Crystallographic-orientation-dependent tensile behaviours of stainless steel 316L fabricated by laser powder bed fusion

Abstract

In the present study, single-crystalline-like bulk stainless steel (SS316L) specimens with a {110} <001> Goss texture were produced by laser powder bed fusion (LPBF). The tensile behaviours of the LPBF-fabricated SS316L along the <100>, <110> and <111> crystallographic directions were systematically investigated. The samples along the three crystallographic directions enabled a broader strength-ductility paradigm of LPBF-fabricated SS316L and exhibited a superior strength-ductility synergy over their traditionally manufactured counterparts. The tensile responses of the SS316L samples were highly dependent on their crystallographic orientations. The <111> orientated samples exhibited higher yield strength (YS) than those of the <100> and <110> orientated samples, which was mainly attributed to the lower Schmid factors of the <111> grains along their tensile axes (TAs). The dominant deformation mechanisms were found to be dislocation slip and deformation twinning for the <100> and <111> orientated samples, respectively. For <110> orientated samples, significant deformation twinning as well as evident lattice rotation were observed simultaneously. The higher tendency towards deformation twinning of the <110> and <111> orientated samples arose from the larger separations between the partial dislocations in these samples, which reduced the effective stacking fault energies as well as the critical stresses for deformation twinning significantly. Due to the higher propensity towards deformation twinning, the <110> and <111> orientated samples showed better ductility over the <100> orientated samples by facilitating twinning-induced plasticity (TWIP) effect. Furthermore, the lattice rotation of the <110> samples during tension featured a modest TWIP effect which enabled a more prolonged strain hardening rate uphill than that of the <111> samples, resulting in a superior ductility with a total elongation (TE) of ~100 %.