论文部分内容阅读
采用宏微观耦合方法对铝合金枝晶生长形貌进行模拟计算。由于对整个试样进行微观计算存在困难 ,所以采取的方案是整体计算温度场 ,而微观组织计算则是在试样中心区域选取其中一个单元进行 ,该单元的微观组织模拟被简化为二维计算。采用较大的网格和时间步长Δt计算宏观温度场 ,当选取的单元温度降到液相线以下时 ,在一个宏观时间步长Δt内 ,采用小网格和小时间步长δt对该单元进行微观组织计算 ,宏观、微观计算交替进行。形核过程采用了高斯分布模型 ,生长过程由相场方程来控制。微观区域内的初始温度分布由周围的宏观单元温度插值得到 ,界面过冷包含热过冷、成分过冷和曲率过冷。溶质分布则用混合溶质守恒方程来描述。为了描述二次枝晶的产生 ,在相场模型中引入了噪声。模拟结果与实际浇注的试样的金相结果以及其他学者的结果进行了比较。
The macro-micro coupling method was used to simulate the growth morphology of aluminum alloy dendrites. Because of the difficulty of microscopic calculation of the whole sample, the solution is to calculate the temperature field as a whole, and the microstructure calculation is performed by selecting one of the units in the center of the sample. The microstructure simulation of the unit is simplified to a two-dimensional calculation . The larger grid and the time step Δt are used to calculate the macro temperature field. When the temperature of the selected cell falls below the liquidus, a small grid and a small time step δt are used in a macroscopic time step Δt Unit microstructure calculation, macro, micro calculations alternately. The nucleation process uses Gaussian distribution model, the growth process is controlled by the phase field equation. The initial temperature distribution in the microscopic area is obtained by the interpolation of the surrounding macrocells. The supercooling of the interface includes the hot and cold components, the component subcooling and the curvature subcooling. Solute distribution is described by the mixed solute conservation equation. To describe the generation of secondary dendrites, noise was introduced into the phase field model. The simulation results are compared with the metallographic results of the actual cast samples and the results of other scholars.