Simultaneous enhancement of strength and ductility in selective laser melting manufactured 316L alloy by employing Y2O3 coated spherical powder as precursor

Abstract

In this work, the 316L spherical powders coated with homogeneous Y2O3 layer have been prepared by in-situ chemical method. Then the influence of Y2O3 on the microstructure and mechanical properties of 316L specimens prepared by selective laser melting was studied. It was found that the grain morphology and crystallographic texture of the SLMed 316L specimens with different Y2O3 contents show the same anisotropy along the vertical direction and horizontal direction, which is independent of the doping content of Y2O3. The formation of twins in specimens doped with Y2O3 can be attributed to the combined effects of large residual stress, low stacking fault energy and in-situ heat treatment. Compared with the strength (707 ± 3 MPa) and ductility (42.5 ± 0.3%) of the undoped 316L specimen, the strength (732 ± 5 MPa) and ductility (49.5 ± 0.8%) of the 316L specimen doped with 0.25 wt% Y2O3 is improved simultaneously. The increase of strength is mainly attributed to the formation of twins, the strengthening mechanism caused by the precipitated particles and the refinement of cellular structures. The high ductility is attributed to the influence of the refinement of cellular structures and the formed twins.