The effect of processing parameters on dislocation density and tensile properties in laser powder bed fusion 316L

Abstract

The processing-structure-properties relationships in laser beam powder bed fusion (PBF-LB) additive manufacturing (AM) are complex with multiple aspects of the processing impacting the microstructure and mechanical properties. Though, the influences of process parameters on strengthening mechanisms are less clear. In this work, laser power, scanning velocity, and hatch spacing were varied to promote PBF-LB 316L microstructures with distinctive thermal histories to vary microstructures and tensile properties. Tensile data were collected for over 100 different processing parameters on a single PBF-LB platform. Across the process parameter matrix yield strength, work hardening behavior, and ductility varied considerably. In this work, the effect of process parameters on initial dislocation density was studied. By quantifying the dislocation density with X-ray diffraction and line profile analysis, a relationship between processing parameters and initial dislocation densities was established. The contribution of dislocation density and other strengthening mechanisms to the yield strength is discussed.