In this study, an Inconel 718 alloy was prepared by selective laser melting (SLM) with a pre-alloyed powder, and the microstructure and mechanical behaviour of the fabricated parts were studied. First, the settled layer structure, composed of several interlaced "perlage" molten pools and molten channels, was captured by low-magnification optical microscopy (OM), and the formation mechanism was revealed by the Gaussian heat source distribution characteristics of the laser source used for the SLM fabrication. Second, high-magnification scanning electron microscopy (SEM) captured the different crystal structures in different fabricated positions; meanwhile, the "cross-border growth phenomenon" along the forming direction and the "growth and distribution characteristics of the crystal" in the radial direction (perpendicular to the forming direction) were also captured. By introducing the component super-cooling theory, the growth mechanism of crystal structures in different positions under a multi-dimensional temperature gradient heat conduction coupling mode is proposed. Finally, combined with transmission electron microscopy (TEM) and a mechanical properties test, it was found that the mechanical properties were between those of parts fabricated by casting and those by forging because the γ" phase and γ' phase were distributed in the crystal, while the carbide phase and Laves phase were distributed in the intercrystal region.

在这项研究中，通过选择性激光熔化（SLM）和预合金粉末制备了Inconel 718合金，并研究了所制造零件的显微组织和力学性能。首先，由低倍光学显微镜（OM）捕获由几个交错的“ perlage”熔融池和熔融通道组成的沉降层结构，并通过所用激光源的高斯热源分布特征揭示其形成机理。用于SLM制造。其次，高倍扫描电子显微镜（SEM）在不同的制造位置捕获了不同的晶体结构。同时，沿形成方向的“跨界生长现象”和“晶体的生长和分布特征” 沿径向（垂直于成形方向）的方向也被捕获。通过引入成分过冷理论，提出了多维温度梯度导热耦合模式下不同位置晶体结构的生长机理。最后，结合透射电子显微镜（TEM）和力学性能测试，发现力学性能介于铸造零件和锻造零件之间，因为γ“相和γ'相分布在晶体中，碳化物相和拉夫斯相分布在晶间区域。提出了多维温度梯度导热耦合模式下不同位置晶体结构的生长机理。最后，结合透射电子显微镜（TEM）和力学性能测试，发现力学性能介于铸造零件和锻造零件之间，因为γ“相和γ'相分布在晶体中，碳化物相和拉夫斯相分布在晶间区域。提出了多维温度梯度导热耦合模式下不同位置晶体结构的生长机理。最后，结合透射电子显微镜（TEM）和力学性能测试，发现力学性能介于铸造零件和锻造零件之间，因为γ“相和γ'相分布在晶体中，碳化物相和拉夫斯相分布在晶间区域。