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Effects of Mo addition on microstructure of a 4th generation Ni-based single crystal superalloy

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Progress in Natural Science:Materials International 2022年第6期32卷 745-751页

作者： Yuan Cheng Xinbao Zhao Wanshun Xia Qinghai Pan Quanzhao Yue yuefeng gu Ze Zhang Institute of Superalloys Science and Technology School of Materials Science and Engineering Zhejiang University

The effects of Mo addition on the microstructure of a 4th generation Ni-based single crystal superalloy were investigated.Mo addition significantly promoted elements Mo,W and Re partition into γ phase and enhanced absolute lattice misfit at 1100℃.The increase of Mo concentration from 2 wt% to 4 wt% also decreased the content of eutectic islands and the segregation ratios of other alloying elements in the as-cast state,especially Re and W.After heat treatments,the size of γ' phase and width of γ channels decreased slightly with higher Mo content.More Mo additions slightly enhanced the segregation behavior of Re while reducing the segregation behavior of Mo.However,it revealed that the primary and secondary dendrite arm spacings were barely affected by Mo addition.

关键词： Ni-based single crystal superalloys Mo Segregation ratio Lattice misfit

Aging process design based on the morphological evolution ofγprecipitates in a 4th generation nickel-based single crystal superalloy

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Journal of Materials Science & Technology 2023年第16期147卷 176-188页

作者： Jiachen Xu Xinbao Zhao Weiqi Li Hao Liu Quanzhao Yue Huanchang Duan yuefeng gu Ze Zhang Institute of Superalloys Science and Technology School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027ZhejiangChina Polytechnic Institute Zhejiang UniversityHangzhou 310027ZhejiangChina

In order to meet the design requirements of the aging treatment process of a 4th generation nickel-based single crystal superalloy(Ni-SX)developed independently,the effects of aging temperatures and aging times on the precipitation and morphological evolution ofγprecipitates are studied.The morphological evolution behavior ofγprecipitates during the aging process is summarized subsequently and the coarsening behavior ofγprecipitates is discussed by comparing with the Lifshitz-Slyozov-Wagner model(LSW)and the trans-interface diffusion-controlled model(TIDC).It is demonstrated that primary aging temperature and secondary aging time dominate the size and squareness ofγprecipitates respectively,a narrow primary aging temperature range and a suitable secondary aging time are allowed to obtain the optimized morphology ofγprecipitates.The optimal aging process of the Ni-SX investigated in the present work is obtained for 1100-1120°C/4 h and 870°C/16 h,confirmed by the corresponding creep tests.The coarsening growth ofγprecipitates in short-term aging also conforms to the LSW model well.Besides,the aging process design rules of various Ni-SXs of different generations are also summarized.

关键词： Nickel-based single crystal superalloy Aging temperature Aging time γprecipitates Creep

Impacts of different designed microstructures on creep performance of a Ni-based wrought superalloy

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Progress in Natural Science:Materials International 2023年第5期33卷 625-633页

作者： Hao Liu Xinbao Zhao Yuan Cheng Jiachen Xu Shuhao Cheng Quanzhao Yue Yong Yuan yuefeng gu Ze Zhang Institute of Superalloys Science and Technology School of Materials Science and Engineering Zhejiang University Polytechnic Institute Zhejiang University State Key Laboratory of Silicon and Advanced Semiconductor Materials Zhejiang University Xi'an Thermal Power Research Institute Co.Ltd.

The creep behavior of a novel Ni-based wrought superalloy with varying aging states, classified as large underaged(UA), little UA, and little over-aged(OA) states, was investigated at a temperature higher than the intragrain/grain-boundary iso-strength temperature(750°C/250 MPa). In the samples before creep test, there are spherical γ’precipitates homogeneously dispersed within the γ matrix and carbides precipitated at grain boundaries(GBs). After creep tests, precipitate-free zones(PFZs) appear on grain boundaries, with a large blocklike γ’phase present between carbides and PFZs, potentially serving as initiation sites for cracks. Little UA state samples exhibit the strongest creep resistance and intergranular fracture. The dominant creep deformation mechanism in the intra-grain is a combination of Orowan process involving slip and climb of matrix dislocations and shearing of γ’precipitates. The results indicate that the optimizing the grain boundary microstructure may be more important than the change of intragranular microstructure when the creep temperature exceeds the isostrength temperature.

关键词： Ni-based wrought superalloy Intragranular microstructure Creep performance

Dynamic Strain Aging in a Newly Developed Ni-Co-Base Superalloy with Low Stacking Fault Energy

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Journal of Materials Science & Technology 2013年第9期29卷 873-878页

作者： Chenggang Tian Chuanyong Cui Ling Xu yuefeng gu Xiaofeng Sun Superalloys Division Institute of Metal ResearchChinese Academy of Sciences

Characteristics of dynamic strain aging （DSA） in a Ni-Co-base superalloy were studied by tensile tests at temperatures ranging from 250 ℃ to 550 ℃ and strain rates ranging from 3 x 10-5 to 8 x 10-4 s-1. Serrated flow in the tensile stress-strain curves was observed in the temperature range from 300 ℃ to 500 ℃. Normal DSA behavior was found at temperatures ranging from 300 ℃ to 350 ℃, while inverse DSA behavior was observed at temperatures ranging from 400 ℃ to 500 ℃. The yield strength, ultimate tensile strength, elongation, work hardening index, and fracture features were not affected by temperature and strain rates in DSA regime. Negative strain-rate sensitivity of flow stress was observed in DSA regime. The analysis suggests that the ordering of the substitutional solutes around some defects like mobile dislocations and stacking faults due to the thermal activated process may cause the serrations on the tensile curves.

关键词： Ni- Co base superalloy Dynamic strain aging （DSA） Activation energy Substitutional solute Stacking fault

Microstructural evolution of a Ni-Co based superalloy during hot compression atγ'sub-/super-solvus temperatures

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Journal of Materials Science & Technology 2021年第18期77卷 66-81页

作者： Peng Liu Rui Zhang Yong Yuan Chuanyong Cui Faguang Liang Xi Liu yuefeng gu 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 Xi'an Thermal Power Research Institute Co.Ltd. Xi'an 710032China

The effects of strain rate on the microstructural evolution and deformation mechanism of a Ni-Co based superalloy were investigated by isothermal compression tests performed atγ'sub-solvus(1090℃)andγ'super-solvus temperatures(1150℃)with a wide strain rate range from 0.001 to 10 s^(-1)under a true strain of 0.693.Electron backscatter diffraction(EBSD),electron channeling contrast imaging(ECCI)and transmission electron microscope(TEM)techniques were used to characterize the microstructures.The results revealed that the dynamic recrystallization(DRX)volume fraction increased and stored energy of theγ'matrix grains decreased with increasing the strain rate duringγ'sub-solvus temperature deformation,while the opposite phenomena were observed duringγ'super-solvus temperature deformation.The comprehensive effect of initial grain size,primaryγ'phase,twins and adiabatic temperature rise led to these results.The primaryγ'particles undergone the deformation behavior within itself and obviously accelerated the DRX of the matrix.The microstructural evolution proved that discontinuous dynamic recrystallization(DDRX)was the dominant mechanism during the hot deformation carried out at bothγ'sub-solvus andγ'super-solvus temperatures.Primaryγ'particles obviously accelerated the nucleation step and retarded the growth step of DDRX duringγ'sub-solvus temperature deformation.Besides,the acceleration effect of primaryγ'particles on DDRX increased with the increase of strain rate.Continuous dynamic recrystallization(CDRX)was confirmed to be an assistant mechanism duringγ'super-solvus temperature deformation and was promoted with the increase of strain rate.

关键词： Ni-Co based superalloy Strain rate Primaryγ'precipitates Dynamic recrystallization Microstructural evolution

Effect of heat treatment on the microstructure of a Ni–Fe based superalloy for advanced ultra-supercritical power plant applications

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Progress in Natural Science:Materials International 2016年第2期26卷 204-209页

作者： Xinbao Zhao Yingying Dang Hongfei Yin Jintao Lu Yong Yuan Zhen Yang Jingbo Yan yuefeng gu Xi'an Thermal Power Research Institute Co. Ltd. National Energy R&D Center of Clean and High-Efficiency Fossil-Fired Power Generation Technology

The effect of heat treatment on the microstructure and microhardness of a Ni–Fe based superalloy for700 °C advanced ultra-supercritical coalfi red power plants was investigated. Results showed that the main phases in the alloy were γ, γ′, MC and M23C6, and no harmful phase was observed in the alloy.M23C6-type carbides discretely distributed nearby grain boundaries as the alloy was aged at above840 °C. The microhardness decreased with increasing aging temperature. The coarsening of γ′ led to the increment of microhardness at 780 °C and 810 °C for a short aging time, and a signi fi cant decrease in microhardness after aging at 840 °C. The aging temperature had more signi fi cant role on the microstructure than holding time. Therefore, to obtain optimum strengthening effect for this alloy, the aging temperature should not exceed 810 °C.

关键词： Ultra-supercritical power plant Ni – Fe based superalloy Heat treatment Microstructure Microhardness

中小学生综合素质概念的历史嬗变与新时代内涵

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教育与教学研究 2024年第5期38卷 16-27页

作者：吴立宝谷越峰高博豪张永健天津师范大学教育学部天津300387 天津市第五十五中学天津300070 首都师范大学数学科学学院北京100048

挖掘中小学生综合素质概念嬗变的逻辑、深入理解新时代背景下中小学生综合素质内涵、推进中小学生综合素质评价,是深化教育评价改革、促进中国式教育现代化、实现教育强国的必然要求。梳理综合素质概念形成的历史脉络,可以划分为三个阶... 详细信息

挖掘中小学生综合素质概念嬗变的逻辑、深入理解新时代背景下中小学生综合素质内涵、推进中小学生综合素质评价,是深化教育评价改革、促进中国式教育现代化、实现教育强国的必然要求。梳理综合素质概念形成的历史脉络,可以划分为三个阶段:在概念认识的萌芽阶段,综合素质从应试教育迈向素质教育;在概念的发展阶段,综合素质从基础目标走向多元兼顾;在概念的深化阶段,综合素质从五项并举转向“五育融合”。中小学生综合素质概念嬗变的逻辑起点是教育矛盾的时代变化,嬗变的现实逻辑是社会发展的阶段跃进,嬗变的价值逻辑是人的发展不断深化。中小学生综合素质的新时代内涵具体表现为:对接世界、丰富内核,完善学生综合素质内涵;转变理念、回归初心,凸显综合素质重要价值;智能加持、打破局限,谋划综合素质的深远发展;技术赋能、开拓创新,指向综合素质模式变革。

关键词：综合素质中小学生综合素质认识嬗变素质教育

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双边货币互换和跨境资本流入“急停”

南方金融 2023年第12期 19-37页

作者：陈雷谷越峰李月琪广东金融学院广东广州510521 衢州学院浙江衢州324000

在美联储连续快速加息的背景下,非储备货币国家面临的国际流动性风险显著上升,如何防范和化解国际流动性风险成为不少国家亟待解决的难题。本文将“流动性螺旋”机制引入理论模型以刻画央行的最后贷款人行为,阐述双边货币互换对跨境资... 详细信息

在美联储连续快速加息的背景下,非储备货币国家面临的国际流动性风险显著上升,如何防范和化解国际流动性风险成为不少国家亟待解决的难题。本文将“流动性螺旋”机制引入理论模型以刻画央行的最后贷款人行为,阐述双边货币互换对跨境资本流入“急停”的影响机制,并使用覆盖范围较为广泛的跨国面板数据,实证检验双边货币互换与跨境资本流入“急停”的关系。研究结果表明:双边货币互换能够显著降低跨境资本流入“急停”发生的概率,但是这种缓解作用在全球金融风险水平较高的情形下有所减弱;双边货币互换对外商直接投资、债券组合类投资和其他类投资的跨境流入“急停”存在显著影响,对权益组合类投资的影响则不显著。上述研究结论的启示:为了防范国际流动性风险冲击,各国最有效的应对策略是维持经济持续平稳增长,并辅之以更加完善的双边货币互换制度安排;我国央行可进一步推动建立和完善与更多非储备货币国家的双边本币互换网络,在促进人民币国际化的同时,为积极应对跨境资本流动冲击、维护国际金融稳定提供“中国方案”。

关键词：国际金融双边货币互换跨境资本流动人民币国际化金融风险防控

NiFe基合金激光增材制造热裂纹形成机理及调控

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焊接学报 2022年第5期43卷 8-13,I0003,I0004页

作者：王帅付立铭袁勇尹宏飞徐济进谷月峰上海交通大学上海市激光制造与材料改性重点实验室上海200240 上海交通大学上海200240 西安热工研究院有限公司西安710032

针对NiFe基高温合金增材制造过程易出现热裂纹的问题,开展该合金热裂纹形成机理的研究,提出通过层间温度控制以及粉末氮化的方法,降低NiFe基高温合金激光增材过程中的热裂纹敏感性.结果表明,热裂纹的出现主要是由于元素偏析以及热应力... 详细信息

针对NiFe基高温合金增材制造过程易出现热裂纹的问题,开展该合金热裂纹形成机理的研究,提出通过层间温度控制以及粉末氮化的方法,降低NiFe基高温合金激光增材过程中的热裂纹敏感性.结果表明,热裂纹的出现主要是由于元素偏析以及热应力所引发的,热裂纹位置大多在大角度晶界处,这是由于大角度晶界中能量较高,在冷却过程中,晶界内液膜的存贮时间较长,从而造成偏析加剧.当层间温度较低,冷却速度加快,能够减少合金中有害碳化物的长大,降低了大角度晶界比例,从而抑制热裂纹的出现.粉末预氮化通过预先将Ti, Nb等元素进行氮化,形成稳定氮化物,在抑制开裂敏感性元素偏析的同时增加了形核点,促进晶粒细化,从而降低该合金的热裂纹敏感性.

关键词： NiFe基高温合金增材制造热裂纹层间温度粉末氮化