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Grain Growth Behavior of Inconel 625 Superalloy

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Journal of Iron and Steel Research International 2016年第10期23卷 1111-1118页

作者： Min LIU Wen-jie ZHenG Jin-zhong xiang Zhi-gang SONG en-xiang pu Han FenG School of Physics Science and Technology Yunnan University Kunming 650093 Yunnan China Central Iron and Steel Research Institute Beijing 100081 China School of Materials Science and engineering Tsinghua University Beijing 100084 China

The grain growth（GG）behavior of Inconel 625 superalloy was studied in the temperature range of 900-1 250 ℃and holding time range of 10-80 *** of the alloy were characterized by optical metallography,scanning electron microscopy（SEM）and transmission electron microscopy（TEM）.Grains grew obviously with either increasing temperature or extending holding time at temperatures above 1 050℃.However,at temperatures lower than 1 050 ℃,the GG was sluggish due to the pinning effect of carbide particles on grain boundary（GB）.Threshold temperature for transition from mixed grain structure to uniform one was considered to be around 1 100℃.Once the temperatures surpassed 1 200℃,an instant increase in the grain size occurred showing no dependence on holding *** analysis showed that the dominant second phase formed heterogeneously on the GB was M6 C,which significantly impeded grain *** the basis of experimental data,the mathematical model of GG was established,which can describe GG behavior of Inconel 625 alloy during solution treatment（ST）at 1 100-1 250 ℃.The activation energy for GG of Inconel 625 alloy was 207.3kJ,which suggested that the GG of Inconel 625 alloy was controlled by the process of GB diffusion.

关键词： Inconel 625 alloy growth kinetics solution treatment precipitation

Effect of Precipitation on Hot Deformation Behavior and Processing Maps of Nickel-Base UNS N10276 Alloy

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Acta Metallurgica Sinica(english Letters) 2017年第11期30卷 1119-1134页

作者： en-xiang pu Wen-Jie Zheng Zhi-Gang Song Han Feng Han Dong School of Materials Science and engineering Tsinghua University Beijing 100084 China Central Iron and Steel Research Institute Beijing 100081China

The hot deformation characteristics and processing maps of aged nickel-base UNS N10276 alloy were inves- tigated and compared with those of solution-treated UNS N10276 alloy at temperatures of 950-1250 ℃ and strain rates between 0.01 and 10 s-1. The dominant precipitated phase in the aged alloy was identified as topologically close-packed （TCP） # phase enriched in Mo and Ni. The precipitates present in the UNS N10276 alloy could significantly facilitate flow softening after peak stress at temperatures lower than 1150 ℃ and strain rates higher than 0.01 s-1. Processing maps at true strains of 0.1-0.9 were developed using the dynamic materials model and experimental flow stress data. Although aging treatment slightly shrank the suitable hot working window of this alloy, the aged alloy showed higher peak efficiencies of power dissipation and smaller unstable regions in comparison with solution-treated alloy. Furthermore, aging treatment eliminated the instability region of processing maps at true strains of 0.2-0.5. The precipitated phase promoted dynamic recrystallization （DRX） by the particle-stimulated nucleation （PSN） mechanism, which resulted in the larger fraction of DRX as well as finer and more uniform grain structure in the aged alloy specimens compared to the solution-treated alloy.

关键词： UNS N10276 alloy Precipitation Hot deformation Processing map

Optimization of Hot Workability in Superaustenitic Stainless Steel 654SMO

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Journal of Iron and Steel Research International 2014年第10期21卷 975-982页

作者： en-xiang pu Wen-jie ZHenG Zhi-gang SONG Jin-zhong xiang Xian-ping WEI School of Physics Science and Technology Yunnan University Central Iron and Steel Research Institute

Hot compression tests were conducted on a Gleeble-3800 machine in a temperature range of 950 to 1200 ℃ and a strain rate range of 0. 001 to 10 s-1 in order to study the hot deformation behaviour of superaustenitic stainless steel 654SMO. The results show that peak stress increases with decreasing temperature and increasing strain rate, and the apparent activation energy of this alloy was determined to be about 494 kJ/mol. The constitutive equation which can be used to relate the peak stress to the absolute temperature and strain rate was obtained. The processing maps for hot working developed on the basis of flow stress data and the dynamic materials model were adopted to op- timize the hot workability. It is found that the features of the maps obtained in the strain range of 0.2 to 1.0 are fun- damentally similar, indicating that the strain does not have a substantial influence on processing map. The combina- tion of processing map and mierostructural observations indicates that the favorable hot deformation conditions are located in two domains of processing map. The first domain occurs in the temperature range of 980 to 1035 ℃ and strain rate range of 0. 001 to 0.01 s-1 with a peak efficiency of 55%. The second domain appears in the temperature range of 1 120 to 1 180 ℃ and strain rate range of 0.3 to 3 s-1 with peak efficiency of 35%. Compared to other stable domains, the specimens deformed in these two domains exhibit full dynamic recrystallization grains with finer and more uniform sizes. An instability domain occurs at temperatures below 1 100 ℃ and strain rate above 0.1 s-1 , and flow instability is manifested in the form of flow localization.

关键词： 654SMO steel superaustenitic stainless steell processing mapl hot deformationl dynamic recrystallization

Constitutive Modeling for Flow Behaviors of Superaustenitic Stainless Steel S32654 during Hot Deformation

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Journal of Iron and Steel Research International 2016年第2期23卷 178-184页

作者： en-xiang pu Han FenG Min LIU Wen-jie ZHenG Han DONG Zhi-gang SONG Central Iron and Steel Research Institute Beijing 100081China School of Materials Science and engineering Tsinghua UniversityBeijing 100084China

Hot deformation behavior of superaustenitic stainless steel S32654 was investigated with hot compression tests at temperatures of 950-1250 C and strain rates of 0. 001-10 s-1. Above 1150 ℃, with strain rate lower than 0.1 s -1 , the flow curves exhibit nearly steady state behavior, while at higher strain rate, continuous flow softening occurs. To provide a precise prediction of flow behavior for the alloy, the constitutive modeling considering effect of strain was derived on the basis of the obtained experimental data and constitutive relationship which incorporated Ar- rhenius term and hyperbolic sine type equation. The material constants α, n, Q and lnA are found to be functions of the strain and can be fitted employing eighth-order polynomial. The developed constitutive model can be employed to describe the deformation behavior of superaustenitic stainless steel S32654.

关键词： S32654 superaustenitic stainless steel hot deformation constitutive modeling

Precipitation Behavior and Microstructural Evolution of Ferritic Ti–V–Mo Complex Microalloyed Steel

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Acta Metallurgica Sinica(english Letters) 2018年第9期31卷 997-1005页

作者： Ke Zhang Hui Wang Xin-Jun Sun Feng-Li Sui Zhao-Dong Li en-xiang pu Zheng-Hai Zhu Zhen-Yi Huang Hong-Bo Pan Qi-Long Yong Key Laboratory of Metallurgical Emission Reduction and Resources Recycling Anhui University of TechnologyMinistry of EducationMaanshan 243032China School of Metallurgical engineering Anhui University of TechnologyMaanshan 243032China Central Iron and Steel Research Institute Beijing 100081China

Precipitation behavior of （Ti, V, Mo）C and microstructural evolution of the ferritic Ti-V-Mo complex microalloyed steel were investigated through changing coiling temperature （CT）. It is demonstrated that the strength of the Ti-V-Mo microalloyed steel can be ascribed to the combination of grain refinement hardening and precipitation hardening. The variation of hardness （from 318 to 415 HV, then to 327 HV） with CT （from 500 to 600-625 ℃, then to 700 ℃） was attributed to the changes of volume fraction and particle size of （Ti, V, Mo）C precipitates. The optimum CT was considered as 600-625 ℃, at which the maximum hardness value （415 HV） can be obtained. It was found that the atomic ratios of Ti, V and Mo in （Ti, V, Mo）C carbides were changed as the CT increased. The precipitates with the size of 〈 10 nm were the V-rich particles at higher CT of 600 and 650 ℃, while the Ti-rich particles were observed at lower CT of 500 and 550 ℃. Theoretical calculations indicated that the maximum nucleation rate of （Ti, V, Mo）C in ferrite matrix occurred around 630 ℃, which was consistent with the 625 ℃ obtained from experiment results.

关键词： Nano-sized precipitates Precipitation hardening Ti-V-Mo Coiling temperature Ferrite

Irradiation behaviors of two novel single-phase bcc-structure high-entropy alloys for accident-tolerant fuel cladding

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Journal of Materials Science & Technology 2021年第25期84卷 230-238页

作者： Zijian Zhang en-Hou Han Chao xiang Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and engineering University of Science and Technology of ChinaShenyang110016China School of Materials Science and engineering Northeastern UniversityShenyang110819China

High-entropy alloys(HEAs)are potential alternative materials for accident-tolerant fuel cladding due to their excellent irradiation resistance and high-temperature corrosion *** this work,two novel body-centered cubic(bcc)structured Mo_(0.5)Nb Ti VCr_(0.25)and Mo_(0.5)Nb Ti V_(0.5)Zr_(0.25)HEAs were ***-ion irradiation was performed on the two HEAs to simulate neutron irradiation,and the crystal structure,hardness,and microstructure evolution were *** crystal structure of the Mo_(0.5)NbTiVCr_(0.25)HEA remained stable at low fluences,while amorphization may occur at high fluences in the two *** irradiation hardening value of the Mo_(0.5)NbTiVCr_(0.25)was 0.77 GPa at fluences of 1×10^(17)ions/cm^(2)and 1.49 GPa at fluences of 5×10^(17)ions/cm^(2),while the hardening value of the Mo_(0.5)NbTiV_(0.5)Zr_(0.25)was 1.36 GPa at ion fluences of 5×10^(17)ions/cm^(2).In comparison with most of the conventional alloys,the two HEAs showed slight irradiation *** helium bubbles and dislocation loops with small size were observed in the two HEAs after *** is the first time to report the formation of a dislocation loop in bcc-structure HEAs after ***,voids and precipitates were not observed in the two HEAs which could be ascribed to the high lattice distortion and compositional complexity of *** research revealed that the two HEAs show outstanding irradiation resistance,which may be promising accident-tolerant fuel cladding materials.

关键词： High-entropy alloy Accident-tolerant fuel cladding Helium-ion irradiation Microstructure Irradiation hardening

AVDTC Numbers of Generalized Halin Graphs with Maximum Degree at Least 6

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Acta Mathematicae Applicatae Sinica 2008年第1期24卷 55-74页

作者： xiang-en Chen Zhong-fu Zhang College of Mathematics and Information Science Northwest Normal University Lanzhou 730070 China Institute of Applied Mathematics Lanzhou Jiaotong University Lanzhou 730070 China

In a paper by Zhang and Chen et al.（see [11]）, a conjecture was made concerning the minimum number of colors Xat（G） required in a proper total-coloring of G so that any two adjacent vertices have different color sets, where the color set of a vertex v is the set composed of the color of v and the colors incident to v. We find the exact values of Xat（G） and thus verify the conjecture when G is a Generalized Halin graph with maximum degree at least 6, A generalized Halin graph is a 2-connected plane graph G such that removing all the edges of the boundary of the exterior face of G （the degrees of the vertices in the boundary of exterior face of G are all three） gives a tree.

关键词： Graph total coloring adjacent-vertex-distinguishing total coloring adjacent-vertex-distinguishing total chromatic number.

Effect of Nb Content on Microstructure and Mechanical Properties of Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nbx High-entropy Alloys

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Acta Metallurgica Sinica(english Letters) 2022年第10期35卷 1641-1652页

作者： Fengqi Zhang Chao xiang en-Hou Han Zijian Zhang Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and engineering University of Science and Technology of ChinaShenyang110016China Institute of Corrosion Science and Technology Guangzhou510530China

High-entropy alloys(HEAs)have significant application prospects as promising candidate materials for nuclear industry due to their excellent mechanical properties,corrosion resistance and irradiation *** this work,the Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x)(x=0,0.25,0.5,0.75 and 1.0)HEAs were designed and *** alloys were prepared by vacuum arc melting,and all the ingots were annealed at 1200℃ for 24 *** microstructures,crystal structures,hardness and mechanical properties of Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x) HEAs were *** as-cast alloys are composed of single BCC ***,the single BCC phase is retained after annealing at 1200℃ for 24 *** compressive and microhardness tests show that the strength and hardness of the alloys decrease gradually with the increase of Nb content,while the plasticity increases and the fracture mode of the alloy changes from brittle fracture to ductile fracture,which is mainly owing to the decrease of grain *** addition of Nb significantly improves the plasticity of the Mo_(0.25)V_(0.25)Ti_(1.5)Zr_(0.5)Nb_(x) *** particular,Nb1.0 alloy can reach 28.32%strain without fracture,which exhibits promising potential in industrial application.

关键词： High-entropy alloy CALPHAD Microstructure Hardness Mechanical properties

Optimization Design and Performance Analysis of Vehicle Powertrain Mounting System

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Chinese Journal of Mechanical engineering 2018年第2期31卷 76-88页

作者： Han Zhou Hui Liu pu Gao Chang-Le xiang School of Mechanical engineering Beijing Institute of Technology National Key Lab of Vehicular Transmission Beijing Institute of Technology

The design strategies for powertrain mounting systems play an important role in the reduction of vehicular vibration and noise. As stiffness and damping elements connecting the transmission system and vehicle body, the rubber mount exhibits better vibration isolation performance than the rigid connection. This paper presents a complete design process of the mounting system, including the vibration decoupling, vibration simulation analysis, topology optimization, and experimental verification. Based on the 6?degrees?of?freedom vibration coupling model of the powertrain mounting system, an optimization algorithm is used to extract the best design parameters of each mount, thus rendering the mounting system fully decoupled and the natural frequency well configured, and the optimal parameters are used to design the mounting system. Subsequently, vibration simulation analysis is applied to the mounting system, considering both transmission and road excitations. According to the results of finite element analysis, the topological structure of the metal frame of the front mount is optimized to improve the strength and dynamic characteristics of the mounting system. Finally, the vibration bench test is used to verify the availability of the optimization design with the analysis of acceleration response and vibration transmissibility of the mounting system. The results show that the vibration isolation performance of the mounting system can be improved effectively using the vibration optimal decoupling method, and the structural modification of the metal frame can well promote the dynamic characteristics of the mounting system.

关键词： Mounting system Optimization algorithm Vibration simulation analysis Topological structure Acceleration response Vibration transmissibility