1种新的模拟铝合金铸态组织的随机性方法

采用1种新的随机性模拟方法并与宏观传热过程相耦合，对铝合金的微观组织进行了模拟研究。计算中采用了简化的枝晶形状。建立了简化的枝晶形状的物理与数学模型，并提出了1种形状函数来描述晶粒的外部轮廓。基于简化的晶粒形状，采用坐标变换技术来描述过冷液相中晶粒的生长过程及其对周围节点的捕获过程。连续形核模型被用来处理异质形核现象，在生长模型中则考虑了枝晶尖端生长动力学和择优生长方向。开发了等轴晶生长的模拟程序，并进行了二维计算。进行了浇注金属型和砂型试样的模拟验证实验。结果表明，对两种不同的工艺，所得到的晶粒组织不同，金属型铸造时得到的晶粒尺寸较小，砂型铸造的较大。模拟结果与金相观察结果相符。

A New Stochastic Modeling Method for the Microstructure of Aluminum Alloy

Microstructure modeling of aluminum alloy castings has been carried out by using a new stochastic modeling methods coupled with macro heat transfer calculations. The actual dendritic shape is substituted for the square envelope in the cellular automaton model. A physical model and a mathematical model for the simplified dendrite shape are established in the paper, in which a shape function is presented to describe the dendrite shape contour. On the basis of the simplified grain shape, a coordinate transformation method is used to describe the equiaxed grain growth in the undercooled melts and the node capturing during the further growth of a grain. A continuous nucleation model is applied to deal with heterogeneous nucleation phenomenona. Dendrite tip growth kinetics and preferential <100> crystallographic orientation are taken into account. The stochastic nature of nucleation process as well as the deterministic of dendrite growth is considered to simulate the crystal growth. A microstructure simulation scheme is developed to model the grain formation according to the above model. Two- dimensional calculations are performed to simulate the evolution of equiaxed dendritic morphologies. In order to verify the modeling results, sample castings are cast in sand molds and metal molds. Simulation results show that grain size is smaller for metal mold casting, but larger for sand mold casting, in good agreement with both the experimental results and the postulated solidification mechanism.