匀变速抽拉对镍基单晶高温合金显微组织及晶体取向演化行为的影响

Effect of Uniformly Variable Withdrawal on Microstructure and Crystal Orientation Evolution of Ni-based Single Crystal Superalloy

定向凝固熔模铸造单晶叶片过程中凝固过程难以达到稳态。本文采用定向凝固实验结合数值模拟的方法,研究了匀变速抽拉条件(0~200μm/s和200~0μm/s)下镍基单晶高温合金非稳态凝固过程中的显微组织与晶体取向演化过程。结果表明:同一瞬时抽拉速率下匀加速抽拉样品的一次枝晶间距大于匀减速的情况。定向凝固过程中晶体取向偏差具有随机波动性,匀加速抽拉下的晶体取向波动幅度大于匀减速的情形。最后,结合数值模拟的温度场结果分析了凝固组织和晶体取向演化机制。

It is difficult to achieve a steady state during the solidification process in the directional solidification investment casting of single crystal blades.In this paper,a combination of directional solidification experiments and numerical simulations was employed to investigate the microstructure and crystal orientation evolution during the non-steady-state solidification process of nickel-based single crystal superalloys under uniformly variable withdrawal rate conditions(0~200μm/s and 200~0μm/s).The results indicated that the primary dendrite arm spacing of samples extracted at a uniformly accelerated rate was greater than that of samples extracted at a uniformly decelerated rate,when both were operating at the same instantaneous withdrawal rate.The crystal orientation deviation exhibited random fluctuations during the directional solidification process,with a larger fluctuation amplitude under uniformly accelerated withdrawal compared to that of uniformly decelerated withdrawal rate.Finally,the mechanisms of solidification microstructure and crystal orientation evolution were analyzed in conjunction with the temperature field results from numerical simulations.