Ta含量对铸造高温合金DZ411长期热暴露过程中γ′相粗化的影响

Effect of Ta Content on γ’ Phase Coarsening During Long-Term Thermal Exposure of DZ411 Cast Superalloys

借鉴材料基因工程中高通量实验的做法,采用快速凝固技术和定向凝固技术制备含Ta浓度梯度的定向合金,并在900℃进行长期热暴露实验,研究不同Ta浓度对铸造高温合金热暴露中γ′相生长速率的影响。通过对不同热暴露时间γ′相尺寸变化的统计,结合粒子粗化理论计算发现,随着Ta浓度增加,粗化速率常数一直在减小。通过合金中有效扩散系数计算发现,热暴露前期,高Ta浓度处的γ′相形成元素平均扩散系数较低,使得γ′相生长速率放缓。在长期热暴露后期,高Ta浓度处γ′相生长速率依旧缓慢,并且γ相基体间产生了大量位错,经测量,两相的相界面间的晶格错配度减小,阻碍了相形成元素向γ′相内迁移,导致γ′相生长速率减缓。

Based on the practice of high-through put experiment in material genetic engineering, directional alloys containing Ta concentration gradient were prepared by LMC and HRS directional solidification method. Long term heat exposure experiments were carried out at 900 ℃ to study the effects of different Ta concentrations on the growth rate of the γ′ phase in the alloys. First, the change of size of the γ′ phase was statistically analyzed, and then through the theoretical calculation of particle coarsening, it is found that the coarsening rate constant decreased with the increase of the Ta concentration. Through the calculation of effective diffusion coefficient in the alloy, it is found that at the high Ta concentration in the early stage of the heat exposure, the average diffusion coefficient of the γ′ phase forming elements was low, which made the growth rate of the γ′phase slows down. In the late stage of the long-term heat exposure, at high Ta concentration, the growth rate of the γ′ phase was still slow, and a large number of dislocations were generated between the γ phase matrix.After measurement, the lattice mismatch between the γ/γ′ phase interfaces of the two phases decreases, which hinders the orientation of γ′ phase forming elements in γ′ phase migration, and γ′ phase growth rate becomes slow.