Cellular size dependence on the strength of additively manufactured austenitic stainless steel

The sub-micro cellular structure is a particular phenomenon in many laser powder-bed fusion (LPBF) metals and alloys. In this work, LPBF 316L SSs with different cellular sizes were fabricated under various scanning speeds. Results demonstrate that increasing the scanning speed will decrease the cellular size due to the increased cooling rate, and the maximum cooling rate under 7000 mm/s is ten times higher than that of under 250 mm/s in LPBF 316L SSs as confirmed by finite element modeling. Both dislocation enrichment and elemental segregation (Mo and Cr) at the cellular boundary contribute to the high strength of the LPBF parts; however, nano-indentation tests indicate that the blocking ability of the cellular structure for dislocation motion is weaker compared with the typical grain boundary. (c) 2020 Elsevier B.V. All rights reserved.