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Stability of γ′ multimodal microstructure in a Ni-based powder metallurgy superalloy

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Science China(Technological Sciences) 2018年第12期61卷 1824-1828页

作者： ZHANG Ming LIU GuoQuan WANG Hao hu benfu School of Materials Science and Engineering University of Science and Technology Beijing

Multimodal size distribution of γ′ phase was obtained in a slow-cooling experiment following supersolvus solution treatment(1191°C). The morphology of the secondary γ′ particles exhibited splitting and protrusion instabilities. In the subsequent aging process(815°C), reverse coarsening was observed, i.e., the average precipitate size decreased with increasing aging *** coarsening slows the coarsening rate of the precipitates, increases the hardness of the alloy, and greatly improves the morphological stability of the γ′ phase.

关键词： Nickel alloys γ′ phase multimodal size distribution microstructure stability

Microstructure Stability of V and Ta Microalloyed 12%Cr Reduced Activation Ferrite/Martensite Steel during Long-term Aging at 650℃

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Journal of Materials Science & Technology 2015年第3期31卷 311-319页

作者： Xiang Xiao Guoquan Liu benfu hu Jinsan Wang Wenbin Ma School of Materials Science and Engineering University of Science and Technology Beijing Chinalco Research Institute of Science and Technology Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing

In view of developing novel alloys for applications in supercritical water-cooled reactor fuel cladding and in-core components, a 12%Cr reduced activation ferrite/martensite(RAFM) steel with good corrosion resistance and irradiation performance was developed. V and Ta were added to form fine MX type carbonitrides and enhance the high temperature creep rupture strength. Microstructure stability of the steel during long-term aging at 650 C was studied experimentally combined with the simulation of ThermoCalc and DICTRA software. The results show that the precipitates in the steel during long-term aging contain M23C6, MX and Laves phase. M23C6 carbides play a major role in the stabilization of the tempered martensite lath structure by exerting a large Zener pinning force as compared with MX and Laves *** V and Ta in the steel can not only promote MX precipitation, but also refine M23C6 carbides and thus improve the thermal stability of lath/subgrains, which is beneficial to the improvement of high temperature microstructure stability of the 12%Cr RAFM steel.

关键词： 12%Cr reduced activation ferrite/martensite steel

Cooling γ′ precipitation behavior and strengthening in powder metallurgy su-peralloy FGH4096

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Rare Metals 2008年第4期27卷 410-417页

作者： TIAN Gaofeng JIA Chengchang WEN Yin LIU Guoquan hu benfu School of Materials Science and Engineering University of Science and Technology Beifing Beifing 100083 China

Two cooling schemes （continuous cooling and interrupted cooling tests） were applied to investigate the cooling γ precipitation behavior in powder metallurgy superalloy FGH4096. The effect of cooling rate on cooling γ precipitation and the development of γ precipitates during cooling process were involved in this study. The ultimate tensile strength （ErrS） of the specimens in various cooling circumstances was tested. The experiential equations were obtained between the average sizes of secondary and tertiary γ precipitates, the strength, and cooling rate. The results show that they are inversely correlated with the cooling rate as well as the grain boundary changes from serrated to straight, the shape of secondary γ precipitates changes from irregular cuboidal to spherical, while the formed tertiary γ precipitates are always spherical. The interrupted cooling tests show that the average size of secondary γ precipitates increases as a linear function of interrupt temperature for a fixed cooling rate of 24℃/min. The strength first decreases and then increases against interrupt temperature, which is fundamentally caused by the multistage nucleation of γ precipitates during cooling process.

关键词： nickel-base superalloy powder metallurgy (P/M) γ precipitates cooling rate heat treatment

Hot deformation behavior of FGH96 superalloys

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Journal of University of Science and Technology Beijing 2006年第4期13卷 319-323页

作者： Jiantao Liu Guoquan Liu benfu hu Yuepeng Song Ziran Qin Yiwen Zhang Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 Chin High Temperature Material Institute Central Iron ＆ Steel Research Institute Beijing 100081 China

The hot deformation behavior of FGH96 superalloys at 1070-1170℃ and 5×10^-4-2×10^-1 s^-1 were investigated by means of the isothermal compression tests at a Gleeble-1500 thermal mechanical simulator. The results show that dynamic recovery acts as the main softening mechanism below 2×10^-3 s^-1, whereas dynamic recrystallization acts as the main softening mechanism above 2× 10^-3 s^-1 during deformation; the temperature increase caused by the deformation and the corresponding softening stress is negligible; the thermal-mechanical constitutive model to describe the hot deformation behavior is given, and the value of the apparent deformation activation energy （Qdef） is determined to be 354.93 kJ/mol.

关键词： FGH96 superalloys hot deformation hot deformation activation energy dynamic recovery dynamic recrystallization

Effect of Ta on the microstructure of high performance Ni-based powder metallurgy superalloys

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Science China(Technological Sciences) 2019年第11期62卷 1961-1967页

作者： WANG ZhiCheng WANG Hao LIU GuoQuan huANG HaiLiang ZHANG HongFei SHAO YinLong hu benfu School of Materials Science and Engineering University of Science and Technology Beijing

The effect of Ta on the microstructures of nickel-based powder metallurgy superalloys with different Ta contents was investigated in experiments and thermodynamic calculations. The Ta element predominantly occupied the γ′ phase of the superalloys, with some incursion into the γ phase, and minimal presence in the MC carbide. By substituting part of the Ti-Nb alloy,the Ta element transforms(Ti-Nb)C into(Ti-Ta-Nb)C. The MC carbides and small amounts of M23C6 carbides were observed on the ribbon-like grain boundaries. The Ta addition little affected the primary γ′ phase, but greatly influenced the secondary γ′phase. Ta promoted the splitting of the secondary γ′ phase, converting it to a more stable state. Increasing the Ta content increased the lattice constants of γ′ and γ and altered the degree of misfit between γ′ and γ, indicating a morphology change. The Ta content also influenced the formation of the tertiary γ′ phase.

关键词： superalloy powder metallurgy microstructure carbides γ'

Relationship between Low Temperature Toughness and Microstructure in Low Activation Fe-Cr-Mn(W,V)Steel for Fusion Reactors

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International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 111-115页

作者： benfu hu Chengchang jia(Material Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China) Material Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

Fe-Cr-Mn (W, V) austenite steel was researched in order to supply a theory base for the first wall materials of fusion *** included vacuum melting, forging, annealing, solution treatment, Charpy impact tests and microstructure observation. Theresults show that the imped value decreases with the test temperature decreasing. In this system, there is ductile/brittle transition. Themechanism of this decrease of the impact value is considered to be due to γ - ε transformation in sub-stable austenite steel and stoppingoverlapping sacking fault by grain boundaries in stable austenite steel.

关键词： fusion reactor first wall materials low temperature toughness Fe-Cr-Mn system

Irradiation Damage of Oxide Dispersion Strengthened Ferritic Steel after Recrystallization

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 160-164页

作者： benfu hu Shunmi Peng H Takahashi(Material Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China)(Faculty of Engineering, Hokkado University, Sapporo 060, Japan) Material Science and Engineering School University of Science and Technology Beijing Beijing 100083 China Faculty of Engineering Hokkado University Sapporo 060 Japan

The evolution of secondary defects and the characteristics of the void swelling of electrons irradiated Oxide Dispersion Strengthened Ferritic Steels (ODS steels) after recrystallization were studied. It was found that recrystallization increases the void swelling of ODS steel as compared with solution and injected He+ + D+ *** are two size ranges of voids formed in recrystallized ODS steel during irradiation, and bubbles can be preferential sites for the void formation. Polycrystal with low density of defects is formed, and sites where point defects disappear by irradiation decrease. This is the main reason for the increase of void swelling of ODS steel after recrystallization.

关键词： ODS steel recrystallization, electron irradiation

拓扑密堆μ相对含Hf的镍基粉末高温合金组织和性能的影响

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金属学报 2016年第4期52卷 445-454页

作者：张义文胡本芙钢铁研究总院高温材料研究所北京100081 钢铁研究总院高温合金新材料北京市重点实验室北京100081 北京科技大学材料科学与工程学院北京100083

研究了含Hf（0~0.89%）的FGH4097粉末高温合金中拓扑密堆μ相的析出动力学、组织形态以及μ相对Hf含量为0.30%的合金盘坯力学性能的影响.结果表明,Hf含量为0.30%和0.89%的合金,经750~900℃长期时效后μ相已明显析出.随着时效温度的升高... 详细信息

研究了含Hf（0~0.89%）的FGH4097粉末高温合金中拓扑密堆μ相的析出动力学、组织形态以及μ相对Hf含量为0.30%的合金盘坯力学性能的影响.结果表明,Hf含量为0.30%和0.89%的合金,经750~900℃长期时效后μ相已明显析出.随着时效温度的升高、时效时间的延长以及Hf添加量的增加,μ相析出量增加且尺寸长大.μ相主要在晶内以长条片状形态析出.Hf含量为0.30%的FGH4097合金盘坯在550~650℃长期时效后未出现μ相,高温拉伸性能和高温持久性能没有降低,组织稳定性良好.750℃长期时效后,盘坯中析出了μ相,析出的μ相对高温拉伸强度无明显影响,有助于提高高温拉伸塑性,降低了高温持久寿命,高温持久塑性提高约30%.详细讨论了μ相的析出行为、g固溶体中合金元素的再分配以及合金断口特征.解释了μ相对力学性能影响的脆-韧双重作用机理,并提出控制和避免μ相大量析出造成性能劣化的措施和方法.

关键词：粉末高温合金 FGH4097 Hf μ相力学性能

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镍基粉末高温合金中微量元素Hf的作用

金属学报 2015年第8期51卷 967-975页

利用FEG-SEM,TEM,AES和EDS分析技术以及物理化学相分析等方法,系统地研究了微量元素Hf在镍基粉末高温合金中的作用.结果表明:Hf以固溶态分布在枝晶间γ固溶体内,有助于减少原始粉末颗粒边界组织.Hf促进γ′相形态失稳,导致大尺寸立方状... 详细信息

利用FEG-SEM,TEM,AES和EDS分析技术以及物理化学相分析等方法,系统地研究了微量元素Hf在镍基粉末高温合金中的作用.结果表明:Hf以固溶态分布在枝晶间γ固溶体内,有助于减少原始粉末颗粒边界组织.Hf促进γ′相形态失稳,导致大尺寸立方状γ′相发生分裂,更快地进入γ′相低能稳定的择优形态.Hf主要分布在γ′相和MC型碳化物中,改变γ′相和MC型碳化物及γ固溶体相间合金元素的再分配,有利于消除合金的缺口敏感性,改善合金综合力学性能.

关键词：粉末高温合金 Hf,MC型碳化物 γ′相的形态稳定性原始粉末颗粒边界