The fabrication of the compositionally graded metals provides a new frontier in additive manufacturing and the characterization of the elemental distribution of graded materials is strongly desired for the quality control of powder mixing and improvement of additive manufacturing process parameters. In this study, Micro-beam X-ray fluorescence (μ-XRF) was used to characterize the elemental distribution of additive-manufactured compositionally graded stainless steel on a large area. A poly-capillary X-ray optics unit was used to obtain a high spatial resolution with the spot size of 20-μm. The quantitative distribution characterization of Ni, Mo, Cr, Mn, Si and Cu elements in the whole deposition direction have been realized through the improvement of μ-XRF quantitative calibration method by using certified reference materials with composition and microstructure similar to the graded sample. The composition distribution variation in different cladded layer was also investigated with the pixel distance decreased to 20 μm. Moreover, laser-induced breakdown spectroscopy was used to analyze the composition distribution of the composition-graded steels to verify the reliability of quantitative distribution characterization results by μ-XRF method. The elemental distribution results from two methods have good agreement, but the results determined by μ-XRF can give more details about the composition distribution in different cladded layers because of its higher spatial resolution, which is closely related to additive manufacturing process. The microstructure content varied linearly with the change of composition. The austenite volume fraction increased with an increase in Ni content and the evolution rule of the structure agreed with the calculated thermodynamics model results. Cracks appeared in the martensite and austenite transformation region with a large volume change when the Ni content ranged between 6.5% and 8.5% for the gradient stainless steels.

成分梯度金属的制造为增材制造提供了新的前沿，并且对于粉末混合的质量控制和增材制造工艺参数的改进，强烈需要对梯度材料的元素分布进行表征。在这项研究中，微束 X 射线荧光 (μ-XRF) 被用于表征大面积增材制造的成分梯度不锈钢的元素分布。使用多毛细管 X 射线光学单元获得高空间分辨率，光斑尺寸为 20 微米。Ni、Mo、Cr、Mn、通过对μ-XRF定量校准方法的改进，使用成分和微观结构与分级样品相似的有证标准物质，实现了整个沉积方向的Si和Cu元素。随着像素距离减小到 20 μm，还研究了不同熔覆层的成分分布变化。此外，利用激光诱导击穿光谱分析成分分级钢的成分分布，验证μ-XRF法定量分布表征结果的可靠性。两种方法的元素分布结果具有很好的一致性，但 μ-XRF 确定的结果由于其更高的空间分辨率，可以提供有关不同熔覆层中成分分布的更多细节，这与增材制造工艺密切相关。显微组织含量随成分的变化呈线性变化。奥氏体体积分数随着Ni含量的增加而增加，组织演化规律与热力学模型计算结果一致。当Ni含量在6.5%~8.5%之间时，梯度不锈钢在马氏体和奥氏体相变区出现裂纹，体积变化较大。