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WEI X.-P.,Kunming University of Science and Technology | WEI X.-P.,Control Iron and Steel Research Institute, China | ZHENG W.-J.,Control Iron and Steel Research Institute, China | SONG Z.-G.,Control Iron and Steel Research Institute, China | And 3 more authors.
Journal of Iron and Steel Research International | Year: 2013

The optimization of heat treatment and chemical composition for Inconel 718 alloy has been investigated uninterruptedly because of its excellent mechanical properties and metallurgical workability. The species, chemical compositions and content of equilibrium phases of Inconel 718 alloy in the temperature range of 600-2014;1100 °C were calculated by using thermodynamic software "Thermo-Calc" and the latest relevant datebase of Ni-base superalloys. A concept of elemental partitioning fraction was used to study the partitioning characteristics of alloying elements in each equilibrium phase at different temperatures, such as Ni, Cr, Fe, Nb, Mo, Al, Ti and C, and some calculation results were confirmed under a scanning transmission electron microscope (STEM). The results showed that the elemental partitioning characteristics with the change of temperature revealed the selective partitioning characteristic of alloying elements in equilibrium phases at different temperatures, such as Nb was mainly distributed in δ and γ' phase, C in carbides, Al and Ti in γ' phase and Cr, Mo in Laves phase. At the same time, the effect of the change of component and quantity for each precipitated phase on matrix phase can be helpfully understood, which provided a theoretic foundation to optimize the chemical composition and heat treatment in different environments for Inconel 718 alloy. © 2013 Central Iron and Steel Research Institute. Source


Zheng W.-J.,Control Iron and Steel Research Institute, China | Wei X.-P.,Materials Research Center | Song Z.-G.,Control Iron and Steel Research Institute, China | Yong Q.-L.,Control Iron and Steel Research Institute, China | And 2 more authors.
Journal of Iron and Steel Research International | Year: 2015

For improving the service performance of Inconel 718 alloy, especially used as a corrosion-resistant alloy for special environment, the microstructure and mechanical property of different carbon-containing Inconel 718 alloys were investigated by the Thermo-Calc software and experiments. The experimental results indicated that the morphology, distribution and types of carbides mainly existing in the form of MC were hardly influenced by solution treatment at 1050 °C for 1 h. The precipitation amount and particle size of carbides decreased with the decrease of carbon content, which was the main reason resulting in the increase of ductility and toughness. In addition, moving dislocation could be restrained by the precipitation of carbides. Therefore, the strength could benefit from the precipitation strengthening of carbides when the precipitation of γ'/γ″ phase was not influenced by the precipitation of carbides. © 2015 Central Iron and Steel Research Institute. Source


Huang X.G.,Nanjing University of Science and Technology | Huang X.G.,Lehigh University | Yan Z.Y.,Lehigh University | Liu C.,Nanjing University of Science and Technology | And 2 more authors.
Materials Research Innovations | Year: 2015

Magnetorheological elastomer is a novel kind of magnetorheological materials. It has magnetorheological effect as well as novel electrical properties. This paper focuses on studying the characteristic of magnetorheological elastomer resistance. A resistance theory model of magnetorheological elastomer was built at first, and then the magnetoresistive characteristic and piezoresistance property of magnetorheological elastomer samples with different contents of graphite powder were tested. The test results show that the proportion of graphite powder has a significant effect on the resistance of magnetorheological elastomer. Those magnetorheological elastomers may be regarded as an insulator, since their graphite powder rate is <14%. For those magnetorheological elastomers whose graphite powder rate is >14%, the resistance value decreases with the increase of magnetic field intensity or applied load. In other words, the greater the magnetic field intensity or the applied load, the smaller the electrical resistance changes. © W. S. Maney & Son Ltd 2015. Source


Wei X.-P.,Kunming University of Science and Technology | Wei X.-P.,Control Iron and Steel Research Institute, China | Zheng W.-J.,Control Iron and Steel Research Institute, China | Song Z.-G.,Control Iron and Steel Research Institute, China | And 3 more authors.
Journal of Iron and Steel Research International | Year: 2014

To study the precipitation dynamics of δ phase in Inconel 718 alloy, two-stage interrupted compression method was used in the region of cold deformation temperatures and the temperatures range from 875 to 975 °C. The precipitation-time-temperature (PTT) curve of δ phase was obtained by analyzing the softening kinetics curves. For verifying the type of the precipitates and confirming the validity of the test, the transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersion spectrum (EDS) were employed. Experimental results indicated that the PTT curve for δ precipitation exhibited a typical "C" shape and the nose points of start and finish precipitation were about 5 s at 920 °C and 2815 s at 940 °C, respectively. In addition, the nucleation of δ was heterogeneous. The nucleation sites varied with temperatures, including dislocation, grain boundary and stacking fault within γ' phase. And δ particles grew quickly at higher temperature with lower density. Moreover, the driving force of nucleation was mainly including chemical free energy, interfacial energy and dislocation distorted energy. And the dislocation distorted energy could decide the density of nucleation in the strain-induced process. © 2014 Central Iron and Steel Research Institute. Source


Wei X.,Kunming University of Science and Technology | Wei X.,Control Iron and Steel Research Institute, China | Zheng W.,Control Iron and Steel Research Institute, China | Song Z.,Control Iron and Steel Research Institute, China | And 3 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2014

The softening behavior of Inconel 718 alloy at different temperatures was studied using two-stage interrupted compression method on Gleeble1500D thermal stimulator, and the 2% offset method was applied to analyze the experimental dates. Finally, the static recrystallization fraction was obtained. At the same times, optical microscope (OM) and transmission electron microscopy (TEM) were employed to investigate the microstructure characteristic. The experimental results showed that the recrystallization was more sensitive to temperature than holding time. The recrystallization process finished quickly above 1 050 °C, and significantly prolonged below 1 025 °C. Additionally, the dynamical model of static recrystallization follows the Avrami equation. The nucleating mechanism was characterized by bulging at grain boundary and merging of sub-grain. © 2014 Wuhan University of Technology and Springer-Verlag Berlin Heidelberg. Source

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