Hastelloy C276高温合金热加工微观组织演化元胞自动机模拟

采用Gleeble热模拟试验机对Ni-Cr-Mo系高温合金Hastelloy C276进行单道次和双道次热压缩试验,获得了不同热变形条件下的流变应力曲线和微观组织,在此基础上回归了该合金热变形物理冶金模型及参数,进而构建了微观组织拓扑演化的元胞自动机模型。结果表明:Hastelloy C276高温合金在高温热压缩过程中易发生动态再结晶,当动态再结晶不完全时,在热压缩保温或道次间歇内,再结晶晶粒将进一步快速生长而发生亚动态再结晶。Hastelloy C276高温合金再结晶行为对变形温度、变形速率、应变量等工艺参数敏感;构建的元胞自动机模型,集成计算了热压缩和道次间歇过程中的位错密度、再结晶形核及晶界迁移等,可有效表征多工艺参数下Hastelloy C276高温合金热压缩过程中的微观组织拓扑结构演化和应力-应变响应。

Cellular automaton simulation of microstructure evolution of Hastelloy C276 superalloy during hot processing

Single-pass and double-pass hot compression tests for Ni-Cr-Mo-based superalloy Hastelloy C276 were conducted by Gleeble thermal-mechanical simulator, and the flow stress curves and microstructure under different hot deformation conditions were obtained. On this basis, the physical metallurgy models as well as the parameters were determined, and then the cellular automaton model was established for topological evolution of microstructure. The results show that the dynamic recrystallization is prone to occur of the Hastelloy C276 superalloy during high temperature compression. When the dynamic recrystallization is not complete, the recrystallized grains will further grow rapidly during the heat preservation or the hot compression pass intermittence, so that metadynamic recrystallization will occur. The recrystallization behavior of the Hastelloy C276 superalloy is sensitive to the hot processing parameters, including the deformation temperature, strain rate, strain and so on. The dislocation density evolution, recrystallization nucleation, and migration of grain boundary, etc during the heat preservation and the hot compression pass intermittence can be calculated simultaneously by the constructed cellular automaton model, which can be used to predict both the microstructure topological structure evolution and the stress-strain response of the Hastelloy C276 superalloy during high temperature compression effectively.