In this study, the microstructures and mechanical properties of laser direct energy deposition processed AISI 316L with the addition of Hf and Ce were investigated. The microstructures were characterized by optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. The mechanical properties were evaluated via tensile tests. The addition of Hf resulted in grain sizes similar to or slightly larger than those of the 316L alloy, and the presence of Hf agglomerates led to only marginal changes in the mechanical properties. In contrast, the addition of Ce produced significant grain and cellular structure refinement, accompanied by an increase in elongation of approximately 10%. In the microstructures, Ce oxides were not retained within the matrix but instead floated to the surface or were ejected as a spatter. Ce addition promoted grain and cellular structure refinement and ductility through its dynamic oxide behavior in the melt pool during laser deposition.
Park et al. (Sun,) studied this question.