Al—Cu合金凝固冷却曲线及晶粒组织特征的计算机模拟

利用宏观－微观耦合的模型和热焓法处理结晶潜热，用外节点直接差分法数值计算技术，模拟了Ａｌ－２ｗｔ％Ｃｕ合金凝固过程的冷却曲线和晶粒组织特征，并与实验结果进行了比较。结果表明：冷却速率越大的凝固区域，再辉出现得越早，平台凝固段越短。模拟所得冷却曲线和晶粒组织特征同实测值吻合较好。

Computer Simulation of the Cooling Curves and Grain Structure in Solidification of Al 2wt%Cu Alloy

It is well known that macroscopic models were often used to simulate the cooling curves in solidification. However, they could not predict the characteristics of grain structure because the microscopic mechanisms involved in the solidification process were not taken into account. We used a macro microscopic model to investigate the cooling curves and grain structure in solidification. At the macroscopic level, the heat diffusion equation was solved with an enthalpy formulation using a DFDM(direct finite difference method) explicit scheme. Instead of using, as had been usually done, a unique relationship between temperature and enthalpy, the specific heat and latent heat contributions, whose sum equals the variation of enthalpy, were calculated using a microscopic model of solidification. The microscopic model takes into account the nucleation of new grains in the undercooled melt and the kinetics of the dendrite. We found that the simulated cooling curves which exhibit recalescences and temperature plateaus, as well as the simulated average grain size, agree well with measured ones.