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Phase Field Simulation of Dendritic Growth of Ternary Alloy with Multiple Grains

Author: WeiTao
Tutor: YangXiangJie
School: Nanchang University
Course: Materials Processing Engineering
Keywords: phase-field method dendrite growth numerical simulation ternary alloy multi-grain competitive growth
CLC: O781
Type: Master's thesis
Year: 2013
Downloads: 63
Quote: 0
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The phase-field method as a practical and effective method of simulation of solidification microstructure, able to simulate the changes of dendrite growth morphology in solidification without track the solid-liquid interface, and can simulate the solidification microstructure formation to predict the mechanical properties of the metal and optimize the production process parameters to achieve the ultimate aim to improve the quality of castings, and have a very long-term significance of the actual production.Established a simulation multi-grain growth of the ternary alloy phase-field model based on the improved KKS model in this paper, and use this model to solidification of Al-Cu-Mg ternary alloy microstructure evolution, Simulation of a single grain and multi-grain growth of dendrite growth. Undercooling, disturbance intensity, anisotropy, the third element, and latent heat affect Al-Cu-Mg alloy dendrite growth was studied.Simulated ternary alloy dendrite growth in non-isothermal conditions, observed dendrite lateral branch competitive growth and necking. In multi-grain initial stage of growth, there is no interaction between the various grains, and each grain independent growth, growth after a period of time, there is interaction between the dendrite, the phenomenon of the growth of competition, no longer meets the Ivantsov theory. Preferential growth direction of dendrite growth is more obvious in the case of anisotropic strength gradually increases, and dendritic morphology from the algae form gradually shift to the dendrite morphology, with increasing disturbance intensity, the dendrites lateral branches become more developed, the addition of1%of the disturbance will be able to get a better dendritic morphology. Study undercooling affect the Al-Cu-Mg ternary alloy single grain and multi-grain solidification of dendrite growth in non-isothermal conditions, the dendrites growth speed increases with increasing undercooling, the tip radius of curvature is getting smaller and smaller, lateral branch become more and more developed, dendrite trunk is getting smaller. With dendrite growth faster, making the dendrite solute segregation more serious, solute concentration gradient. Calculation regions elevated temperature increases with the undercooling increases, the corresponding temperature difference also increases, but the variation of the temperature is the same. As third crew solute Mg content reduce dendrite growth velocity gradually increases, the more developed lateral branch of the dendrite, the more serious the solute segregation, the maximum temperature is increasing. Contrast isothermal solidification and non-isothermal solidification simulation results in the case of multi-grain growth, in both cases can get a good dendritic morphology, but in isothermal solidification dendrite lateral branches more developed than non-isothermal solidification, the solidification rate is relatively large, this is caused by the latent heat in solidification, non-isothermal solidification closer to the actual solidification.

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CLC: > Mathematical sciences and chemical > Crystallography > Crystal growth > Theories of crystal growth
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