Microstructure formation and transformation during electron beam selective melting (EBSM) is a unique process that has rarely been investigated, but can significantly influence the mechanical properties of parts. In this study, defect-free IN939 superalloy specimens were prepared and characterized using the EBSM method. It was found that the microstructures of the EBSM IN939 specimens consisted of primary, middle, and coarse γ' phases, and the ƞ phases had a gradient attribute. Transmission electron microscopy, selected-area electron diffraction, and energy dispersive spectroscopy tests were performed at different specimen heights, as well as a series of tensile tests. The results showed that the yield strength was influenced by the gradient microstructure. Higher yield strengths were obtained at the top of the fabricated specimens. Post-treatment was adopted to homogenize the gradient microstructure. Fracture analyses after the tensile test demonstrated the effects of different strengthening phases on the fracture behavior.

电子束选择性熔化 (EBSM) 过程中的微观结构形成和转变是一种很少被研究的独特过程，但会显着影响零件的机械性能。在这项研究中，使用 EBSM 方法制备和表征了无缺陷的 IN939 高温合金试样。发现EBSM IN939试样的显微组织由初生、中、粗γ'相组成，ƞ相具有梯度属性。在不同的试样高度上进行了透射电子显微镜、选区电子衍射和能量色散光谱测试，以及一系列拉伸测试。结果表明，屈服强度受梯度显微组织的影响。在制造的试样顶部获得了更高的屈服强度。采用后处理使梯度微观结构均匀化。拉伸试验后的断裂分析证明了不同强化阶段对断裂行为的影响。