The 3-sheet structure of Inconel 718 superalloy will be used in flying vehicles as heat resisting and shielding structure due to its lightweight, high strength and stiffness. The 3-sheet structure of Inconel 718 super...The 3-sheet structure of Inconel 718 superalloy will be used in flying vehicles as heat resisting and shielding structure due to its lightweight, high strength and stiffness. The 3-sheet structure of Inconel 718 superalloy processed by LBW/SPF (laser beam welding/superplastic forming) technology exhibited good configuration and uniform thickness distribution. The LBW parameters for 3-sheet structure were as follows: Pulse frequency was 32 Hz, impulse duration 3 ms, peak power per pulse 4500 W, and welding speed 180 mm/min. The SPF parameters were as follows: Temperature T=965°C, forming pressure P=4.2 MPa, and forming time t=130 min. The microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After the SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase, but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5.42% compared to 2.82% in as-weld condition. Weld metal Vickers-hardness increased from 331.63 in as-weld condition to 391.74 in post-SPF condition which was closed to the base material Vickers-hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material showed that tensile strength increased obviously and the ductility decreased slightly after SPF process. Load response test results indicated that the 3-sheet structure possessed good resistance to compression and bending load. Accordingly, the LBW/SPF technology is an appropriate forming technique for the 3-sheet structure of Inconel 718 superalloy.展开更多
Due to many remarkable physical and chemical properties,two-dimensional(2D)nanomaterials have become a hot spot in the field of condensed matter physics.In this paper,we have studied the structural,mechanical,and elec...Due to many remarkable physical and chemical properties,two-dimensional(2D)nanomaterials have become a hot spot in the field of condensed matter physics.In this paper,we have studied the structural,mechanical,and electronic properties of the 2D GaInO_(3)system by first-principles method.We find that 2D Ga InO_(3)can exist stably at ambient condition.Molecular dynamic simulations show that GaInO_(3)-sheet has excellent thermal stability and is stable up to1100 K.Electronic structural calculations show that GaInO_(3)-sheet has a band gap of 1.56 eV,which is close to the ideal band gap of solar cell materials,demonstrating great potential in future photovoltaic application.In addition,strain effect studies show that the GaInO_(3)-sheet structure always exhibits a direct band gap under biaxial compressive strain,and as the biaxial compressive strain increases,the band gap gradually decreases until it is converted into metal.While biaxial tensile strain can cause the 2D material to transform from a direct band gap semiconductor into an indirect band gap semiconductor,and even to metal.Our research expands the application of the Ga InO_(3)system,which may have potential application value in electronic devices and solar energy.展开更多
The main sources of nssSO 2- 4 and NO - 3 were summarized in this paper. By analyzing the spatial distribution features of major ions in Antarctic ice sheet and studying on the different time of the same volca...The main sources of nssSO 2- 4 and NO - 3 were summarized in this paper. By analyzing the spatial distribution features of major ions in Antarctic ice sheet and studying on the different time of the same volcanic event recorded by different ice cores from different regions in Antarctica, this paper intends to study the transmission path of nssSO 2- 4 and NO - 3. Results show that nssSO 2- 4 and NO - 3 are transmitted to the ice sheet through long distance and high altitude. The procedure of the transmission is that nssSO 2- 4 and NO - 3 are transmitted to the level between the top of troposphere and the bottom of stratosphere, then subsided to the ice sheet surface and spread to other regions.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 50672106)the Intellectual Innovation Project of the Chinese Academy of Sciences (Grant No. KJCX3-SYW.No.12)
文摘The 3-sheet structure of Inconel 718 superalloy will be used in flying vehicles as heat resisting and shielding structure due to its lightweight, high strength and stiffness. The 3-sheet structure of Inconel 718 superalloy processed by LBW/SPF (laser beam welding/superplastic forming) technology exhibited good configuration and uniform thickness distribution. The LBW parameters for 3-sheet structure were as follows: Pulse frequency was 32 Hz, impulse duration 3 ms, peak power per pulse 4500 W, and welding speed 180 mm/min. The SPF parameters were as follows: Temperature T=965°C, forming pressure P=4.2 MPa, and forming time t=130 min. The microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After the SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase, but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5.42% compared to 2.82% in as-weld condition. Weld metal Vickers-hardness increased from 331.63 in as-weld condition to 391.74 in post-SPF condition which was closed to the base material Vickers-hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material showed that tensile strength increased obviously and the ductility decreased slightly after SPF process. Load response test results indicated that the 3-sheet structure possessed good resistance to compression and bending load. Accordingly, the LBW/SPF technology is an appropriate forming technique for the 3-sheet structure of Inconel 718 superalloy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11847094,61764001,and U1404212)the Cheung Kong Scholars Programme of China+2 种基金the Program of Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT1132)Open Project of State Key Laboratory of Superhard Materials(Jilin University)China(Grant No.201703)
文摘Due to many remarkable physical and chemical properties,two-dimensional(2D)nanomaterials have become a hot spot in the field of condensed matter physics.In this paper,we have studied the structural,mechanical,and electronic properties of the 2D GaInO_(3)system by first-principles method.We find that 2D Ga InO_(3)can exist stably at ambient condition.Molecular dynamic simulations show that GaInO_(3)-sheet has excellent thermal stability and is stable up to1100 K.Electronic structural calculations show that GaInO_(3)-sheet has a band gap of 1.56 eV,which is close to the ideal band gap of solar cell materials,demonstrating great potential in future photovoltaic application.In addition,strain effect studies show that the GaInO_(3)-sheet structure always exhibits a direct band gap under biaxial compressive strain,and as the biaxial compressive strain increases,the band gap gradually decreases until it is converted into metal.While biaxial tensile strain can cause the 2D material to transform from a direct band gap semiconductor into an indirect band gap semiconductor,and even to metal.Our research expands the application of the Ga InO_(3)system,which may have potential application value in electronic devices and solar energy.
文摘The main sources of nssSO 2- 4 and NO - 3 were summarized in this paper. By analyzing the spatial distribution features of major ions in Antarctic ice sheet and studying on the different time of the same volcanic event recorded by different ice cores from different regions in Antarctica, this paper intends to study the transmission path of nssSO 2- 4 and NO - 3. Results show that nssSO 2- 4 and NO - 3 are transmitted to the ice sheet through long distance and high altitude. The procedure of the transmission is that nssSO 2- 4 and NO - 3 are transmitted to the level between the top of troposphere and the bottom of stratosphere, then subsided to the ice sheet surface and spread to other regions.
