The relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90° XY-scan, and 67° Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the near-surface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuß model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kröner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys.

中文翻译：

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LPBF IN718 微观结构与残余应力的相互作用

已经在用三种不同扫描策略（单向 Y 扫描、90° XY 扫描和 67° 旋转扫描）生产的试样上研究了与激光粉末床融合 (LPBF) IN718 合金相关的残余应力和微观结构之间的关系。同步加速器 X 射线能量色散衍射 (EDXRD) 结合光学轮廓测定法用于研究残余应力 (RS) 分布和从基板上取下试样时的变形。使用扫描电子显微镜 (SEM) 和电子背散射衍射 (EBSD) 进行体块和近表面区域的微观结构表征。在试样的顶面，在 Y 扫描试样中观察到最高的 RS 值，在 Rot 扫描试样中观察到最低，而在侧表面上趋势相反。从基板上取下试样后，大量 RS 仍保留在试样中，尤其是在 Y 和 Z 方向（分别为短试样尺寸和构建方向 (BD)）。在基板减薄和随后移除后在顶面上测量的变形主要归因于在构建方向上释放的 RS 量。重要的是，据观察，增材制造微结构挑战使用经典理论模型来计算基于衍射的 RS 分析所需的衍射弹性常数 (DEC)。发现当 Reuß 模型用于计算不同晶面的 RS 时，与传统使用的 Kröner 模型相反，结果表现出较低的散射。