Quantitative microstructural analysis was carried out to determine the size and volume fraction of strengthening phases: gamma double prime (γ″) and gamma prime (γ′); in additively manufactured (AM) Inconel 718 (IN718) with an emphasis on the utilization of Nb for γ″ formation during aging treatment. Powder bed fusion AM (PBF-AM) technique was used to generate coupons using indigenously synthesized IN718 alloy powder. Microstructural studies using transmission electron microscope (TEM) and small angle x-ray scattering (SAXS) were carried out on powder bed fusion-additive manufactured (PBF-AM) coupons in as-built condition (as processed) and in three different heat-treated conditions: solutionizing at three different temperatures (980, 1030 and 1080 °C) followed by double aging treatment. As-built microstructure consists of dendritic structure accompanied with Nb segregation along the interdendritic regions resulting in the formation of a Nb rich interdendritic phases dispersed within the interdendritic Nb-rich γ matrix. The inhomogeneous Nb distribution resulted in preferential precipitation of coarse δ during solutionization at 980 °C and further coarse γ″during direct aging and aging subsequent to solutionizing at 1030 °C. As-cast structure and related elemental segregation got modified during solutionization at 1080 °C and resulted homogeneous γ″ precipitation. Though the average size of γ″precipitates remained same in all aged samples, volume fraction increased with increasing solutionization temperature. SAXS studies were carried out on PBF-AM as well as conventionally produced wrought samples with the similar heat treatment conditions and confirmed that PBF-AM built IN718 aged samples solutionized at 1030 °C and 1080 °C resulted in γ″ precipitates with average precipitate size and volume fraction similar to that of the wrought-IN718 sample solutionized at 1080 °C.

进行了定量的微观结构分析，以确定强化相的大小和体积分数：γ双素（γ”）和γ素（γ'）；在增材制造（AM）Inconel 718（IN718）中进行了研究，重点是在时效处理过程中利用Nb形成γ''。粉末床融合AM（PBF-AM）技术用于使用本地合成的IN718合金粉末生成试样。在构建状态（加工状态）和三种不同的加热条件下，对粉末床熔融添加剂制造的（PBF-AM）试样进行了使用透射电子显微镜（TEM）和小角度X射线散射（SAXS）的微观结构研究。处理条件：在三种不同温度（980、1030和1080°C）下固溶，然后进行双重时效处理。竣工的微观结构由树枝状结构以及沿树枝状区域的Nb偏析引起，形成了分散在树枝状富Nbγ基质中的富Nb树枝状相。Nb分布不均匀导致在980°C固溶过程中优先析出粗δ，在直接时效和1030°C固溶后的老化过程中进一步产生粗γ''。在1080°C固溶过程中改变了铸态结构和相关元素的偏析，导致均匀的γ''沉淀。尽管所有老化样品中的γ''沉淀物的平均尺寸均保持不变，但体积分数随固溶温度的升高而增加。