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Zhang Y.,Control Iron and Steel Research Institute, China | Zhang Y.,Beijing Key Laboratory of Advanced High Temperature Materials | Li K.,Control Iron and Steel Research Institute, China | Li K.,Beijing Key Laboratory of Advanced High Temperature Materials
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2016

Mixed powder was prepared by adding Al2O3 particles with different size into high temperature alloy powder sized 50-100 μm in diameter. Such mixed powder was treated by electrostatic separation (ESS) with different processing parameters and the treated powder was observed under stereoscope to determine removing effects of Al2O3 particles. The results show that the removing effect is enhanced with increasing electrical corona electrode voltage and decreasing rotating rates of drum. The ideal removing effect is obtained under electrical corona electrode voltage of 40 kV and drum rotating rates of 50 r/min, which shows that ESS can effectively remove 76% of Al2O3 particles under 200 μm and 83.3% of Al2O3 particles in the range of 100-150 μm in diameter. Mechanical analysis of single Al2O3 particle shows that ESS has different removing effects on Al2O3 particles with different size. There exists an optimum Al2O3 particles size dc, and the maximum Al2O3 particles size of 200 μm for the removing effect. It is confirmed by the calculation and experiment that the relationship between dc and dmax is dc=2/3dmax. © 2016, Editorial Office of Materials Science and Engineering of Powder Metallurgy. All right reserved.


Wang M.,Control Iron and Steel Research Institute, China | Wang M.,Tsinghua University | Wang M.,Beijing Key Laboratory of Advanced High Temperature Materials | Du J.,Control Iron and Steel Research Institute, China | And 5 more authors.
Journal of Alloys and Compounds | Year: 2017

Some research showed that the precipitation of η-Ni3Al0.5Nb0.5 phase at grain boundary can optimize the mechanical properties and reduce the notch sensitivity of the nickel-based superalloy ATI 718Plus. Therefore, finding the optimum concentration and morphology of η-Ni3Al0.5Nb0.5 for different operating conditions is of great importance during the microstructure design process. In this study, the relationship between the mechanical properties as well as notch sensitivity and the η-Ni3Al0.5Nb0.5 content in ATI 718Plus was investigated by subjecting the alloy to different heat treatment processes. The stress rupture life of ATI 718Plus was found to improve significantly by decreasing the η-Ni3Al0.5Nb0.5 content. However, the notch sensitivity drastically increased when the η-Ni3Al0.5Nb0.5 mass percentage dropped below approximately 1.1 wt%. The microstructure of the samples was analyzed by field emission scanning electron microscopy and the phase composition was quantitatively determined by electrolytic phase isolation followed by a micro-chemical and X-ray diffraction analysis. The atomic distribution of elements in the alloy on a nanoscale was determined by 3DAP technique. The phase diagram and time-temperature-transformation curve of the different phase were calculated using the JMatPro6.0 software. Furthermore, the precipitation kinetics of the η-Ni3Al0.5Nb0.5 and γ′ phases and the optimum η-Ni3Al0.5Nb0.5 mass percentage in 718Plus were discussed. © 2017 Elsevier B.V.


Wang M.,Control Iron and Steel Research Institute, China | Wang M.,Tsinghua University | Wang M.,Beijing Key Laboratory of Advanced High Temperature Materials | Deng Q.,Control Iron and Steel Research Institute, China | And 5 more authors.
Materials Transactions | Year: 2015

In this reported study, the influence of aluminum concentration on the microstructure and mechanical properties of alloy ATI 718Plus was investigated. The experimental results revealed that the content of aluminum has a significant effect on the solvus temperature and the chemical compositions of the γ′ and δ phases of ATI 718Plus. The experimental data showed that an increased concentration of aluminum in the alloy caused the tensile strength to increase, but had a negative impact on the metal's ductility. The distribution of aluminum in the matrix and phases of the alloy were systematically examined using the atom probe tomography (APT) technique. The precipitation of phases in the alloy resulting from heat treatment was predicted using the JMatPro 6.0 software application and the predicted results were verified experimentally using electrolytic phase separation followed by microchemical analysis. In addition, a more detailed analysis of the size distribution of the γ′ and crystal structure of the δ phase in the alloy was performed using SEM and XRD analysis. A full discussion of the effects of aluminum content on the mechanism of the generation of the alloy microstructure and evolution of the tensile properties is included in this report. © 2015 The Japan Institute of Metals and Materials.


Wang M.,Control Iron and Steel Research Institute, China | Wang M.,Tsinghua University | Wang M.,Beijing Key Laboratory of Advanced High Temperature Materials | Du J.,Control Iron and Steel Research Institute, China | And 5 more authors.
Materials Science and Engineering A | Year: 2015

Since the discovery in the 1990s of the abnormal improvement produced by phosphorus in the stress rupture and creep life of Inconel 718 (hereafter referred to as 718), a great deal of additional research followed. However, the mechanism of the action of phosphorous in 718 is still in question. This paper details an experimental study that was intended to determine how phosphorus acts upon the microstructure and mechanical properties of Ni-Fe based alloy 718Plus. The results show that phosphorus has little effect on the strength and ductility of alloy 718Plus, but can significantly improve the stress rupture life. Phase constituents such as the δ and γ' phases were quantitatively analyzed using electrolytic phase isolation and micro-chemical and XRD analysis as the phosphorous content of the alloy was increased. A full atom mapping of the distribution of phosphorus in the 718Plus alloy was quantitatively determined using APT (Atom Probe Tomography) technique. The results showed that there is no significant segregation of phosphorus at the γ'/γ and γ'/γ' interface, but it significantly segregates at the grain boundaries and δ/γ interface. It was found that phosphorus is extremely depleted in the δ phase, which is believed to inhibit δ-phase precipitation by preventing δ phase nucleation and growth in the 718Plus alloy. Finally, the influence of phosphorus on the microstructure and mechanical properties of the 718Plus alloy was discussed. © 2015 Elsevier B.V.


Bi Z.,Control Iron and Steel Research Institute, China | Bi Z.,Beijing Key Laboratory of Advanced High Temperature Materials | Qu J.,Control Iron and Steel Research Institute, China | Du J.,Control Iron and Steel Research Institute, China | Zhang J.,Control Iron and Steel Research Institute, China
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2013

The cast microstructure of a new difficult-to-deform superalloy zk151, was observed by high resolution field emission scanning electron microscope. The effects of elements on the thermodynamic equilibrium phases were studied by Thermo-Calc software. The results show that there is serious segregation of Mo, Nb and Ti during the solidification, which promotes γ'+γ eutectic. The main precipitates of zk151 alloy are a large fraction of cubic γ', some carbides, borides and μ phase. Higher Cr, Mo, Nb and Ti contents can improve the primary and final melting points. The contents of Al, Ti and Nb can influence the precipitation temperature and mass fraction of γ' phase. Contents of Cr and Mo promote precipitation of M23C6 and M6C respectively. Furthermore, the increment of Cr, Mo and W content leads to more precipitation of μ phase.


Yu H.,Beijing Key Laboratory of Advanced High Temperature Materials | Yu H.,Control Iron and Steel Research Institute, China | Bi Z.,Control Iron and Steel Research Institute, China | Tang C.,Control Iron and Steel Research Institute, China
Jinshu Rechuli/Heat Treatment of Metals | Year: 2016

Effects of Ti and Ta content on equilibrium precipitation of new Co-based high temperature alloy containing Cr were studied in the temperature range of 500-1500 ℃ by using PandatTM software and Co-based database. The precipitation in the alloy containing Ti or Ta was observed by means of SEM. The results show that a great number of the fine γ' phase precipitates from two-kinds of Co-based alloys containing Ti and Ta after aging at 750 ℃ for 100 h, which has a good strengthening effect. Both the mole fractions of γ' phase and μ phase increase with Ti content increasing. But only the mole fraction of γ' phase increase with Ta content increasing. The window of hot deformation in Co-based superalloy containing Ta is wider than that of Co-based superalloy containing Ti, and the segregation tendency of the former during solidification is lower than that of the latter. © 2016, Editorial Office of "Jinshu Rechuli". All right reserved.


Wang J.-T.,Control Iron and Steel Research Institute, China | Wang J.-T.,Beijing Key Laboratory of Advanced High Temperature Materials | Han W.,Control Iron and Steel Research Institute, China | Luo H.-L.,Control Iron and Steel Research Institute, China | Li S.-P.,Control Iron and Steel Research Institute, China
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2014

Two-step homogenization treatment was conducted for MX246A alloy and the homogenized microstructure was observed by scanning electron microscope (SEM). The tensile properties of as-cast and homogenized MX246A alloy were tested at 850°C and 1100°C. The results show that comparing with as-cast alloy, the ductility of homogenized MX246A alloy at 1100°C is improved, but at 850°C the ductility is reduced. A large amount of M6C carbides surrounded by γ' envelope precipitate is around interdendritic and grain boundary for homogenized MX246A alloy. During the tensile process, cracks can originate around the carbides and propagate along the carbide/-γ' envelope interface. The poor toughness of γ' envelope and poor ductility of homogenized MX246A alloy at 850°C are due to the stress concentration caused by the carbides can not be released.


Xia T.,Control Iron and Steel Research Institute, China | Xia T.,Beijing Key Laboratory of Advanced High Temperature Materials | Zhang Y.-W.,Control Iron and Steel Research Institute, China | Zhang Y.-W.,Beijing Key Laboratory of Advanced High Temperature Materials | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2014

Four experimental FGH96 alloys with various contents of Hf and Zr (0 and 0.04%, 0.3% and 0.04%, 0.6% and 0.04%, 0.3% and 0.06%, respectively) were produced using PREP (plasma rotating electrode process) + HIP (hot isostatic pressing) route. The unnotched and notched stress-rupture properties and fatigue crack growth rate (FCGR) of all the experimental alloys were investigated to study the effect of Hf and Zr. Relevant fracture morphology and microstructure were observed by scanning electron microscopy and transmission electron microscopy. The results revealed that appropriate content of Hf could lengthen stress-rupture life, eliminate notch sensitivity and slower FCGR. Microstructure analysis showed that the amount of γ' phase should be increased or decreased by adjusting Hf and Zr contents, and MC carbide and oxide coupled growth should be increased by adding Hf content, which caused oxycarbide to precipitate along grain boundary and strengthen the alloy. It was found that excessive Zr in Hf-containing FGH96 alloy had certain deleterious effects on stress-rupture property because there was strong Zr segregation at prior particle boundary, leaving a long chain of large-size oxides along the boundary. The optimal content of Hf and Zr in FGH96 alloy was 0.6% and 0.04%, respectively. © 2014 Central Iron and Steel Research Institute.


Zhang Y.-W.,Control Iron and Steel Research Institute, China | Zhang Y.-W.,Beijing Key Laboratory of Advanced High Temperature Materials | Han S.-B.,Control Iron and Steel Research Institute, China | Han S.-B.,Beijing Key Laboratory of Advanced High Temperature Materials | And 3 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2016

The partition behavior of hafnium (Hf) among different phases in FGH4097 powder metallurgy (PM) superalloy with different Hf additions and its effects on the precipitation behavior of γ′ phase, MC carbide and γ phase were studied by means of 3DAP, FEG-SEM, TEM and physiochemical phase analysis. The results show, that with increasing Hf addition, the contents of Hf in different phases increase, the mass fraction of Hf in γ′ phase almost keeps unchanged, the mass fraction of Hf in MC carbide increases and that in γ matrix decreases, which means that the partition ratio of Hf between γ′ phase and MC carbide decreases while the ratio between γ′ phase and γ matrix increases. Mass content of Hf partitioned to γ′ phase is much more than that partitioned to MC carbide, while the mass concentration of Hf in carbide is as much as 20 times of that in γ′ phase. © 2016, Central South University of Technology. All right reserved.


Xia T.,Control Iron and Steel Research Institute, China | Xia T.,Beijing Key Laboratory of Advanced High Temperature Materials | Zhang Y.,Control Iron and Steel Research Institute, China | Chi Y.,Control Iron and Steel Research Institute, China
Fenmo Yejin Jishu/Powder Metallurgy Technology | Year: 2013

FGH96 superalloy produced by PERP+HIP with various Hf and Zr contents was studied in this paper. The Hf, Zr amount was designed as 0.0+0.04%, 0.3%+0.04%, 0.6%+0.04% and 0.3%+0.06%. Optical microscope(OM) and second electricon microscope(SEM) were employed to investigate microstructures and fracture surfaces. The tested mechanical properties were listed as follows: room temperature(RT) and 800°C impact, RT, 650°C and 750°C tensile, and 650°C/970MPa unnotched/notched(R=0.15 mm) stress rupture. The results show that precipitations at PPB of FGH96 alloy can not form continuous films and hardly has destructive effects to the alloy. PPB are eliminated, elevated temperature properties are improved as well as stress rupture life and plasticity are especially enhanced with appropriate amount of Hf. While the alloy includes Hf, excess Zr lead to a continuous oxdie precipitations along the PPB, which severely degrade its endurance property. The optimum content of Hf, Zr in FGH96 alloy is 0.6%, 0.04%.

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