In this work, quantitative crystallographic and microstructural analyses of γ, γ′, γ’‘, δ, and MC carbide phases are performed on wrought samples, samples fabricated via additive manufacturing (AM), and samples that underwent hot isostatic pressing (HIP) after AM of alloy Inconel 718 (IN718). In doing so, an advanced neutron diffraction-based procedure is developed facilitating the determination of volume fractions of every detectable phase in the alloy. To supplement the diffraction procedure, precipitate sizes are measured by scanning electron microscopy. Moreover, semi-quantitative elemental analyses are performed by energy dispersive spectroscopy. Finally, image thresholding is carried out on micrographs of samples that underwent cathodic dissolution to create secondary electron contrast between phases to verify the phase fractions determined from the neutron diffraction datasets. The study reveals a significantly higher volume fraction of δ phase and a significantly lower volume fraction of γ’’ phase governing a higher strength of the AM material relative to the lower strength AM + HIP and wrought materials. Furthermore, γ’ and MC volume fractions are found similar in the materials despite the differences in MC morphology, elemental composition and distribution controlling the dispersion strengthening. These results are presented and discussed in this paper along with the procedure developed for determining volume fractions of all detectable phases present in the alloy.

在这项工作中，对锻造样品，通过增材制造（AM）制造的样品以及经过热等静压（HIP）的样品进行了γ，γ'，γ''，δ和MC碳化物相的定量晶体学和显微组织分析在合金Inconel 718（IN718）的AM之后。为此，开发了一种先进的基于中子衍射的方法，有助于确定合金中每个可检测相的体积分数。为了补充衍射程序，通过扫描电子显微镜测量沉淀物的大小。此外，通过能量色散光谱进行半定量元素分析。最后，在经过阴极溶解以在各相之间产生二次电子对比度的样品显微照片上执行图像阈值处理，以验证从中子衍射数据集确定的相分数。研究表明，相对于较低强度的AM + HIP和锻造材料，δ相的体积分数明显较高，而γ''相的体积分数则明显较低，这决定了AM材料的强度更高。此外，尽管MC形态，元素组成和分布控制分散增强，但在材料中发现γ'和MC的体积分数相似。本文将介绍和讨论这些结果，以及为确定合金中所有可检测相的体积分数而开发的程序。