中文摘要：

分析了CAFE法模拟凝固过程微观组织的物理本质、数值计算方法,并应用CAFE法模拟了易切削钢9SMn28的三维微观组织,优化了9SMn28的成分。在CAFE模型中,形核密度用高斯分布来描述;枝晶尖端生长动力学用KGT模型进行计算;枝晶生长的择优取向是〈100〉方向,并可实现枝晶生长的竞争机制;FE与CA耦合是通过FE节点和CA元胞之间的插值实现的。易切削钢9SMn28微观组织模拟结果与实验吻合较好,确定的碳、磷、锰、硅、硫的最佳质量分数分别为0.15%、0.10%、1.2%、0.08%、0.36%,并对优化结果进行了模拟,有效地改善了9SMn28的凝固组织。

英文摘要：

The CAFE method simulated 3D-microstructure in solidification processes was analyzed. The CAFE method is the combination of cellular automaton （CA） model with finite element （FE） method which is a macromicro coupling model, and this method can simulate the competitive growth of columnar grains and equiaxed grains, the formation of columnar region, relationship between grain boundary orientation and hot grads, columnar-to equiaxed transition, and the shape of equiaxed grains in non isothermal temperature field, etc. The nucleation density is described by Gaussian distribution in the CAFE model. Calculation of kinetics of the dendrite tip growth is done according to the model of KGT. The crystallographic orientation 〈100〉 is selected preferentially, and the competition of crystal growth is developed directly. The coupling of FE and CA is realized through the interpolation between FE mesh and CA cells. Based on the CAFE method, 3D-microstructure of 9SMn28 free cutting steel was simulated in solidification processes, and the simulation results are consistent with those of experiment. The composition of 9SMn28 free cutting steel was optimized; the optimum C, P, Mn, Si and S contents are 0.15%, 0.10%, 1. 2%, 0.08% and 0.36%, respectively. The optimization results were also simulated and the solidifica- tion structure is improved obviously.