镍基单晶高温合金再结晶过程模拟研究

NUMERICAL SIMULATION OF RECRYSTALLIZATION PROCESS OF NICKEL BASE SINGLE CRYSTAL SUPERALLOY

结合单晶高温合金各向异性的特点,建立了基于应力应变和变形储存能的物理数学模型,考虑了再结晶晶界迁移引起的晶粒长大过程.针对单晶高温合金变形过程进行应力应变模拟,考虑了不均匀变形对再结晶的影响,计算储存能分布,建立了再结晶临界储存能模型,模拟了镍基单晶高温合金在局部变形后热处理过程发生的静态再结晶过程.对DD6单晶高温合金试样表面进行冷变形处理,分别置于1280℃温度下进行不同时间的热处理,样品冷变形区域表面发生了不同程度的再结晶,并且随着时间延长,再结晶区域和晶粒尺寸逐渐增加.通过2D数值模拟方法研究这一过程,并将再结晶组织模拟结果与EBSD实验结果进行对比,结果吻合较好,表明借助于该模型能较好地模拟单晶高温合金的再结晶过程.

The formation of recrystallization can cause great damage on the performance of nickel base single crystal superalloy turbine blade. The stress, strain and stored energy distribution of single crystal superalloy were modeled and simulated under the condition of inhomogeneous deformation. The critical stored energy was established which takes the anisotropic mechanical properties of single crystal superalloy and the recrystallization grain boundary migration process into account. Based on the calculation of the critical stored energy, the recrystallization microstructure in the local deformation zone after heat treatment was simulated by using cellular automaton （CA） method. DD6 single crystal test bars were treated by the cold deformation process and then annealed at the temperature of 1280 ℃ for 30, 60 and 240 min. The experimental results showed that the recrystallization occurred on the surface near the deformation area. The recrystallization area and the grain size increased gradually with time. The simulated microstructure results agree well with the experimental ones （EBSD） and indicate that the recrystallization process of single crystal superalloy can be well simulated by the proposed model.