Abstract The effect of the annealing temperature of a Ti-50.9 at.% Ni nanocrystalline alloy with an inhomogeneous grain/subgrain structure on Ti3Ni4 precipitation was investigated. The evolution of sizes, morphology, and spatial distribution of Ti3Ni4 particles after annealing at 300 °C, 400 °C and 500 °C studied. Found that Ti3Ni4 particles nucleate by a heterogeneous mechanism predominantly in the substructure and almost not observed in nanograins. With an increase in the temperature of annealing the Ti3Ni4 particles increase in size and their spatial distribution changes from location in subgrains at dislocations (at 300 °C) to precipitation at subboundaries (at 400 °C). The features of recovery and recrystallization in the grain/subgrain structure at 500 °C identified and their relationship with the processes of dissolution and coagulation of Ti3Ni4 particles revealed. The large-scale microstructural heterogeneity leading to different precipitation behavior between substructure regions and nanograins groups is considered as an additional cause of the multi-stage martensite transformation sequence B2 ↔ R ↔ B19′.

中文翻译：

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富镍钛镍合金热处理晶粒/亚晶粒纳米结构中的 Ti3Ni4 析出特征

摘要 研究了具有不均匀晶粒/亚晶粒结构的 Ti-50.9 at.% Ni 纳米晶合金的退火温度对 Ti3Ni4 析出的影响。研究了在 300 °C、400 °C 和 500 °C 下退火后 Ti3Ni4 颗粒的尺寸、形态和空间分布的演变。发现 Ti3Ni4 颗粒主要在亚结构中通过异质机制成核，而在纳米颗粒中几乎没有观察到。随着退火温度的升高，Ti3Ni4 颗粒的尺寸增加，它们的空间分布从位错（300°C）的亚晶粒位置变化到亚边界沉淀（400°C）。确定了 500 °C 下晶粒/亚晶粒结构的恢复和再结晶特征，并揭示了它们与 Ti3Ni4 颗粒溶解和凝聚过程的关系。导致亚结构区域和纳米晶粒组之间不同沉淀行为的大规模微观结构不均匀性被认为是多阶段马氏体转变序列 B2 ↔ R ↔ B19' 的另一个原因。