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Characterization and numerical simulation of nucleation-growth-coarsening kinetics of precipitates in G115 martensitic heat resistance steel during long-term aging

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Journal of Iron and Steel Research(International) 2023年第6期30卷 1279-1290页

作者： Yun-he Yu Zheng-dong Liu Zhen Liu Zheng-zong Chen han-sheng bao Chi Zhang Zhi-gang Yang Shagang School of Iron and Steel Soochow UniversitySuzhou 215137JiangsuChina Key Laboratory for Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Research Institute of Special Steels Central Iron and Steel Research InstituteBeijing 100081China

The service performance of heat resistance steels is largely determined by the precipitation kinetics.The nucleation-growth-coarsening behaviors of precipitates in G115 martensitic heat resistance steel during long-term aging at 650℃ have been systemically investigated.The microstructural characteristics,precipitate morphology and alloying element distribution were studied by scanning electron microscopy,transmission electron microscopy and scanning transmission electron microscopy.The lognormal distribution fitting combined with the multiple regression analysis was adopted to evaluate the precipitate size distributions.Laves phase has longer incubation time,and its coarsening rate is almost one order of magnitude higher in comparison with that of M_(23)C_(6) carbide.Furthermore,the nucleation rate,number density,average radius,and volume fraction of two precipitates are simulated based on the classical nucleation theory and the modified Langer-Schwartz model.The precipitation behavior of Laves phase can be well explained with the Fe-W system as the interfacial energy takes 0.10 J/m^(2).In contrast,the simulation results of M_(23)C_(6) carbide in the Fe-Cr-C system are significantly overestimated,which results from the inhibitory effect of boron on coarsening.

关键词： Nucleation Growth Coarsening Precipitation kinetics G115 heat resistance steel Long-term aging

Effects of long term aging on microstructure and properties of a tungsten bearing heat resistant alloy

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Journal of Iron and Steel Research(International) 2020年第4期27卷 477-487页

作者： han-sheng bao Gang Yang Zheng-zong Chen Zheng-dong Liu Institute for Special Steels Central Iron and Steel Research InstituteBeijing 100081China

The effects of long-term aging at 700 and 750℃ on microstructure and mechanical properties of a new developed tungsten bearing heat-resistant alloy used for advanced ultra-supercritical power plant was investigated both experimentally and thermodynamically.Experimental results showed that the mechanical properties maintained excellent stability after long-term aging at 700℃ for 10,000h,while the impact absorbing energy decreased sharply after 1000-h aging and then kept constant till 10,000h.The main precipitates after long-term aging at 700 and 750℃ were M23C6,MC and homogeneous γ′-phases.The mass fraction of M23C6 carbides increased with increasing aging time,and M23C6 carbides precipitated in shape of chains and lamellas on grain boundaries.The slight decrease in MC carbides during aging may be due to degradation reaction.The weight fraction of γ′-phase increased with the aging time,and then changed little after 5000h;γ′-phase exhibited excellent microstructure stability and low coarsening rate during long-term aging at 700℃.However,the coarsening rate of γ′-phase was much higher at 750℃.

关键词： Tungsten Long-term aging Heat-resistant alloy gama′-phase Coarsening rate

Evolution of precipitates in Ni-Co-Cr-W-Mo superalloys with different tungsten contents

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Rare Metals 2020年第6期39卷 716-724页

作者： han-sheng bao Zhi-Hua Gong Zheng-Zong Chen Gang Yang Institute for Special Steels Central Iron and Steel Research InstituteBeijing 100081China School of Materials and Metallurgy Inner Mongolia University of Science and TechnologyBaotou 014010China

The Ni-Co-Cr-W-Mo system is critical for the design of nickel-based superalloys.This system stabilizes different topologically close-packed(TCP)phases in many commercially superalloys with high W and Mo contents.Scanning electron microscopy(SEM),transmission electron microscopy(TEM)and thermodynamic calculations were applied to investigate the thermodynamics of the precipitates in two different W-contained Ni-Co-Cr-WMo superalloys(Alloy 1 and Alloy 2).Computational thermodynamics verifies the experimental observation of theμphase formation as a function of temperature and alloy chemistry,but the kinetics for the precipitation of the M6 C phase do not agree with the experimental findings.The major precipitates of Alloy 1 at temperatures of700℃and 750℃during long-time exposure are M23 C6,γ′phase and MC;for Alloy 2,they are M23 C6,γ′phase,MC,M6 C andμphase.W addition is found to promote the precipitation of M6 C andμphase during exposure.M6 C has higher W and lower Ni content thanμphase,whereas M6 C is an unstable phase that would transform into M12 C after 5000-h exposure at 750℃.A great quantity of needle-likeμphases precipitated after exposure at 750℃for5000 h,which have no effect on the impact properties of Alloy 2.

关键词： Nickel-based superalloys M6C μphase Long-time exposure M12C

Effect of W on formation and properties of precipitates in Ni-based superalloys

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Journal of Iron and Steel Research(International) 2021年第7期28卷 910-919页

作者： Zhi-hua Gong Yuan-yuan Ma han-sheng bao Gang Yang Inner Mongolia University of Science and Technology Baotou 014010Inner MongoliaChina Institute for Special Steels Central Iron and Steel Research InstituteBeijing 100081China

The formation and properties of precipitates in wrought Ni-based superalloys with different W contents during long-term exposure to high temperatures were investigated.The scanning electron microscope,transmission electron microscope,and chemical phase analysis were used to investigate the formation and properties of precipitates.It is found that with increasing W content,the quantity and thermal stability of MC carbide in Ni-based superalloys increased,while the quantity of M_(23)C_(6)carbides decreased.As the results show,W has a higher partition coefficient in γ'-and γ-matrix,and the addition of W promotes the precipitation of γ'phase.W content has no significant effect on the morphology,size,crystal structure,and coarsening rate of γ'precipitates.The influence of W content on high-temperature tensile and creep properties of the alloys was investigated.The results showed that W content has no obvious influence on the high-temperature yield strength,but the elongation and area reduction decreased significantly when the addition of W was more than 4 wt.%.Because of the similar volume fractions of γ'phase,the creep fracture strengths in the tested alloys with lower W concentrations were not significantly different after long-term exposure at 700℃.

关键词： Ni-based superalloy W content Waspaloy alloy Heat resistance MC carbide

Microstructural evolution and mechanical properties of a new Ni-based heat-resistant alloy during aging at 750℃

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Journal of Iron and Steel Research(International) 2017年第5期24卷 513-519页

作者： Zhong-liang Tian Sen-bao Jiang Zheng-zong Chen han-sheng bao Zheng-dong Liu Institute for Special Steels Central Iron and Steel Research Institute College of Material Science & Engineering Taiyuan Science & Technology University

Microstructural evolution and mechanical properties of a new candidate Ni-based heat-resistant alloy for advanced ultra-supercritical （A-USC） steam turbine rotors were investigated during aging at 750℃ up to 10000 h. The evolutions of γ＇ particles inside austenitic grain and M_23 C_6 carbides along grain boundaries were characterized according to their morphologies, distributions, and growth kinetics. Mean radius of the γ＇ spherical particles grew from 20.3 to 90.0 nm after aging for 10000 h, and;the corresponding coarse- ning behavior was conformed to the law of Lifschitz-Slyosovd-Wagner （LSW）. The weight fraction of γ＇ particles slightly increased from 10.0 to 12.0 wt. % after aging of long duration at 750 ℃.The Cr-rich M_23C_6 carbides discontinuously precipitated along grain boundaries, while other detrimental phases were not formed during the aging treatment, and hence the strength of grain boundary was enhanced by these discontinuously distributed carbides. The critical size of γ＇ had a direct influence on the maximum hardness of this alloy. Moreover, this alloy presented a good impact toughness for the safety after long time aging at high temperature.

关键词： Aging Precipitation Microstruetural evolution Mechanical property Heat-resistant alloy

Impacts of multiple laser shock processing on microstructure and mechanical property of high-carbon steel

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Journal of Iron and Steel Research(International) 2018年第4期25卷 469-475页

作者： Yi Xiong Tian-tian He Yan Lu han-sheng bao Yong Li Feng-zhang Ren Wei Cao Alex A. Volinsky School of Materials Science and Engineering Henan University of Science and Technology Luoyang 471023 Henan China Collaborative Innovation Center of Nonferrous Metals Luoyang 471023 Henan China Institute for Special Steels Central Iron and Steel Research Institute Beijing 100081 China Nano and Molecular Systems Research Unit University of Oulu 90014 Oulu Finland School of Mechanical and Automotive Engineering Anhui Polytechnic University Wuhu 241000 Anhui China Department of Mechanical Engineering University of South Florida Tampa FL 33620 USA

Multiple laser shock processing （LSP） impacts on microstructures and mechanical properties were investigated through morphological determinations and hardness testing. Microscopic results show that without equal channel angular pressing （ECAP）, the LSP-treated lamellar pearlite was transferred to irregular ferrite matrix and incompletely broken cementite particles. With ECAP, LSP leads to refinements of the equiaxed ferrite grain in ultrafine-grained microduplex structure from 400 to 150 nm, and the completely spheroidized cementite particles from 150 to 100 nm. Consequentially, enhancements of mechanical properties were found in strength, microhardness and elongations of samples consisting of lamellar pearlite and ultrafine-grained microduplex structure. After LSP, a mixture of quasi-cleavage and ductile fracture was formed, different from the typical quasi-cleavage fracture from the original lamellar pearlite and the ductile fracture of the microduplex structure.

关键词： Laser shock processing High-carbon steel Ultrafine-grained microduplex structure Mechanical property

Energy saving analysis for CO_(2)–O_(2)mixed injection technology in converter steelmaking

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Journal of Iron and Steel Research(International) 2024年第5期31卷 1095-1103页

作者： bao-chen han Chun-liang Gao Ya-qiang Li Dan Liu Guang-sheng Wei Rong Zhu Hebei Key Laboratory of Material Near-Net Forming Technology School of Material Science and EngineeringHebei University of Science and TechnologyShijiazhuang050018HebeiChina Department of Automotive Engineering Hebei Vocational University of Technology and EngineeringXingtai054000HebeiChina School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China

Energy-saving in China's iron and steel industry still relies on the development and improvement of short-term energy saving technologies.Therefore,a special converter smelting technology incorporating energy saving was proposed.To evaluate the energy-saving potential of the CO_(2)–O_(2)mixed injection(COMI)technology,collected production data were used to develop an improved techno-economic model.Calculations reveal that the technology can save energy through auxiliary material consumption,sensible heat of solid by-product,iron loss reduction,and energy recovery.The application of COMI technology in an enterprise is cost effective,involving the energy saving potential of 0.206 GJ/t,the cost of conserved energy of−48.83 yuan/GJ,and a simple payback period of 0.35 year for a 60-million-yuan investment.Sensitivity analysis shows that the investment cost and discount rate primarily influence the cost of conserved energy of the technology.As the discount rate increased,the cost of conserved energy also gradually increased.Overall,the COMI technology is an energy-saving technology with good development prospects.

关键词： Converter steelmaking COMI technology Energy saving Techno-economic model Investment cost

Hybrid tri-memristor hyperchaotic map and application in Wasserstein Generative Adversarial Nets

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Science China(Technological Sciences) 2024年第6期67卷 1855-1865页

作者： GU Yang bao han YU XiHong HUA ZhongYun bao BoCheng XU Quan School of Microelectronics and Control Engineering Changzhou UniversityChangzhou213159China School of Computer Science and Technology Harbin Institute of TechnologyShenzhen518055China

Inspired by basic circuit connection methods,memristors can also be utilized in the construction of complex discrete chaotic systems.To investigate the dynamical effects of hybrid memristors,we propose two hybrid tri-memristor hyperchaotic(HTMH)mapping structures based on the hybrid parallel/cascade and cascade/parallel operations,respectively.Taking the HTMH mapping structure with hybrid parallel/cascade operation as an example,this map possesses a spatial invariant set whose stability is closely related to the initial states of the memristors.Dynamics distributions and bifurcation behaviours dependent on the control parameters are explored with numerical tools.Specifically,the memristor initial offset-boosting mechanism is theoretically demonstrated,and memristor initial offset-boosting behaviours are numerically verified.The results clarify that the HTMH map can exhibit hyperchaotic behaviours and extreme multistability with homogeneous coexisting infinite attractors.In addition,an FPGA hardware platform is fabricated to implement the HTMH map and generate pseudorandom numbers(PRNs)with high randomness.Notably,the generated PRNs can be applied in Wasserstein generative adversarial nets(WGANs)to enhance training stability and generation capability.

关键词： memristor hybrid tri-memristor map spatial invariant set hyperchaos extreme multistability generative adversarial nets

Temperature-controlled DCP Fluorescent Probe Based on Hydrogel-immobilized Quantum Dots Composite

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Journal of Wuhan University of Technology(Materials Science) 2024年第4期39卷 931-936页

作者：童伊琳杨坤 han Xuecai YU Kan bao Jiaqi Faculty Information Science and Technology Wenhua CollegeWuhan 430074China State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan 430074China Yangtze Optical Fibre and Cable Joint Stock Limited Company Wuhan 430074China

A composite was created by incorporating the quantum dot-enhanced SiO_(2)nanoparticles within this hydrogel.Based on this composite,a temperature-controlled fluorescent probe for DCP was developed.A meticulous examination of this probe revealed its attributes and factors affecting its performance.By using temperature modulation,the probe was adept at detecting DCP concentrations ranging between 1.0×10^(-6)and 9.0×10^(-6)mol/L.Such a probe offers remarkable selectivity,repeatability,and robust stability,so that the detection of DCP can be carried out at different temperatures,and a fast,reliable,sensitive and low-cost intelligent detection method is realized.

关键词： temperature-controlled fluorescent probe hydrogel-immobilized quantum dots composite DCP