Abstract The microstructure of single crystal superalloy with and without tin layer on the surface of as-cast and heat-treatment state was investigated by optical microscope (OM) and scanning electron microscopy (SEM). The composition of different regions on the surface was tested by energy dispersive X-ray (EDS). The reaction intermetallic compound (IMC) formed in the heat treatment process was confirmed by X-ray diffraction (XRD). The orientations of different microstructure in samples as heat treatment state were determined by electron back-scattering diffraction (EBSD) method. The porosity location in the interdendritic region was observed by X-ray computed tomography (XCT). The experiment results showed that the remained Sn on the surface of the superalloy reacted with Ni, and then formed Ni 3 Sn 4 in the as-cast state. Sn enriched by diffusion along the porosity located in the interdendritic region and γ + γ′ (contain a little of Sn) eutectic and Ni 3 Sn 2 formed in single crystal superalloy during heat treatment, and the recalescence behaviors were found. Ni 3 Sn 2 nucleated independently in the cooled liquid at the front of (γ + γ′) (Sn) eutectic. The nucleation and growth mechanism of the eutectic and Ni 3 Sn 2 IMC during heat treatment was discussed in the present paper.

中文翻译：

---

Ni-Sn共晶在单晶高温合金中的形核和生长机制

摘要 采用光学显微镜(OM)和扫描电子显微镜(SEM)研究了铸态和热处理状态表面有锡层和无锡层的单晶高温合金的显微组织。通过能量色散X射线（EDS）测试表面不同区域的组成。热处理过程中形成的反应金属间化合物（IMC）通过X射线衍射（XRD）得到证实。采用电子背散射衍射（EBSD）方法测定热处理状态下样品中不同显微组织的取向。通过 X 射线计算机断层扫描 (XCT) 观察树突间区域的孔隙位置。实验结果表明，高温合金表面残留的Sn与Ni反应，形成铸态Ni 3 Sn 4 。Sn沿枝晶区的孔隙扩散富集，热处理过程中在单晶高温合金中形成γ+γ′（含少量Sn）共晶和Ni 3 Sn 2 ，并发现其再辉行为。Ni 3 Sn 2 在(γ + γ') (Sn) 共晶前沿的冷却液中独立成核。本文讨论了共晶和Ni 3 Sn 2 IMC在热处理过程中的成核和生长机制。