J. Mater. Sci. Technol. ›› 2020, Vol. 42: 97-105.DOI: 10.1016/j.jmst.2019.11.004

• Orginal Article • Previous Articles     Next Articles

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

Yuan Zhonga, Leifeng Liub, Ji Zoub, Xiaodong Lic, Daqing Cuia, Zhijian Shena*()   

  1. a Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
    b School of Metallurgy and Materials, University of Birmingham, B15 2TT UK
    c Department of Chemistry-Radiochemistry, P.O. Box 55, FI-00014 University of Helsinki, Finland
  • Received:2019-08-14 Revised:2019-09-30 Accepted:2019-10-07 Published:2020-04-01 Online:2020-04-16
  • Contact: Shen Zhijian

Abstract:

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 °C and 400 °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.

Key words: ODS steel, Selective laser melting (SLM), Elevated-temperature properties, Necking, Strain hardening