Abstract The thin plate is a promising light-weight structure to broaden applications of Inconel 718 superalloy in aerospace and transportation industries. In the present work, selective laser melting (SLM) technology was applied to manufacture a series of Inconel 718 thin walls (ultra-thin plates) to explore their printability, microstructures, crystallographic features and microhardness under keyhole and conduction modes. Results show that it is feasible to manufacture Inconel 718 thin walls with a thickness of ~0.2 mm by SLM. Keyhole mode is favorable for a better printability, finer dendrites, the precipitation of strengthening phases of γ′/γ″, a stronger 〈001〉 texture intensity and a higher microhardness in the center zone of the SLMed thin wall. Conduction mode contributes to the uniform microstructures and microhardness in the marginal and center zones of the thin wall. Also, the decrease of area fraction in strengthening phases and the increase of Laves phase result in a decreasing trend of microhardness along the deposition direction. Finally, microstructural formation and evolution mechanisms of SLMed thin walls under two modes are proposed based on the solidification conditions and vertical thermal cycles.

中文翻译：

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选择性激光熔化 Inconel 718 薄壁的可印刷性、微观结构、晶体学特征和显微硬度

摘要 薄板是一种有前景的轻质结构，可拓宽Inconel 718高温合金在航空航天和交通运输行业的应用。在目前的工作中，选择性激光熔化 (SLM) 技术被应用于制造一系列 Inconel 718 薄壁（超薄板），以探索其在键孔和传导模式下的可印刷性、微观结构、晶体学特征和显微硬度。结果表明，通过 SLM 制造厚度约为 0.2 mm 的 Inconel 718 薄壁是可行的。Keyhole 模式有利于更好的印刷适性、更细的枝晶、γ'/γ'' 强化相的沉淀、更强的 <001> 织构强度和 SLMed 薄壁中心区更高的显微硬度。传导模式有助于薄壁边缘和中心区域的均匀微观结构和显微硬度。此外，强化相中面积分数的减少和Laves相的增加导致显微硬度沿沉积方向呈下降趋势。最后，基于凝固条件和垂直热循环，提出了两种模式下SLMed薄壁的微观结构形成和演化机制。