The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed...The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed threedimensional misfit dislocation network, with index of （011）{100} and the side length of the mesh 89.6A, is formed around a cuboidal γ′ precipitate. Comparing the simulation results of the different mosaic models, we find that the side length of the mesh only depends on the lattice parameters of the γ and γ′ phases as well as the γ/γ′ interface direction, but is independent of the size and number of the cuboidal γ′ precipitate. The density of dislocations is inversely proportional to the size of the cuboidal γ′ precipitate, i.e. the amount of the dislocation is proportional to the total area of the γ/γ′ interface, which may be used to explain the relation between the amount of the fine γ′ particles and the creep rupture life of the superalloy. In addition, the closed three-dimensional networks assembled with the misfit dislocations can play a significant role in improving the mechanical properties of superalloys.展开更多
An Ni-AI-Co system embedded-atom-method potential is constructed for the γ（Ni）/γ＇（Ni3A1） superalloy based on experiments and first-principles calculations. The stacking fault energies （SFEs） of the Ni（Co, A1...An Ni-AI-Co system embedded-atom-method potential is constructed for the γ（Ni）/γ＇（Ni3A1） superalloy based on experiments and first-principles calculations. The stacking fault energies （SFEs） of the Ni（Co, A1） random solid solutions are calculated as a function of the concentrations of Co and A1. The calculated SFEs decrease with increasing concentrations of Co and A1, which is consistent with the experimental results. The embedding energy term in the present potential has an important influence on the SFEs of the random solid solutions. The cross-slip processes of a screw dislocation in homogenous Ni（Co） solid solutions are simulated using the present potential and the nudged elastic band method. The cross-slip activation energies increase with increasing Co concentration, which implies that the creep resistance of γ（Ni） may be improved by the addition of Co.展开更多
Using high-throughput first-principles calculations, we systematically studied the synergistic effect of alloying two elements （AI and 28 kinds of 3d, 4d, and 5d transition metals） on the elastic constants and elast...Using high-throughput first-principles calculations, we systematically studied the synergistic effect of alloying two elements （AI and 28 kinds of 3d, 4d, and 5d transition metals） on the elastic constants and elastic moduli of γ-Ni. We used machine learning to theoretically predict the relationship between alloying concentration and mechanical properties, giving the binding energy between the two elements. We found that the ternary alloying elements strengthened the 7 phase in the order of Re 〉 Ir 〉 W 〉 Ru 〉 Cr 〉 Mo 〉 Pt 〉 Ta 〉 Co. There is a quadratic parabolic relationship between the number of d shell electrons in the alloying element and the bulk modulus, and the maximum bulk modulus appears when the d shell is half full. We found a linear relationship between bulk modulus and alloying concentration over a certain alloying range. Using linear regression, we found the linear fit concentration coefficient of 29 elements. Using machine learning to theoretically predict the bulk modulus and lattice constants of Ni32XY, we predicted values close to the calculated results, with a regression parameter of R2 = 0.99626. Compared with pure Ni, the alloyed Ni has higher bulk modulus B, G, E, Cll, and C44, but equal Cl2. The alloying strengthening in some of these systems is closely tied to the binding of elements, indicating that the binding energy of the alloy is a way to assess its elastic properties.展开更多
In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is propose...In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is proposed in this paper.Two assumptions are adopted in the GBE model:(1)The displacement of grains,which moves along the perpendicular direction,is restricted by the grain boundaries;(2)Grain boundaries influence region(GBIR)is formed around the grain boundaries.Based on the single crystal(SC)calculation method of elastic properties,the GBE model can well predict macroscopic equivalent elastic modulus(Young’s modulus)of DS superalloys under different tensile orientations effectively.To demonstrate the correctness of the GBE model,3D finite element simulation is adopted and tensile experiments on a Ni3Al?base DS superalloy(IC10)along five tensile orientations are carried out.Meanwhile,the grain boundaries are observed by light microscopy and transmission electron microscope(TEM).Therefore,the GBE model is proved to be feasible by comparing the simulated results with the experiments.展开更多
基金Project supported by the State Key Development Program for Basic Research of China （Grant No G2000067102） and the National Natural Science Foundation of China （Grant No 90101004）.
文摘The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed threedimensional misfit dislocation network, with index of （011）{100} and the side length of the mesh 89.6A, is formed around a cuboidal γ′ precipitate. Comparing the simulation results of the different mosaic models, we find that the side length of the mesh only depends on the lattice parameters of the γ and γ′ phases as well as the γ/γ′ interface direction, but is independent of the size and number of the cuboidal γ′ precipitate. The density of dislocations is inversely proportional to the size of the cuboidal γ′ precipitate, i.e. the amount of the dislocation is proportional to the total area of the γ/γ′ interface, which may be used to explain the relation between the amount of the fine γ′ particles and the creep rupture life of the superalloy. In addition, the closed three-dimensional networks assembled with the misfit dislocations can play a significant role in improving the mechanical properties of superalloys.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB606402)the National Natural Science Foundation of China(Grant No.51071091)
文摘An Ni-AI-Co system embedded-atom-method potential is constructed for the γ（Ni）/γ＇（Ni3A1） superalloy based on experiments and first-principles calculations. The stacking fault energies （SFEs） of the Ni（Co, A1） random solid solutions are calculated as a function of the concentrations of Co and A1. The calculated SFEs decrease with increasing concentrations of Co and A1, which is consistent with the experimental results. The embedding energy term in the present potential has an important influence on the SFEs of the random solid solutions. The cross-slip processes of a screw dislocation in homogenous Ni（Co） solid solutions are simulated using the present potential and the nudged elastic band method. The cross-slip activation energies increase with increasing Co concentration, which implies that the creep resistance of γ（Ni） may be improved by the addition of Co.
基金Project support by the National Key R&D Program of China(Grant Nos.2017YFB0701501,2017YFB0701502,and 2017YFB0701503)
文摘Using high-throughput first-principles calculations, we systematically studied the synergistic effect of alloying two elements （AI and 28 kinds of 3d, 4d, and 5d transition metals） on the elastic constants and elastic moduli of γ-Ni. We used machine learning to theoretically predict the relationship between alloying concentration and mechanical properties, giving the binding energy between the two elements. We found that the ternary alloying elements strengthened the 7 phase in the order of Re 〉 Ir 〉 W 〉 Ru 〉 Cr 〉 Mo 〉 Pt 〉 Ta 〉 Co. There is a quadratic parabolic relationship between the number of d shell electrons in the alloying element and the bulk modulus, and the maximum bulk modulus appears when the d shell is half full. We found a linear relationship between bulk modulus and alloying concentration over a certain alloying range. Using linear regression, we found the linear fit concentration coefficient of 29 elements. Using machine learning to theoretically predict the bulk modulus and lattice constants of Ni32XY, we predicted values close to the calculated results, with a regression parameter of R2 = 0.99626. Compared with pure Ni, the alloyed Ni has higher bulk modulus B, G, E, Cll, and C44, but equal Cl2. The alloying strengthening in some of these systems is closely tied to the binding of elements, indicating that the binding energy of the alloy is a way to assess its elastic properties.
基金supported by the National Natural Science Foundation of China (No.51205190)the Fundamental Research Funds for the Central Universities (No.NS2016026)+1 种基金the Aeronautical Power Science Fund Project (No. 6141B090317)the Innovation Fund of Jiangsu Province, China (No.KYLX-0304)
文摘In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is proposed in this paper.Two assumptions are adopted in the GBE model:(1)The displacement of grains,which moves along the perpendicular direction,is restricted by the grain boundaries;(2)Grain boundaries influence region(GBIR)is formed around the grain boundaries.Based on the single crystal(SC)calculation method of elastic properties,the GBE model can well predict macroscopic equivalent elastic modulus(Young’s modulus)of DS superalloys under different tensile orientations effectively.To demonstrate the correctness of the GBE model,3D finite element simulation is adopted and tensile experiments on a Ni3Al?base DS superalloy(IC10)along five tensile orientations are carried out.Meanwhile,the grain boundaries are observed by light microscopy and transmission electron microscope(TEM).Therefore,the GBE model is proved to be feasible by comparing the simulated results with the experiments.
