The effects of annealing temperature and grit blasting pressure on the recrystallization behavior of a Ni3Al based single crystal superalloy were studied in this work. The results show that the precipitation of the Y-...The effects of annealing temperature and grit blasting pressure on the recrystallization behavior of a Ni3Al based single crystal superalloy were studied in this work. The results show that the precipitation of the Y-NiMo phase occurs at 900 and 1000 °C, which precedes recrystallization. The initial recrystallization temperature was between 1000 and 1100 °C. Cellular recrystallization was formed at 1100 and 1200 °C, which consisted of large columnar γ′ and fine γ + γ′. The dendrite arm closed to the interdendritic region may act as nucleation sites during initial recrystallization by a particle simulated nucleation mechanism at 1280 °C. The size of the grains first turned large and then became small upon the pressure while the recrystallization depth increased all the time.展开更多
Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stre...Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.展开更多
An investigation of transient liquid phase (TLP) diffusion bonding of a Ni 3Al base directionally solidified superalloy, IC6 alloy, was presented. The interlayer alloy employed was Ni Mo Cr B powder alloy. The results...An investigation of transient liquid phase (TLP) diffusion bonding of a Ni 3Al base directionally solidified superalloy, IC6 alloy, was presented. The interlayer alloy employed was Ni Mo Cr B powder alloy. The results show that the microstructure of the TLP diffusion bonded joints is a combination of γ solid solution (or a γ+γ′ structure) and borides. With the bonding time increasing, the quantity of the borides both in bonding seam and adjacent zones is gradually reduced, and the joint stress rupture property is improved. The obtained stress rupture property of the TLP bonded joints is on a level with the transverse property of IC6 base materials. [展开更多
A model system consisting of Ni[001]（100）/Ni3Al[001]（100） multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation ...A model system consisting of Ni[001]（100）/Ni3Al[001]（100） multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation results are consistent with the experimental observation that rafted Ni-base superalloys virtually possess a cubic symmetry. The convergence of the elastic properties with respect to the thickness of the multilayers are tested by a series of multilayers from 2γ′＋2γto 10γ′＋10γ atomic layers. The elastic properties are found to vary little with the increase of the multilayer＇s thickness. A Ni/Ni3Al multilayer with 10γ′＋10γ atomic layers （3.54 nm） can be used to simulate the mechanical properties of Ni-base model superalloys. Our calculated elastic constants, bulk modulus, orientation-dependent shear modulus and Young＇s modulus, as well as the Zener anisotropy factor are all compatible with the measured results of Ni-base model superalloys R1 and the advanced commercial superalloys TMS-26, CMSX-4 at a low temperature. The mechanical properties as a function of the γ′ phase volume fraction are calculated by varying the proportion of the γ and γ′ phase in the multilayers. Besides, the mechanical properties of two-phase Ni/Ni3Al multilayer can be well predicted by the Voigt-Reuss-Hill rule of mixtures.展开更多
Using first-principles calculations in combination with Wagner–Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in L12 γ-Ni3Al were inves...Using first-principles calculations in combination with Wagner–Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in L12 γ-Ni3Al were investigated. The formation energies of the point defects and the migration energies for solutes were calculated. Adding alloying elements can decrease the defect-formation energies of NiAl, increase the defect-formation energies of AlNi, and have little effect on the formation energy of VNi. The migration energies of solutes are related with the site preference and the diffusion mechanism. The diffusion coefficients of Ni, Al, and solutes were calculated, and the concentration of antisite defects plays a crucial role in the elemental diffusion.展开更多
基金supported by National Natural Science Foundation of China (No. 50971005)
文摘The effects of annealing temperature and grit blasting pressure on the recrystallization behavior of a Ni3Al based single crystal superalloy were studied in this work. The results show that the precipitation of the Y-NiMo phase occurs at 900 and 1000 °C, which precedes recrystallization. The initial recrystallization temperature was between 1000 and 1100 °C. Cellular recrystallization was formed at 1100 and 1200 °C, which consisted of large columnar γ′ and fine γ + γ′. The dendrite arm closed to the interdendritic region may act as nucleation sites during initial recrystallization by a particle simulated nucleation mechanism at 1280 °C. The size of the grains first turned large and then became small upon the pressure while the recrystallization depth increased all the time.
文摘Investigation has been made into the causes of cracking in the Surfacing welding layer of Ni3Al based alloy by analysing both the liqu id-to-solid transformation in the molten pool and the distribution of thermal stress within the surfacing welding layer. The results show that cracking in the surfacing welding layer is directly related to the producing of eutectic phase β' (NiAl) in the interdendritic region and high thermal stress within the surfacing welding layer. When the process of electric arc surfacing welding is changed from along straight line to along' Z' pattern, cracking in the surfacing welding layer of Ni3Al based alloy is prevented due to being reduced of both the cooling rate of liquid in the molten pool and the moving speed of the heat source. Reducing the melting volume of the substrate material by lowering the output power of electric arc welding would make the content of iron atoms in the molten pool decrease. and this also can reduce the trend of the eutectic reaction in the interdendfitic region and is helpful to Suppress cracking in the surfacing welding layer.
文摘An investigation of transient liquid phase (TLP) diffusion bonding of a Ni 3Al base directionally solidified superalloy, IC6 alloy, was presented. The interlayer alloy employed was Ni Mo Cr B powder alloy. The results show that the microstructure of the TLP diffusion bonded joints is a combination of γ solid solution (or a γ+γ′ structure) and borides. With the bonding time increasing, the quantity of the borides both in bonding seam and adjacent zones is gradually reduced, and the joint stress rupture property is improved. The obtained stress rupture property of the TLP bonded joints is on a level with the transverse property of IC6 base materials. [
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB605102)
文摘A model system consisting of Ni[001]（100）/Ni3Al[001]（100） multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation results are consistent with the experimental observation that rafted Ni-base superalloys virtually possess a cubic symmetry. The convergence of the elastic properties with respect to the thickness of the multilayers are tested by a series of multilayers from 2γ′＋2γto 10γ′＋10γ atomic layers. The elastic properties are found to vary little with the increase of the multilayer＇s thickness. A Ni/Ni3Al multilayer with 10γ′＋10γ atomic layers （3.54 nm） can be used to simulate the mechanical properties of Ni-base model superalloys. Our calculated elastic constants, bulk modulus, orientation-dependent shear modulus and Young＇s modulus, as well as the Zener anisotropy factor are all compatible with the measured results of Ni-base model superalloys R1 and the advanced commercial superalloys TMS-26, CMSX-4 at a low temperature. The mechanical properties as a function of the γ′ phase volume fraction are calculated by varying the proportion of the γ and γ′ phase in the multilayers. Besides, the mechanical properties of two-phase Ni/Ni3Al multilayer can be well predicted by the Voigt-Reuss-Hill rule of mixtures.
基金Project supported by Beijing Municipality Science and Technology Commission,China(Grant No.D161100002416001)the National Key R&D Program of China(Grant No.2017YFB0701502)
文摘Using first-principles calculations in combination with Wagner–Schottky and kinetic Monte Carlo methods, the diffusion behaviors of solutes via various vacancy-mediated diffusion mechanisms in L12 γ-Ni3Al were investigated. The formation energies of the point defects and the migration energies for solutes were calculated. Adding alloying elements can decrease the defect-formation energies of NiAl, increase the defect-formation energies of AlNi, and have little effect on the formation energy of VNi. The migration energies of solutes are related with the site preference and the diffusion mechanism. The diffusion coefficients of Ni, Al, and solutes were calculated, and the concentration of antisite defects plays a crucial role in the elemental diffusion.
