Orientation and strain-rate effects on high-temperature plasticity of 316 L stainless steel fabricated by laser powder bed fusion

The extremely rapid cooling rates inherent to laser powder bed fusion (LPBF) processing produce unique microstructural features. In LPBF-fabricated 316 L stainless steel (SS316L), the formation of metastable sub-grain structures enriched with dislocations has been directly associated with superior tensile performance at ambient conditions. However, the absence or instability of these substructures at elevated temperatures can significantly alter mechanical behaviour. In this work, the high-temperature deformation response of LPBF-fabricated SS316L is systematically investigated, with particular emphasis on the effects of build orientation and strain rate. Uniaxial tensile tests were conducted along both the vertical (along the build direction) and horizontal (perpendicular to the build direction) orientations at a temperature of 850 °C under multiple strain rates. At room temperature, plasticity was primarily accommodated by dislocation slip and deformation twinning, whereas at elevated temperatures, a transition was observed, with dynamic recrystallisation becoming the dominant mechanism, especially in horizontally built specimens. However, the vertical samples retained elongated grains and exhibited comparatively limited recrystallisation. The tensile response demonstrated strong dependence on both strain rate and build orientation. The experimental findings, corroborated by crystal plasticity modelling, provide important insights into the orientation- and temperature-dependent plasticity mechanisms of LPBF SS316L. The applied model is capable of accurately predicting the high-temperature mechanical response by incorporating various temperature-dependent mechanisms.