supermartensitic stainless steel was first tempered at 570-730°C for 2 h to observe the microstructure and hardness changes. The tempering temperature was set to 600, 650, and 700°C, which is below, equal to, and above the austenite transformation start temperature, respectively, for each holding period to investigate the effects of tempering time on the structure and properties of the steel. The microstructure of the specimens was examined by optical microscopy and transmission electronic microscopy, and the phase composition was detected by X-ray diffraction. As expected, lath refinement was observed in the steel tempered at 700°C, and the refinement degree significantly depended on the tempering time. Contrary to normal steel softening by tempering, the hardness performance of the steel was significantly enhanced primarily because of the refinement of martensite laths after single-stage intercritical tempering. It is believed that the reverse transformation of martensite（α′） to austenite（γ） is responsible for the refinement.

关键词： stainless steel tempering retained austenite phase transitions

Evaluation of precipitation hardening in TiC-reinforced Ti_2AlNb-based alloys

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International Journal of Minerals,Metallurgy and materials 2018年第4期25卷 453-458页

作者： Ya-ran Zhang Qi Cai Yong-chang Liu zong-qing ma Chong Li Hui-jun Li State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Materials Science and Engineering Tianjin University materials Genome Institute Shanghai University

Ti2AlNb-based alloys with 0.0 wt%, 0.6 wt%, and 2.0 wt% carbon nanotube（CNT） addition were fabricated from spherical Ti–22 Al–25 Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050℃ were identified as TiC and facilitated the transformation of α2 ＋ B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2 ＋O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0 wt% CNT addition increased to HV 429 ± 9.

关键词： Ti2AlNb alloy carbides microstructure precipitation hardening hardness

Effects of aluminum and titanium on the microstructure of ODS steels fabricated by hot pressing

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International Journal of Minerals,Metallurgy and materials 2018年第10期25卷 1156-1165页

作者： Qian Zhao Li-ming Yu Yong-chang Liu Yuan Huang zong-qing ma Hui-jun Li State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science & Engineering Tianjin University

Three oxide-dispersion-strengthened(ODS)steels with compositions of Fe-14Cr-2W-0.2V-0.07Ta-0.3Y_2O_3(wt%,so as the follows)(14Y),Fe-14Cr-2W-0.2V-0.07Ta-1Al-0.3Y_2O_3(14YAl),and Fe-14Cr-2W-0.2V-0.07Ta-0.3Ti-0.3 Y_2O_3(14YTi)were fabricated by hot pressing.Transmission electron microscopy(TEM)was used to characterize the microstructures and nanoparticles of these ODS steels.According to the TEM results,14Y,14YAl,and 14YTi ODS steels present similar bimodal structures containing both large and small grains.The addition of Al or Ti has no obvious effect on the microstructure of the steels.The spatial and size distribution of the nanoparticles was also analyzed.The results indicate that the average size of nanoparticles in the 14YTi ODS steel is smaller than that in the 14YAl ODS steel.Nanoparticles such as Y_2O_3,Y_3Al_5O_(12) and YAlO_3,and Y_2Ti_2O_7 were identified in the 14Y,14YAl,and 14YTiODS steels,respectively.

关键词： hot pressing ODS steel mechanical alloying bimodal structure nanoparticle aluminum titanium

Morphology and quantitative analysis of O phase during heat treatment of hot-deformed Ti_2AlNb-based alloy

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International Journal of Minerals,Metallurgy and materials 2018年第10期25卷 1191-1200页

作者： Hong-yu Zhang Chong Li zong-qing ma Li-ming Yu Hui-jun Li Yong-chang Liu State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science & Engineering Tianjin University

A 1040°C-hot-deformed Ti_2AlNb-based alloy solution-treated at 950°C and aged at different temperatures was quantitatively investigated. The microstructure, size of the phase, and microhardness of the deformed alloys were measured. The results indicated that the microstructure of the deformed Ti_2AlNb-based alloy specimens comprise coarse O lath, fine O lath, equiaxed O/α_2, and acicular O phase. More O phase was generated in the deformed alloy after heat treatment because the acicular O phase was more likely to nucleate and grow along the deformation-induced crystal defects such as dislocations and subgrain boundaries. After deformation and subsequent heat treatment, the acicular O phase of the resultant alloy became finer compared to that of the undeformed alloy, and the acicular O phase became coarser and longer with the elevated aging temperature, while the width of the O lath exhibited unobvious variations. The hot deformation facilitated the dissolution of the O lath but accelerated the precipitation of the acicular O phase. When the 950°C-solution-treated deformed Ti_2AlNb-based alloy was then aged at 750°C for different periods, the phase content was nearly invariable, O and B2 phases eventually reached equilibrium, and the microstructure became stable and homogeneous.

关键词： Ti2AlNb-based alloys hot deformation solution treatment aging microstructure

Hot deformation behaviors of a 9Cr oxide dispersion-strengthened steel and its microstructure characterization

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International Journal of Minerals,Metallurgy and materials 2019年第5期26卷 597-610页

作者： Yu Shao Li-ming Yu Yong-chang Liu zong-qing ma Hui-jun Li Jie-feng Wu State Key Lab of Hydraulic Engineering Simulation and Safety Tianjin Key Lab of Composite and Functional Materials Tianjin University Institute of Plasma Physics Chinese Academy of Sciences

The hot deformation behaviors of a 9 Cr oxide dispersion-strengthened(9 Cr-ODS) steel fabricated by mechanical alloying and hot isostatic pressing(HIP) were investigated. Hot compression deformation experiments were conducted on a Gleeble 3500 simulator in a temperature range of 950–1100°C and strain rate range of 0.001–1 s^(-1). The constitutive equation that can accurately describe the relationship between the rheological stress and the strain rate of the 9 Cr-ODS steel was established, and the deformation activation energy was calculated as 780.817 kJ/mol according to the data obtained. The processing maps of 9 Cr-ODS in the strain range of 0.1–0.6 were also developed. The results show that the region with high power dissipation efficiency corresponds to a completely recrystallized structure. The optimal processing conditions were determined as a temperature range of 1000–1050°C with strain rate between 0.003 and 0.01 s^(-1).

关键词： hot deformation constitutive equations processing maps microstructural evolution

Effect of microstructure variation on the corrosion behavior of high-strength low-alloy steel in 3.5wt% NaCl solution

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International Journal of Minerals,Metallurgy and materials 2015年第6期22卷 604-612页

作者： Yu-bing Guo Chong Li Yong-chang Liu Li-ming Yu zong-qing ma Chen-xi Liu Hui-jun Li State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Materials Science and EngineeringTianjin University

The effect of microstructure variation on the corrosion behavior of high-strength low-alloy（HSLA） steel was investigated. The protective property of the corrosion product layer was also explored. Experimental results reveal that the type of microstructure has significant effect on the corrosion resistance of HSLA steel. The measurement results of weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy indicate that the steel with acicular ferrite microstructure exhibits the lowest corrosion rate. martensite exhibits a reduced corrosion resistance compared with polygonal ferrite. It is found that the surface of the acicular ferrite specimen uniformly covered by corrosion products is seemingly denser and more compact than those of the other two microstructures, and can provide some amount of protection to the steel; thus, the charge transfer resistance and modulus values of the acicular ferrite specimen are the largest. However, corrosion products on martensite and polygonal ferrite are generally loose, porous, and defective, and can provide minor protectiveness; thus, the charge transfer resistance values for polygonal ferrite and martensite are lower.

关键词： high-strength low-alloy steel microstructure corrosion sodium chloride solutions

Effect of deformation twinning on high-temperature performance of cold-rolled S31042 steel

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Journal of Iron and Steel Research(International) 2019年第7期26卷 704-711页

作者： Yan-mo Li Yong-chang Liu Li-ming Yu Chen-xi Liu Chong Li Yuan Huang Hui-jun Li zong-qing ma State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science and Engineering Tianjin University Tianjin 300354 China

Influence of deformation twinning on high-temperature instantaneous performance of cold-rolled S31042 steel was investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, and high-temperature tensile test. An increasing number of deformation twins have formed as the cold rolling reduction degree increases during the cold rolling process. During the tensile process at 700 ℃, M23C6 particles generated along the deformation twin boundaries, and NbCrN nanoparticles dispersedly precipitated throughout the austenite grains. For the high-temperature tensile sample subjected to cold reduction for 80%, it is observed from the fractured cross section that numerous defor-mation twin boundaries were decorated by discontinuous M23C6 particles. Therefore, austenite grains were divided into several independent zones by the deformation twins, and the grains were refined. Due to the grain refinement strengthening and precipitation strengthening, the high-temperature temporal strength of the 80% cold-rolled sample was significantly improved, and simultaneously, this sample exhibited favorable high-temperature elongation.

关键词： S31042 steel Cold rolling Deformation twinning Carbide precipitation High-temperature performance

Deterministic and Robust Volt-var Control Methods of Power System Based on Convex Deep Learning

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 719-729页

作者： qing ma Changhong Deng IEEE the School of Electrical Engineering and Automation Wuhan University

Volt-var control(VVC) is essentially a non-convex optimization problem due to the non-convexity of power flow(PF) constraints, resulting in the difficulty in obtaining the optimum without convexity conversion. The existing second-order cone method for the convexity conversion often leads to a sharp increase in PF constraints and optimization variables, which in turn increases the optimization difficulty or even leads to optimization failure. This paper first proposes a deterministic VVC method based on convex deep learning power flow(DLPF). This method uses the input convex neural network(ICNN) to establish a single convex mapping between state parameters and node voltage to complete the convexity conversion while the optimization variables only correspond to reactive power equipment, which can ensure the global optimum with extremely fast computation speed. To cope with the impact brought by the uncertainty of distributed energy and omit the additional worst scenario search of traditional robust VVC, this paper proposes robust VVC method based on convex deep learning interval power flow(DLIPF), which continues to adopt ICNN to establish another convex mapping between state parameters and node voltage interval. Combining DLIPF with DLPF, this method decreases the modeling and optimization difficulty of robust VVC significantly. Test results on 30-bus, 118-bus, and 200-bus systems prove the correctness and rapidity of the proposed methods.

关键词： Optimization Reactive power mathematical models Deep learning Uncertainty Load flow Programming

Data driven analysis reveals prognostic genes and immunological targets in human sepsis-associated acute kidney injury

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World Journal of Emergency Medicine 2024年第2期15卷 91-97页

作者： qing Zhao Jinfu ma Jianguo Xiao Zhe Feng Hui Liu Department of Diagnosis and Treatment of Cadres the First Medical CenterChinese PLA General HospitalBeijing 100853China Intensive Care Unit the 305th Hospital of Chinese PLABeijing 100032China Department of Critical Care Medicine the First Medical CenterChinese PLA General HospitalBeijing 100853China Nephrology Department the First Medical CenterChinese PLA General HospitalBeijing 100853China

BACKGROUND:The molecular mechanism of sepsis-associated acute kidney injury(SA-AKI)is unclear.We analyzed co-differentially expressed genes(co-DEGs)to elucidate the underlying mechanism and intervention targets of SA-AKI.METHODS:The microarray datasets GSE65682,GSE30718,and GSE174220 were downloaded from the Gene Expression Omnibus(GEO)database.We identified the co-DEGs and constructed a gene co-expression network to screen the hub genes.We analyzed immune correlations and disease correlations and performed functional annotation of the hub genes.We also performed single-cell and microenvironment analyses and investigated the enrichment pathways and the main transcription factors.Finally,we conducted a correlation analysis to evaluate the role of the hub genes.RESULTS:Interleukin 32(IL32)was identified as the hub gene in SA-AKI,and the main enriched signaling pathways were associated with hemopoiesis,cellular response to cytokine stimulus,inflammatory response,and regulation of kidney development.Additionally,IL32 was significantly associated with mortality in SA-AKI patients.Monocytes,macrophages,T cells,and NK cells were closely related to IL32 and were involved in the immune microenvironment in SA-AKI patients.IL32 expression increased significantly in the kidney of septic mouse.Toll-like receptor 2(TLR2)was significantly and negatively correlated with IL32.CONCLUSION:IL32 is the key gene involved in SA-AKI and is significantly associated with prognosis.TLR2 and relevant immune cells are closely related to key genes.

关键词： Sepsis Acute kidney injury Interleukin 32 Toll-like receptor 2 Bioinformatics analysis