The microelasticity field was incorporated into the microscopic phase-field equation for the ternary alloy systems, the morphology evolution and coarsening behavior of the Ni75AixV25-x alloy were simulated. The γ pha...The microelasticity field was incorporated into the microscopic phase-field equation for the ternary alloy systems, the morphology evolution and coarsening behavior of the Ni75AixV25-x alloy were simulated. The γ phase precipitates initially for Ni75Al7aV17.9 and Ni75Al5.5V19.5 alloys and the two phases transform from the equiaxed or strip-like to the quadrate as the growth and coarsening processes. For the anisotropic elasticity interaction of the system, the orientation of γ is along the 〈001〉 directions and the θ phase is along the short axis direction of [10]. Analysis of the structure and the pair-correlation functions indicate that the average precipitate length scale of the particles increases at the late-stage coarsening, and the dynamical scaling behavior is obeyed.展开更多
The interphase boundary evolution of ordered phase in Ni75AlxV25-x alloy during precipitation was simulated on atomic-scale based on the microscopic phase-field dynamic model. The results show that the second phase pr...The interphase boundary evolution of ordered phase in Ni75AlxV25-x alloy during precipitation was simulated on atomic-scale based on the microscopic phase-field dynamic model. The results show that the second phase precipitated from the interphase boundary formed by the first phase and the disordered matrix at high temperature, and from the interphase boundaries of the first phase at low temperature. L12 phase had obvious selective orientation when precipitated from the interphase boundaries of D022- L12 phase nucleated easily at the interphase boundaries formed by [10] and [01] directions of D022 projection along [001] direction, and grew easily at [10] direction. There was no the selective orientation when L12 phase precipitated from the interphase boundary formed by D022 and the disordered matrix. D022 phase had the selective orientation when precipitated from the interphase boundaries of L12, and grew along the [10] direction.展开更多
The coarsening behavior of L12 and D022 in Ni75AlxV25-x （x,at.%） alloys including coherent strain was investigated using the microscopic phase-field model. The simulation results indicate that the shape transition a...The coarsening behavior of L12 and D022 in Ni75AlxV25-x （x,at.%） alloys including coherent strain was investigated using the microscopic phase-field model. The simulation results indicate that the shape transition and spatial correlation of L12 and D022 are caused by the morphological-dependent anisotropic elastic interactions in the system. The coarsening process of the particles is by means of neighbor particles impingement and aggregation into larger ones. For the strain-induced interactions between the precipitates,the LSW theory is altered for the coarsening behavior of L12 and D022. In addition,the simulation reveals that the growth and coarsening of D022 present two obvious stages at lower Al concentration regions and proceed simultaneously at high Al concentration regions. The growth and coarsening processes of L12 at the same regions is reverse to those of D022.展开更多
Based on the microscopic phase-field dynamic model and the microelasticity theory,the coarsening behavior of L12 and DO22 phases in Ni75CrxAl25-x alloy was simulated.The results show that the initial irregular shaped,...Based on the microscopic phase-field dynamic model and the microelasticity theory,the coarsening behavior of L12 and DO22 phases in Ni75CrxAl25-x alloy was simulated.The results show that the initial irregular shaped,randomly distributed L12 and DO22 phases are gradually transformed into cuboidal shape with round corner,regularly aligned along directions[100]and[001],and highly preferential selected microstructure is formed during the later stage of precipitation.The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics,and there is no linear relationship between the cube of the average size of precipitates and the aging time,which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner.The coarsening processes of L12 and DO22 phases are retarded in elastically constrained system.In the concurrent system of L12 and DO22 phases,there are two types of coarsening modes:the migration of antiphase domain boundaries and the interphase Ostwald ripening.展开更多
The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as...The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as the study object. With the progressive aging mechanisms, the metastable phase γ′ of high temperature can be obtained from the low temperature two phase regions, and the quantity of γ′ phase reduces with increasing temperature. The θ single phase morphology at high temperature regions will turn to be the γ′＋θ two phase morphology at low temperature with the interrupted aging method. Despite of the different precipitation paths of γ′ phase, the precipitation mechanisms are the same for the low temperature aging and high temperature interrupted aging.展开更多
Based on the microscopic phase-field model, the structure and migration characteristic of ordered domain interfaces formed between DO22 and L12 phase are investigated, and the atomistic mechanism of phase transformati...Based on the microscopic phase-field model, the structure and migration characteristic of ordered domain interfaces formed between DO22 and L12 phase are investigated, and the atomistic mechanism of phase transformation from L12 （Ni3Al） to DO22 （Ni3V） in Ni75AlxV25-x alloys are explored, using the simulated microstructure evolution pictures and the occupation probability evolution of alloy elements at the interface. The results show that five kinds of heterointerfaces are formed between DO22 and L12 phase and four of them can migrate during the phase transformation from L12 to DO22 except the interface （002）D//（001）L. The structure of interface （100）D//（200）L and interface （100）D//（200）L·^1/2[001] remain the same before and after migration, while the interface （002）D//（002）L is formed after the migration of interface （002）D//（002）L·^1/2[100] and vice versa. These two kinds of interface appear alternatively. The jump and substitute of atoms selects the optimization way to induce the migration of interface during the phase transformation, and the number of atoms needing to jump during the migration is the least among all of the possible atom jump modes.展开更多
基金This study was financially supported by the National Natural Science Foundation of China (No.50671084), the National High-TechResearch and Development Program of China (No.2002AA331050), and the Doctorate Foundation of Northwestern PolytechnicalUniversity (No.CX200507).
文摘The microelasticity field was incorporated into the microscopic phase-field equation for the ternary alloy systems, the morphology evolution and coarsening behavior of the Ni75AixV25-x alloy were simulated. The γ phase precipitates initially for Ni75Al7aV17.9 and Ni75Al5.5V19.5 alloys and the two phases transform from the equiaxed or strip-like to the quadrate as the growth and coarsening processes. For the anisotropic elasticity interaction of the system, the orientation of γ is along the 〈001〉 directions and the θ phase is along the short axis direction of [10]. Analysis of the structure and the pair-correlation functions indicate that the average precipitate length scale of the particles increases at the late-stage coarsening, and the dynamical scaling behavior is obeyed.
基金This work was financially supported by the National Nat-ural Science Foundation of China(Grant No.50071046)the Hi-tech Research and Development Program of China(Grant No.2002AA331051).
文摘The interphase boundary evolution of ordered phase in Ni75AlxV25-x alloy during precipitation was simulated on atomic-scale based on the microscopic phase-field dynamic model. The results show that the second phase precipitated from the interphase boundary formed by the first phase and the disordered matrix at high temperature, and from the interphase boundaries of the first phase at low temperature. L12 phase had obvious selective orientation when precipitated from the interphase boundaries of D022- L12 phase nucleated easily at the interphase boundaries formed by [10] and [01] directions of D022 projection along [001] direction, and grew easily at [10] direction. There was no the selective orientation when L12 phase precipitated from the interphase boundary formed by D022 and the disordered matrix. D022 phase had the selective orientation when precipitated from the interphase boundaries of L12, and grew along the [10] direction.
基金the National Natural Science Foundation of China (No. 50071046)the Hi-tech Research and Development Program of China (No. 2002AA331050)the Doctorate Foundation of Northwestern Poly-technical University (No. CX200507).
文摘The coarsening behavior of L12 and D022 in Ni75AlxV25-x （x,at.%） alloys including coherent strain was investigated using the microscopic phase-field model. The simulation results indicate that the shape transition and spatial correlation of L12 and D022 are caused by the morphological-dependent anisotropic elastic interactions in the system. The coarsening process of the particles is by means of neighbor particles impingement and aggregation into larger ones. For the strain-induced interactions between the precipitates,the LSW theory is altered for the coarsening behavior of L12 and D022. In addition,the simulation reveals that the growth and coarsening of D022 present two obvious stages at lower Al concentration regions and proceed simultaneously at high Al concentration regions. The growth and coarsening processes of L12 at the same regions is reverse to those of D022.
基金Project(50671084)supported by the National Natural Science Foundation of ChinaProject(20070420218)supported by ChinaPostdoctoral Science Foundation
文摘Based on the microscopic phase-field dynamic model and the microelasticity theory,the coarsening behavior of L12 and DO22 phases in Ni75CrxAl25-x alloy was simulated.The results show that the initial irregular shaped,randomly distributed L12 and DO22 phases are gradually transformed into cuboidal shape with round corner,regularly aligned along directions[100]and[001],and highly preferential selected microstructure is formed during the later stage of precipitation.The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics,and there is no linear relationship between the cube of the average size of precipitates and the aging time,which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner.The coarsening processes of L12 and DO22 phases are retarded in elastically constrained system.In the concurrent system of L12 and DO22 phases,there are two types of coarsening modes:the migration of antiphase domain boundaries and the interphase Ostwald ripening.
基金supported by the National Natural Science Foundation of China(No.50671084)the Doctoral Foundation of Northwestern Polytechnical University(No.CX200507).
文摘The interrupted aging mechanisms were applied to Ni75Al2.9V22.1 alloy by using the microscopic phase-field simulation method. For the single phase region existing at high temperature, the low content alloy was used as the study object. With the progressive aging mechanisms, the metastable phase γ′ of high temperature can be obtained from the low temperature two phase regions, and the quantity of γ′ phase reduces with increasing temperature. The θ single phase morphology at high temperature regions will turn to be the γ′＋θ two phase morphology at low temperature with the interrupted aging method. Despite of the different precipitation paths of γ′ phase, the precipitation mechanisms are the same for the low temperature aging and high temperature interrupted aging.
基金Funded by the National Natural Science Foundation of China (Nos.50941020, 10902086, 50875217, and 20903075)Natural Science Foundation of Shaanxi Province (Nos. SJ08-ZT05 and SJ08-B14)Doctorate Foundation of Northwest Polytechnical University (No. CX200905)
文摘Based on the microscopic phase-field model, the structure and migration characteristic of ordered domain interfaces formed between DO22 and L12 phase are investigated, and the atomistic mechanism of phase transformation from L12 （Ni3Al） to DO22 （Ni3V） in Ni75AlxV25-x alloys are explored, using the simulated microstructure evolution pictures and the occupation probability evolution of alloy elements at the interface. The results show that five kinds of heterointerfaces are formed between DO22 and L12 phase and four of them can migrate during the phase transformation from L12 to DO22 except the interface （002）D//（001）L. The structure of interface （100）D//（200）L and interface （100）D//（200）L·^1/2[001] remain the same before and after migration, while the interface （002）D//（002）L is formed after the migration of interface （002）D//（002）L·^1/2[100] and vice versa. These two kinds of interface appear alternatively. The jump and substitute of atoms selects the optimization way to induce the migration of interface during the phase transformation, and the number of atoms needing to jump during the migration is the least among all of the possible atom jump modes.
