Oxide dispersion strengthened stainless steel 316L with superior strength and ductility by selective laser melting

Dense oxide dispersion strengthened (ODS) 316 L steels with different amount of Y2O3 additions were successfully fabricated by selective laser melting (SLM) even though part of the added Y2O3 got lost during the process. The microstructure was characterized in details and the mechanical properties were tested at room temperature, 250 degrees C and 400 degrees C, respectively. The effect of the scanning speed on agglomeration of nanoparticles during SLM process was discussed. Superior properties, e.g., yield strength of 574 MPa and elongation of 91%, were achieved at room temperature in SLM ODS 316 L with additional 1% of Y2O3. At elevated temperatures, the strength kept high but the elongations dropped dramatically. It was observed that nano-voids nucleated throughout the whole gauge section at the sites where nanoinclusions located. The growth and coalescence of these voids were suppressed by the formation of an element segregation network before necking, which relieved local stress concentration and thus delayed necking. This unusual necking behavior was studied and compared to the previous theory. It appeared that the strong convection presented in the melt pool can evenly redistribute the short-time milled coarse Y2O3 precursor powder during SLM process. These findings can not only solve the problems encountered during the fabrication of ODS components but also replenish the strengthening mechanism of SLM 316 L thus pave a way for further improving of mechanical properties. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.