Ti-45at.%Al合金定向凝固过程中显微组织演化的计算机模拟

Numerical simulation of microstructure evolution during directional solidification of Ti-45at.%Al alloy

采用基于溶质扩散控制模型CA方法对Ti-45at.%Al合金定向凝固过程中显微组织演化过程进行了数值模拟.模拟结果表明,在温度梯度较高时,初生晶核间距无论大小,均可通过分枝或竞争生长而使一次胞晶/枝晶间距得到调整.在抽拉速度一定情况下,随着温度梯度增加,胞晶/枝晶间距减小,在温度梯度一定情况下,随着抽拉速度增大,观察到胞晶/枝晶混合结构,混合结构区随温度梯增大而增大,模拟结果与实验观察相符合.

The microstructural evolution of Ti-45at. % Al alloy during directional solidification was simulated by applying a solute diffusion controlled solidification model, and the results have showed that under high thermal gradient the stable primary spacing can be adjusted by branching or competitive growth, irrelevant of the initial seed spacing. In addition, under a given pulling speed, increasing thermal gradient decreases primary cell/dendrite spacing, and under a given thermal gradient, increasing pulling velocity, we have observed a cell/dendrite transition region consisting of cells and dendrites, and which varies with the thermal gradient in a contradicting way, i.e. increasing the thermal gradient leading to the decrease of the range of the transition region. The simulated results agree reasonably well with experiment results.