镍基高温合金中温变形动态析出前期相和反位缺陷的协同演变历程.

The coupling macro/micro/nano stress are arose from nickel based superalloy by warm deformation, which will induce dynamic pre-precipitation and antisite defects. The antisite defects will cause non-coulomb force, conduction band minimum splitting, forbidden band trap, degeneracy lift, local distortion, local coordination environment variation, original symmetry space group deviation, interface Fermi level pinning effect. The cooperative evolution history between dynamic pre-precipitation and antisite defects is significant for the superalloy’s microstructures and performances..This project takes the nickel based superalloy that strengthened by both short and long-period ordered precipitations as research subject, the study consists of plastic deformation, precipitation strengthening, phase structures, point defects, and microscopic phase field computation. Based on the preparation and application background of short and long-period ordered precipitation strengthening nickel based superalloy, we summarize a scientific question of” cooperative evolution history between dynamic pre-precipitation and antisite defects”. We explore the thermodynamics stability, elastic soft direction, and transformation mechanism, and further discuss the localization transformation induced by local stress, cooperative evolution history of pre-precipitation and antisite defects, local coordination environment for individual sublattice, site preference of antisite defects. Ordering parameter, correlation function, structure function, coarsening dynamics index, scaling function are employed to quantitative characterization. The study provide theoretical supports for warm deformation-aging process integrated design and microstructure-performace optimization.

镍基高温合金中温变形时，宏/微/纳观应力耦合诱导动态析出前期相和反位缺陷，反位缺陷造成非库仑势能，导带底能级分裂，禁带局部能级陷阱，简并解除，局部畸变，局域配位环境变化，偏离原对称空间群，界面费米能级钉扎效应，前期相和反位缺陷的协同演变历程对显微结构、性能有重大影响。.本基金以短/长周期结构相强化镍基高温合金为对象，塑性加工、析出强化、相结构、点缺陷、微观相场模拟的研究相结合，源于短/长周期结构相强化镍基高温合金制备工艺的应用基础研究背景，凝练出“中温变形动态析出前期相和反位缺陷的协同演变历程”的科学命题。从热力学稳定性、弹性软方向、转变机制三个方面开展探索，深入到局域应力诱导局域相变、前期相和反位缺陷的协同演变早期、亚晶格局域配位环境、反位缺陷亚晶格选择，以序参数、关联函数、结构函数、粗化动力学指数、标度函数定量表征，为中温变形与时效工艺一体化设计，优化显微结构和性能，提供理论支撑。

镍基、铁镍基中高温合金，在高温、高压、高辐照等极端环境下服役，热/力/辐照等耦合效应影响组织和性能，微观组织及缺陷的协同演化将共同决定组织稳定性和性能稳定性，从而决定了设施服役安全性。采用介观尺度的相场方法模拟组织演化、有序畴界演化和微观缺陷演化，取得的重要结果如下。. (1) 阐明了前期相、沉淀相沉淀机制、析出序列及对应的成分、应力、温度等参数条件。前期相可以是L10、L10(M=1)、D022或L12，其中前期相的类型对成分最为敏感。前期相结构转变过程的原子重排涉及到反位缺陷的择优占位、取向扩散等，反位缺陷显示出局域配位差异决定的择优倾向；耦合应力大小和方向影响前期相的类型及其稳定沉淀相的取向，析出相引起的微观弹性应力和外加应力叠加导致反位缺陷扩散需要松弛应力作用，引起取向扩散和取向粗化组织。. (2) 研究B2-FeAl有序相的沉淀机制、有序畴演化和反位缺陷。B2-FeAl以等成分有序化机制析出；有序畴尺寸与时间呈线性关系，单轴压缩应变阻碍有序相长大，有序畴湮灭延缓, 大应力下反相畴界演化与轴向压缩应变轴垂直。温度越高，反位加剧；应变能增加，反位加剧； . (3) 相场方程耦合经典的缺陷反应速率理论，且引入温度场、辐照剂量、各向异性和温度梯度等实际服役环境特征，用于描述空位团簇或间隙团簇从形核到长大、粗化的形貌、尺寸和分布。阐明了辐照空洞的反常粗化现象、温度场效应、温度梯度、弹性不均匀应力场下辐照缺陷的簇聚和长大行为。以单组元、二组元、多个三组元合金为例，筛选出了与实验结果一致的合金组分。. 该工作为镍基、铁镍基合金从成分→工艺→组织调控→性能调控设计提供理论依据，启发新材料开发、新工艺设计，对于推动航空工业、核工业数据库建设、高通量计算、一体化设计、多尺度模拟方面具有重要意义。