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Effect of solidification rate on competitive grain growth in directional solidification of a nickel-base superalloy

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Science China(Technological Sciences) 2012年第5期55卷 1327-1334页

作者： zhou yizhou SUN XiaoFeng Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The mechanism of grain structure evolution during directional solidification is a fundamental subject in material science. Within the published research there exist conflicting views on the mechanism of grain overgrowth. To study the effect of solidification rate on grain structure evolution, bi-crystals samples were produced in a nickel-base superalloy at different solidification rates. It was found that at the convergent grain boundaries those grains better aligned with respect to the heat flux more readily overgrew neighbouring grains with misaligned orientations and the effect became more pronounced as solidification rate was increased. However, at diverging grain boundaries the rate of overgrowth was invariant to the solidification rate. These experimental results were compared with models in the literature. Thus, a better insight into competitive grain growth in directional solidification processes was obtained.

关键词： competitive grain growth structure evolution directional solidification nickel alloys

Effects of Homogenization Treatment on the Microsegregation of a Ni-Co Based Superalloy Produced by Directional Solidification

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Acta Metallurgica Sinica(English Letters) 2021年第7期34卷 943-954页

作者： Zijian zhou Rui Zhang Chuanyong Cui yizhou zhou Xiaofeng Sun Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

To reduce microsegregation,a series of homogenization treatments were carried out on a Ni-Co based superalloy prepared through directional solidification(DS).The element segregation characteristics and microstructural evolution were investigated by optical microscopy(OM),scanning electron microscopy(SEM),and electron probe microanalysis(EPMA).The results show that the elements are non-uniformly distributed in the solidified superalloy,in which W and Ti have the greatest tendency of ***,severe microsegregation leads to complicated precipitations,includingη-Ni_(3) Ti and eutectic(γ+γ’).EPMA results show that Al and Mo are uniformly distributed between the eutectic(γ+γ’)andγmatrix,whereas Ti is segregated in the eutectic(γ+γ’)andη*** positive segregation element Ti,which is continuously rejected into the remaining liquid duringγmatrix solidification,promotes the formation of eutectic(γ+γ’)and the transformation of theη*** to the homogenization effect,the optimal single-stage homogenization process of this alloy is 1180℃for 2 h because of the sufficient diffusion segregation of the *** the present study,a kinetic diffusion model was built to reflect the degree of element segregation during homogenization,and the diffusion coefficients of W and Ti were estimated.

关键词： Ni-Co based superalloy Element segregation Homogenization Diffusion kinetics

Portevin-Le Chatelier effect in wrought Ni-based superalloys:Experiments and mechanisms

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Journal of Materials Science & Technology 2020年第16期47卷 16-31页

作者： Chuanyong Cui Rui Zhang yizhou zhou Xiaofeng Sun Institute of Metal Research Chinese Academy of SciencesShenyang110016China

The Portevin-Le Chatelier(PLC)effect is a plastic instability in alloys at certain strain rates and deformation *** plastic instability exhibits serrated yielding in the temporal domain and strain localization in the spatial *** Ni-based superalloys often exhibit the PLC *** guarantee the safe and stable operation of equipment,it is important to study the PLC effect in wrought Ni-based *** paper provides a review of various experimental phenomena and micromechanisms related to the PLC effect in wrought Ni-based superalloys,which have been reported in various publications in recent years and include work from our own *** influences of stacking fault energy andγ’precipitates on the PLC effect in wrought Ni-based superalloys are also discussed in ***,several suggestions for the future study of the PLC effect in wrought Ni-based superalloys are provided.

关键词： PLC effect Wrought Ni-based superalloys Experimental phenomenon Micromechanism

Effects of Re on surface eutectic formation for Ni-base single crystal superalloys during directional solidification

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Journal of Materials Science & Technology 2017年第11期33卷 1308-1313页

作者： Liang Cao yizhou zhou Tao Jin Xiaofeng Sun Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Effects of Re on the formation of surface eutectics have been investigated by using Ni-base single crystal superalloys with different Re additions. It was found that Re promotes the segregation of Al and Ta to the eutectic melt, leading to an increase of the surface and internal eutectics. In addition, the addition of Re also increased the freezing range, the local solidification time, and the permeability of the dendritic network within the mushy zone. These factors ultimately promoted the outflow of the interdendritic residual liquid with the action of solidification shrinkage, and led to the formation of more surface eutectics. In contrast, the addition of Re had no obvious influence on the surface eutectic microstructures.

关键词： Surface eutectic Re addition Single crystal Superalloy

Recent advances in the stereolithographic three-dimensional printing of ceramic cores: Challenges and prospects

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Journal of Materials Science & Technology 2022年第22期117卷 79-98页

作者： Jinguo Li Xiaolong An Jingjing Liang yizhou zhou Xiaofeng Sun Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Space Manufacturing Technology(Chinese Academy of Sciences Key Laboratory) Beijing 100094China

The increasing demand for geometrically complex structures—specifically, higher-inlet-temperature turbine blades for the fifth-generation or other high-generation machines of advanced fighter aircrafts—hasmade the development of more complex double-walled three-layer hollow-cavity structures a ***, this requires the preparation of complex ceramic cores and advanced, integrated *** three-dimensional printing (SLA-3DP) technology, with digital control upon materialmorphology, composition, and structure, is a high integration and versatile technique that is superior tothe traditional manufacturing techniques for ceramic cores, including gel casting, injection molding, andhot pressing. The latent capacity of this technique is contingent on the progress of processing routesthat significantly reduce the distortion and defect formation in response to the elimination of the reactedorganic monomer phase during photo-curing. Despite the tremendous progress in the field, multiple challenges remain, such as the preparation of high-solid-content and low-viscosity suspensions, SLA-3DP oflarge double-walled ceramic cores with complex structures, and process optimization and sinter strengthening for the fabrication of ceramic cores. These challenges have prevented the broader applications andreduced the impact of the SLA-3DP technology. This review discusses cutting-edge research on the crucialfactors governing this production method. Specifically, we outline the existing challenges within the fieldand provide our perspective on the upcoming research work and progress.

关键词： Stereolithographic three-dimensional printing Ceramic cores,Cutting-edge research

Revealing the Void Formation Mechanism during Superplastic Deformation of a Fine-Grained Ni-Co-Base Superalloy

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Acta Metallurgica Sinica(English Letters) 2024年第5期37卷 915-920页

作者： Rashad AAl-Hammadi Rui Zhang Chuanyong Cui Zijian zhou yizhou zhou Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

The mechanism behind void formation during superplasticity remains a subject of *** study presented a novel insight into the void formation in a fine-grained Ni-Co-based superalloy during *** was observed that the dissolution ofγ′-particles resulted in the creation of vacancies due to differences in atomic size between the matrix and the *** vacancies acted as inclusions,leading to the formation of ***,excessive void formation correlated with higher particle dissolution was experimentally observed,highlighting a direct relationship between void formation and particle dissolution.

关键词： Superplasticity Void formation Ni-Co-based superalloy Microstructure

Microstructure and tensile properties of DD32 single crystal Ni-base superalloy repaired by laser metal forming

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Journal of Materials Science & Technology 2020年第10期42卷 23-34页

作者： Shiwei Ci Jingjing Liang Jinguo Li yizhou zhou Xiaofeng Sun Institute of Metal Research Chinese Academy of SciencesShenyang J10016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Space Manufacturing Technology(CAS Key Lab) Beijing 100094China

In this work,the microstructure and tensile properties of DD32 single-crystal(SC)superalloy repaired by laser metal forming(LMF)using pulsed laser have been studied in *** microstructures of the deposited samples and the tensile-ruptured samples were characterized by optical microscopy(OM),transmission electron microscope(TEM)and scanning electron microscope(SEM).Due to high cooling rate,the primary dendrite spacing in the deposited area(17.2μm)was apparently smaller than that in the substrate area(307μm),and the carbides in the deposited samples were also smaller compared with that in the substrate *** formation of(γ+γ’)eutectic in the initial layer of repaired SC was inhibited because of the high cooling *** the deposition proceeded,the cooling rate decreased,and the(γ+γ’)eutectic increased ***(γ+γ’)eutectic at heat-affected zone(HAZ)in the molten pool dissolved partly because of the high temperature at HAZ,but there were still residual *** test results showed that tensile behavior of repaired SC at different temperatures was closely related to the MC carbides,solidification porosity,γ’phase,and(γ+γ’)*** moderate temperature,the samples tested fractured preferentially at the substrate area due to the fragmentation of the coarse MC carbide in the substrate *** elevated temperature,the(γ+γ’)eutectic and solidification porosity in the deposited area became the source of cracks,which deteriorated the high-temperature properties and made the samples rupture at the deposited area preferentially.

关键词： DD32 Pulsed-laser Repairing Single-crystal superalloy Microstructures Tensile property

Distributed Robust Optimal Dispatch of Regional Integrated Energy Systems Based on ADMM Algorithm with Adaptive Step Size

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 852-862页

作者： zhoujun Ma yizhou zhou Yuping Zheng Li Yang Zhinong Wei the College of Energy and Electrical Engineering Hohai UniversityNanjing 211100China State Grid Jiangsu Electric Power Co. Ltd.Nanjing 210019China State Key Laboratory ofSmart Grid Protection and Control NARI Group CorporationNanjing 211106China

This paper proposes a distributed robust optimal dispatch model to enhance information security and interaction among the operators in the regional integrated energy system(RIES).Our model regards the distribution network and each energy hub(EH)as independent operators and employs robust optimization to improve operational security caused by wind and photovoltaic(PV)power output uncertainties,with only deterministic information exchanged across *** paper also adopts the alternating direction method of multipliers(ADMM)algorithm to facilitate secure information interaction among multiple RIES operators,maximizing the benefit for each ***,the traditional ADMM algorithm with fixed step size is modified to be adaptive,addressing issues of redundant interactions caused by suboptimal initial step size settings.A case study validates the effectiveness of the proposed model,demonstrating the superiority of the ADMM algorithm with adaptive step size and the economic benefits of the distributed robust optimal dispatch model over the distributed stochastic optimal dispatch model.

关键词： Regional integrated energy system(RIES) distributed optimization robust optimization operation security energy hub(EH)

Effect of C and Hf Contents on the Interface Reactions and Wettability between a Ni_3Al-Based Superalloy and Ceramic Mould Material

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Journal of Materials Science & Technology 2016年第2期32卷 177-181页

作者： Xiaoyan Chen yizhou zhou Tao Jin Xiaofeng Sun Institute of Metal Research Chinese Academy of Sciences

The influence of active elements C and Hf on the interface reactions and wettability between a Ni3Albased superalloy and the ceramic mould material was studied by using a sessile drop experiment, The microstructure of the alloy interface was investigated by scanning electron microscopy analysis and the phase identification was performed by X-ray diffraction analysis, The results show that interface reactions occur as C and Hf contents reach a critical value, The critical values for C and Hf to cause interface reactions are 0,12 wt% and 1,17 wt%, respectively, The reaction products contain HfO2 and 9Al2OH,Cr2O3, Adsorptions of Hf and interface reactions improve the wettability obviously,

关键词： Superalloys Ceramic Interface reaction Wettability C Hf