The solidification microstructure of Al-Si alloy was observed in the experiment,the second dendrite arm spacing(SDAS)was measured,and the effect of temperature on the microstructure was analyzed.Phase-field(PF)model i...The solidification microstructure of Al-Si alloy was observed in the experiment,the second dendrite arm spacing(SDAS)was measured,and the effect of temperature on the microstructure was analyzed.Phase-field(PF)model incorporating natural convection caused by gravity was employed to simulate the microstructure evolution of Al-Si alloy under the experimental conditions.Good agreements between the experimental and simulation results verified the reliability of the simulation approach proposed in this study.Based on the proposed model,a series of simulation cases(2D and 3D)were performed to investigate the evolution of columnar and equiaxed dendritic structures.It was found that the solute content of the alloy had little impact on the microstructure evolution,while the solute expansion coefficient had obvious effect on the dendrite tip velocities.Significant improvement of computational efficiency was achieved via novel algorithms,making it possible to perform massive simulation for studying the evolution of solidification microstructures,which is hard to be directly observed in experiments via synchrotron radiation for Al-Si alloy.展开更多
In this work, a cellular automaton model has been developed to simulate the microstructure evolution of U-Nb alloy during the solidification process. The preferential growth orientation, solute redistribution in both ...In this work, a cellular automaton model has been developed to simulate the microstructure evolution of U-Nb alloy during the solidification process. The preferential growth orientation, solute redistribution in both liquid and solid, solid/liquid interface solute conservation, interface curvature and the growth anisotropy were considered in the model. The model was applied to simulate the dendrite growth and Nb microsegregation behavior of U-5.5 Nb alloy during solidification, and the predicted results showed a reasonable agreement with the experimental results. The effects of cooling rates on the solidification microstructure and composition distribution of U-5.5 Nb were investigated by using the developed model. The results show that with the increase of the cooling rate, the average grain size decreases and the Nb microsegregation increases.展开更多
Although considerable research has focused on the relationship between ecosystem structure and function, interactions of plant morphological characteristics, species composition and richness with eco-hydrological func...Although considerable research has focused on the relationship between ecosystem structure and function, interactions of plant morphological characteristics, species composition and richness with eco-hydrological functions remain unclear. We measured water adherence （i.e. the capacity of a plant species to retain water）, documented plant surface morphology and observed surface runoff at three sites in China. The adhering water ratios for each plant species differed, ranging from 17.1% to 151.5% in leaves, and from 14.4% to 41.1% in branches. Small, light-weight, soft, non-cuticularized leaves that were densely situated on small branches showed good water adherence. The next best adherence was found by branches with intermediately coarse surfaces. The plant species with high standing biomass also showed good water adherence, and the contribution of a species to total adherence was dependent upon its aboveground standing biomass. Vegetation parameters strongly affected water adherence, whereas the effect of species richness was not significant. Conversely, species richness showed a significant influence on surface runoff. The effect of plant morphological characteristics and composition constitutes a basic process in the regulation of eco-hydrological function, and vegetation parameters play somewhat different roles in that regulation. The key roles must therefore be considered from a management perspective.展开更多
基金financial supports from the National Key R&D Program of China(No.2016YFB0701201)the Fostering Project in Innovation Funds of China Academy of Engineering Physics(No.PY2019078)financial support from China Scholarship Council。
文摘The solidification microstructure of Al-Si alloy was observed in the experiment,the second dendrite arm spacing(SDAS)was measured,and the effect of temperature on the microstructure was analyzed.Phase-field(PF)model incorporating natural convection caused by gravity was employed to simulate the microstructure evolution of Al-Si alloy under the experimental conditions.Good agreements between the experimental and simulation results verified the reliability of the simulation approach proposed in this study.Based on the proposed model,a series of simulation cases(2D and 3D)were performed to investigate the evolution of columnar and equiaxed dendritic structures.It was found that the solute content of the alloy had little impact on the microstructure evolution,while the solute expansion coefficient had obvious effect on the dendrite tip velocities.Significant improvement of computational efficiency was achieved via novel algorithms,making it possible to perform massive simulation for studying the evolution of solidification microstructures,which is hard to be directly observed in experiments via synchrotron radiation for Al-Si alloy.
基金supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics(Grant No.2015B0203031)the Science Challenge Program(Grant No.TZ20160040201)
文摘In this work, a cellular automaton model has been developed to simulate the microstructure evolution of U-Nb alloy during the solidification process. The preferential growth orientation, solute redistribution in both liquid and solid, solid/liquid interface solute conservation, interface curvature and the growth anisotropy were considered in the model. The model was applied to simulate the dendrite growth and Nb microsegregation behavior of U-5.5 Nb alloy during solidification, and the predicted results showed a reasonable agreement with the experimental results. The effects of cooling rates on the solidification microstructure and composition distribution of U-5.5 Nb were investigated by using the developed model. The results show that with the increase of the cooling rate, the average grain size decreases and the Nb microsegregation increases.
基金Project supported by the National Natural Science Foundation of China(Nos.41271484 and 41261079)the Fujian Provincial Natural Science Foundation of China(Nos.2013J01166 and 2012J05030)
基金supported by grants from the National Natural Science Foundation of China (40861015)the Foundation of State Key Laboratory of Soil Erosion and Dry-land Farming on the Loess Plateau (10501-208)the Natural ScienceFoundation of Yunnan Province, China (2000C0001P)
文摘Although considerable research has focused on the relationship between ecosystem structure and function, interactions of plant morphological characteristics, species composition and richness with eco-hydrological functions remain unclear. We measured water adherence （i.e. the capacity of a plant species to retain water）, documented plant surface morphology and observed surface runoff at three sites in China. The adhering water ratios for each plant species differed, ranging from 17.1% to 151.5% in leaves, and from 14.4% to 41.1% in branches. Small, light-weight, soft, non-cuticularized leaves that were densely situated on small branches showed good water adherence. The next best adherence was found by branches with intermediately coarse surfaces. The plant species with high standing biomass also showed good water adherence, and the contribution of a species to total adherence was dependent upon its aboveground standing biomass. Vegetation parameters strongly affected water adherence, whereas the effect of species richness was not significant. Conversely, species richness showed a significant influence on surface runoff. The effect of plant morphological characteristics and composition constitutes a basic process in the regulation of eco-hydrological function, and vegetation parameters play somewhat different roles in that regulation. The key roles must therefore be considered from a management perspective.
