Study on special grain boundary distribution of Σ3ⁿ in micron selective laser melting of 316L stainless steel during tensile deformation

In this paper, electron back scatter diffraction (EBSD) technique was used to study the grain boundary characteristic distribution of 316L stainless steel transverse tensile samples and normal tensile samples prepared by micron selective laser melting under 8%, 18% and 28% tensile strain. The results show that with the increase of tensile strain, the proportion of Σ3 grain boundaries of transverse and normal samples increased significantly, while the proportion of Σ9 and Σ27 grain boundaries decreased significantly. The connectivity of general high angle grain boundary network was effectively interrupted by Σ3 grain boundaries. The coherent/incoherent characteristics of special grain boundaries were measured by micro rectangular section method. When the transverse specimen was under 18% tensile strain, the special grain boundaries were mainly Σ3_IC, accounting for about 60%. Under the same conditions, the special grain boundaries of normal tensile specimen were mostly Σ3_C, accounting for about 73%. Further analysis pointed out that the migration of incoherent Σ3_IC grain boundaries and the interaction with Σ9 grain boundaries were the reasons for the increase of the proportion of Σ3 special grain boundaries during the tensile strain.