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Spinodal decomposition versus classical γ′ nucleation in a nickel-base superalloy powder: An in-situ neutron diffraction and atomic-scale analysis
Acta Materialia ( IF 9.4 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.actamat.2020.09.055
David M. Collins , Neil D’Souza , Chinnapat Panwisawas , Chrysanthi Papadaki , Geoff D. West , Aleksander Kostka , Paraskevas Kontis

Abstract Contemporary powder-based polycrystalline nickel-base superalloys inherit microstructures and properties that are heavily determined by their thermo-mechanical treatments during processing. Here, the influence of a thermal exposure to an alloy powder is studied to elucidate the controlling formation mechanisms of the strengthening precipitates using a combination of atom probe tomography and in-situ neutron diffraction. The initial powder comprised a single-phase supersaturated γ only; from this, the evolution of γ′ volume fraction and lattice misfit was assessed. The initial powder notably possessed elemental segregation of Cr and Co and elemental repulsion between Ni, Al and Ti with Cr; here proposed to be a precursor for subsequent γ to γ′ phase transformations. Subsolvus heat treatments yielded a unimodal γ′ distribution, formed during heating, with evidence supporting its formation to be via spinodal decomposition. A supersolvus heat treatment led to the formation of this same γ′ population during heating, but dissolves as the temperature increases further. The γ′ then reprecipitates as a multimodal population during cooling, here forming by classical nucleation and growth. Atom probe characterisation provided intriguing precipitate characteristics, including clear differences in chemistry and microstructure, depending on whether the γ′ formed during heating or cooling.

中文翻译:

镍基高温合金粉末中的旋节线分解与经典 γ' 成核:原位中子衍射和原子尺度分析

摘要 当代粉末基多晶镍基高温合金的显微组织和性能在很大程度上取决于加工过程中的热机械处理。在这里,使用原子探针断层扫描和原位中子衍射的组合研究了合金粉末受热的影响,以阐明强化析出物的控制形成机制。初始粉末仅包含单相过饱和 γ;由此,评估了 γ' 体积分数和晶格失配的演变。初始粉末显着具有Cr和Co的元素偏析以及Ni、Al和Ti与Cr之间的元素排斥;此处提议作为后续 γ 到 γ' 相变的前体。Subsolvus 热处理产生单峰γ'分布,在加热过程中形成,有证据支持它是通过旋节线分解形成的。超溶线热处理导致在加热过程中形成相同的 γ' 群,但随着温度的进一步升高而溶解。γ'然后在冷却过程中作为多峰群再沉淀,这里是通过经典的成核和生长形成的。原子探针表征提供了有趣的沉淀特征,包括化学和微观结构的明显差异,这取决于 γ' 是在加热还是冷却过程中形成的。这里通过经典的成核和生长形成。原子探针表征提供了有趣的沉淀特征,包括化学和微观结构的明显差异,这取决于 γ' 是在加热还是冷却过程中形成的。这里通过经典的成核和生长形成。原子探针表征提供了有趣的沉淀特征,包括化学和微观结构的明显差异,这取决于 γ' 是在加热还是冷却过程中形成的。
更新日期:2020-11-01
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