Strain rate-dependent tensile response and deformation mechanism of laser powder bed fusion 316L stainless steel

Abstract

The laser powder bed fusion (LPBF) process is renowned for producing metal parts with exceptional mechanical properties, attributed to their unique microstructures. However, there is a lack of discussion in the literature regarding the plastic deformation mechanism at wide strain rates. To address this research gap, this study employs both quasi-static tensile (QST) tests and dynamic Split-Hopkinson tensile bar (SHTB) experiments to investigate the tensile properties and deformation mechanisms of a well-characterized material, 316L stainless steel (SS), across an extensive range of strain rates spanning from 10−3 s−1 to 103 s−1. Our results reveal the superior quasi-static and dynamic stretching behavior exhibited by LPBF specimen in comparison to the wrought 316L counterpart. This enhanced behavior can be primarily attributed to the cellular and hierarchical structures inherent to LPBF specimen. Notably, the cellular structure emerges as the primary controlling factor in mechanical deformation due to its capacity for increasing the critical strain required for deformed twinning and martensite transition. Consequently, under quasi-static loading, twinning and martensite transition act as the dominant deformation mechanism, while dynamic loading conditions are characterized by a prevalence of dislocation interactions. This comprehensive understanding of the deformation mechanism and strain rate-dependent behavior of LPBF 316L SS provides valuable insight for optimizing its mechanical properties under a wide range of loading conditions.