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Microstructure and Elevated Temperature Tensile Behavior of Directionally Solidified Ni-rich NiAl-Mo(Hf) Alloy

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Journal of Materials Science & Technology 2011年第5期27卷 437-442页

作者： Ping Han Yihui Qi jianting guo Department of Physics Bohai University Jinzhou 121013 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The microstructure, high strain rate superplasticity and tensile creep behavior of directionally solidified （DS） NiAI-Mo（Hf） alloy have been investigated. The alloy exhibits dendritic structure, where dendritic arm is NiAI phase, interdendritic region is Ni3AI phase, and Mo-rich phase distributes in the NiAI and Ni3AI phases. The alloy exhibits high strain rate superplastic deformation behavior, and the maximum elongation is 104.2% at 1373 K and strain rate of 1.04xi0-2 s-I. The balance between strain hardening （by dislocation glide） and strain softening （by dynamic recovery and recrystallization） is responsible for the superplastic deformation. All the creep curves of the DS NiAI-Mo（Hf） alloy have similar shape of a short primary creep and dominant steady creep stages, and the creep strain is great. The possible creep deformation mechanism was also discussed. The creep fracture data follow the Monkman-Grant relationship.

关键词： NiA1 alloy Directional solidification Superplasticity Creep

Microstructural Stability of a Multiphase Ni-25Al-15Cr (at. pct) Intermetallic Alloy

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Journal of Materials Science & Technology 1999年第2期15卷 133-136页

作者： Chen, Rongshi guo, jianting Zhou, Jiyang Chinese Acad Sci Inst Met Res Dept Superalloys Shenyang 110015 Peoples R China Dalian Univ Technol Dept Mat Engn Dalian 116023 Peoples R China

The microstructure of multiphase Ni-25Al-15Cr (at. pct) intermetallic alloy consists of dendritic arms ( beta -NiAl phase) and interdendritic regions ( gamma / gamma ' two phases) under homogenization followed by air cooling condition. Furnace cooling following homogenization does not significantly influence its microstructure. However, the effects of aging treatment on the microstructure strongly depend on cooling rates following homogenization. A single phase gamma ' layer with a alpha Cr spouse layer was observed surrounding the dendritic arms, the formation of this couple is attributed to a four-phase invariant quasi-peritectoid. (Edited author abstract) 16 Refs.

关键词： Nickel alloys

Effect of Heat Treatment on the Microstructure of Multiphase NiAl-based Alloy

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Journal of Materials Science & Technology 2008年第2期24卷 245-250页

作者： Yi XIE Lanzhang ZHOU jianting guo Hengqiang YE Superalloys Division Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

The alloy Ni-Al26.6-Cr13.4-Co8.1-Ti4.3-W1.3-Mo0.9 （at. pct） was fabricated from superalloy K44 and Al element using vacuum induction and casting technique. Investigations to this alloy reveal that a new phase Cr3Ni2 possessing low melting point and poor ductility is formed, which is distributed as a network along NiAI matrix grain boundaries. Subsequent different solution and aging treatments are carried out and lead to microstructural changes to various extents. Rapid cooling after solution at 1250℃ for 20 h gives rise to macrocracks in the specimen while slow cooling after the same treatment results in the formation of spheric α-Cr solid solution and needle-like Ni3Al phase, which are embedded in NiAl matrix. It is comfirmed that aging treatments initiate lath-shaped Ni3Al phase and pearl-shaped α-Cr phase to precipitate from the NiAl matrix, which own orientation relationships with these precipitates.

关键词： NiAl Intermetallics Microstructure Solution and aging treatments

High Temperature Creep and Fracture Behavior of a Directionally Solidified Ni-base Superalloy

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Journal of Materials Science & Technology 1998年第3期14卷 219-225页

作者： Yuan, Chao guo, jianting Wang, Shuhe Yang, Hongcai Acad Sinica Inst Met Res Shenyang 110015 Peoples R China Northeastern Univ Dept Mat Sci & Engn Shenyang 110006 Peoples R China

The tensile creep-fracture properties of DZ17G, a directionally solidified superalloy, were investigated at 830-900 degree C. The results show that all of the creep curves exhibit negligible primary creep, relatively little steady-state creep and dominant tertiary creep stage. The higher apparent activation energy for creep (540 kJ/mol) suggests that the creep is controlled by Orowan bowing process. A large ratio of the fracture time to the onset time of tertiary creep is the consequence of microstructure change, i.e., gamma ' particles oriented coarsening parallel to the applied stress axis. The creep fracture data follow the Monkman-Grant relationship. The transgranular fracture mechanism proposed on the basis of the metallographic examinations is the linkage of the creep cracks which initiate at the discontinuities with the microstructure (such as the cast porosity, and the carbide/matrix interface) and also at the specimen surface, that propagate along the gamma / gamma ' interface with perpendicular to the applied stress axis, and the process of crack propagation can be described by the Tien model. (Edited author abstract) 31 Refs.

关键词： Nickel alloys

Thermal Stability of a New Ni-Fe-Cr Base Alloy with Different Ti/Al Ratios

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Journal of Materials Science & Technology 2015年第2期31卷 135-142页

作者： Changshuai Wang Tingting Wang Meilin Tan Yongan guo jianting guo Lanzhang Zhou Institute of Metal Research Chinese Academy of Sciences

Influence of Ti/Al ratios on the thermal stability of a new low cost Ni-Fe-Cr base wrought alloy,designed for application at 700℃ in advanced ultra-supercritical coal-fired power plants(700℃A-USC),was investigated both experimentally and thermodynamically. After standard heat treatment,the alloys with different Ti/Al ratios had the same microstructural characteristics. However,compared with the alloys with high Ti/Al ratio,the low Ti/Al ratio can increase the γ’-solvus temperature,decrease γ’ coarsening rate and reduce the temperature range of η phase precipitation. For the alloys with low Ti/Al ratio,the yield strength has no obvious decrease during long-term thermal exposure at 700 and 750℃,but after thermal exposure at 750℃ for 5000 h,the yield strength of the alloys with high Ti/Al ratio obviously decreases due to the η phase precipitation. The influence of h phase on mechanical properties is related with its size. When the h phase is small,it has no obvious influence on mechanical properties,but h phase becomes the crack initiation site with the further growth of η phase. It can be concluded that the decrease in Ti/Al ratio can improve the thermal stability to meet the requirement of 700℃ A-USC coal-fired power plants.

关键词： 700℃ A-USC Ni-Fe-Cr base alloy Thermal stability η

Effect of 0.1 wt pct Dy Addition on Morphology and Compressive Behavior of Cast ***-0.2Hf

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Journal of Materials Science & Technology 2006年第2期22卷 179-182页

作者： Qiang GAO jianting guo Kaiwen HUAI Hutian LI Junshan ZHANG Department of Materials Engineering Dalian University of Technology Dailian 116024 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China

Effect of 0.1 wt pct Dy addition on microstructure and compressive behavior of NiAl-28Cr-5.8Mo-0.2 Hf eutectic alloy was investigated. The results showed that remarkable lamellar refinement can be achieved with the addition of 0.1 wt pct Dy. The Dy addition results in the decrease in Young＇s modulus of alloy and *** of the compressive strength and ductility of alloy at all testing temperatures. The lamellar refinement, the increased dislocation networks located at the interfaces of NiAl/Cr（Mo） and the strengthening of cell boundary are benefical to the improvement of compressive properties of the alloy.

关键词： NiAl-28Cr-5.8Mo-0.2Hf Dy Microstructure Compressive properties

Effect of Nb on the Microstructure and Mechanical Properties of Cast NiAl-Cr(Mo) Eutectic Alloy

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Journal of Materials Science & Technology 2006年第2期22卷 164-168页

作者： Kaiwen HUAI jianting guo Zirong REN Qiang GAO Rui YANG Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Department of Chemistry Engineering Anshan University of Science and Technology Anshan 114002 China

The microstructure and mechanical behaviors of NiAl-28Cr-5Mo-1Nb eutectic alloy were investigated by using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and compression tests, respectively. The alloy is mainly composed of three phases, which are the gray lamellar Cr（Mo） plate, black NiAI matrix and semicontinuously distributed Cr2Nb-type Laves phase. Through Nb addition, NiAl-Cr（Mo）/Nb alloy exhibits a reasonable balance of high temperature strength and room temperature compression ductility and its mechanical behaviors are superior to the NiAl-28Cr-6Mo eutectic alloy at all temperature. The elevated temperature compression deformation behavior of NiAl-Cr（Mo）/Nb alloy can be properly described by power-law *** National High Technology Committee of China （No. 863-715-005-0030） for financial supports.

关键词： NiAl-28Cr-51Mo-1Nb Microstructure Nb(Cr1-x-yNizAly)2 phase Mechanical properties Elevated temperature deformation mechanisms

Effect of hot isostatic pressing on microstructure of cast gas-turbine vanes of K452 alloy

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Progress in Natural Science:Materials International 2014年第4期24卷 631-636页

作者： Jie Li Chao Yuan jianting guo Jieshan Hou Lanzhang Zhou Institute of Mental Research Chinese Academy of Sciences

The effect of hot isostatic pressing(HIP) treatment on microstructure of gas-turbine vanes made of K452 alloy was investigated by OM,SEM and TEM. The results showed that HIP treatment played a great role in the porosity healing processing, where 80% of porosities were eliminated and the diameter of remnant porosities decreased to 10 μm. The healing mechanism of the porosities was consistent with existing theories of porosity closure based on vacancy diffusion. According to the result of the tensile test, the plasticity of the alloy was improved as the result of the elimination of the porosities and the improvement of dendritic segregation, while there was not an obvious improvement in the tensile strength after the programmed HIP process. In addition, HIP had a positive effect on narrowing down the dispersion of tensile properties.

关键词： Nickel-based superalloy K452 Hot isostatic pressing Microstructure Tensile properties

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Formation Mechanism of NiAl/TiB_2 Nanocomposite by Mechanical Alloying Elemental Powders

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Journal of Materials Science & Technology 1998年第6期14卷 491-496页

作者： Lanzhang ZHOU and jianting guo(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China) Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

A NiAl/TiB2 nanocomposite is synthesized by mechanical alloying elemental powders. Upon milling for a certain time, an abrupt exothermic reaction occurs and a large amount of NiAl and TiB2 compounds form simultaneously. It is suggested that two separate chemical reactions,i.e. Ni+Al →NiAl and Ti+2B→TiB2, are involved during the exothermic reaction. Additionof Ti and B to Ni-Al system impedes the structural evolution of Ni and Al powders and delays the abrupt reaction. The final products are equilibrium phases without any metastable phases formed. This type of reaction is suggested to be suitable for alloy systems with two large heatrelease reactions.

关键词： NiAl TiB Formation Mechanism of NiAl/TiB2 Nanocomposite by Mechanical Alloying Elemental Powders