ZL201铝合金副车架凝固过程的微观组织模拟

Microstructure simulation of ZL201 aluminum alloy auxiliary frame in solidification process

摘要:

采用元胞自动化(CA)方法对ZL201铝合金副车架的凝固过程和显微组织进行了模拟，建立了温度场和组织模拟场（CAFE）。对于面、体网格的划分，根据ZL201铝合的固相线和液相线分别确定了六种不同的形核面。温度场的凝固过程模拟结果表明通过油冷可以很好地控制形核率和生长速率在最合适的范围内，形核率为1/276 s·cm3，生长速率为65.2μm/s。通过热力学相图的计算结果表明Al3Ti相的形成过程，它从周围的铝原子中吸收共价电子。随着钛含量的增加，Al3Ti的析出温度升高。此外，Al3Ti的含量也从0.144mol%提高到0.698mol%，晶粒细化的效果也随之越来越明显。通过对ZL201铝合金副车架的微观组织、对应的<100>取向极图和金相组织的模拟和实验对照，表明Ti含量的变化对ZL201铝合金副车架的微观组织的晶粒细化效果有显著影响。随着钛含量的增加，新相Al3Ti促进了晶粒细化和组成的均匀性。从模拟的<100>极图可知，Ti含量的增加有利于晶粒的择优取向，而且晶粒细化的方式是通过减缓晶粒之间的生长竞争性来实现的。模拟的结果与实验得到的金相组织基本一致。

Abstract:

The solidification process and microstructure of ZL201 aluminum alloy auxiliary frame were simulated by Cellular Automation(CA) method, and the temperature field and CAFE(microstructure simulation) field were established. According to the solid and liquid phase lines of ZL201 aluminum alloy, the six different nucleating surfaces were determined. The simulation results of temperature field show that the nucleation rate and growth rate can be controlled in the most suitable range by oil cooling. The nucleation rate is 1/276 s·cm3and growth rate is 65.2μm/s. The calculation results of thermodynamic phase diagram show that in the formation process of Al3Ti phase, which absorbs covalent electrons from surrounding aluminum atoms. With the increasing of titanium content, the precipitation temperature of Al3Ti increases. In addition, the content of Al3Ti has increased from 0.144mol% to 0.698mol%, and the effect of grain refinement became more and more obvious. Through the simulation of the microstructure of ZL201 aluminum alloy auxiliary frame, the corresponding <100> polar diagram and the experimental metallographic structure, it is shown that the change of Ti content has a significant impact on the grain refinement effect of ZL201 aluminum alloy auxiliary frame microstructure. With the increasing of titanium content, the new phase Al3Ti promotes grain refinement and composition uniformity. It can be seen from the simulated polar diagram of <100> that the increase of Ti content is conducive to the preferential orientation of grains, and the grain refinement is achieved by slowing down the competition among grains. The results of simulation are basically consistent with the metallographic structure obtained by experiment.