Evolution of site-specific solidification microstructure and texture during additive manufacturing of stainless steel 316L by laser powder bed fusion

Abstract

The present investigation addresses the evolution of microstructure and texture due to site-specific solidification conditions in additively manufactured stainless steel 316L by Laser Powder Bed Fusion (LPBF) technique. Experiments were designed with increasing dimensionality from 1D to 3D that simulates and deconvolutes the different factors influencing the solidification conditions during additive manufacturing. At locations near to substrate, the large thermal gradient, the repeated heating/cooling cycle and the influence of overlapping region due to melt pool results in the formation of significantly high dislocation density, anisotropic columnar morphology of grains, and crystallographic texture consisting of 〈100〉 and 〈110〉 fibers along the building direction. In contrast, the availability of multiple heat flow direction combined with decreased intensity of heating/cooling cycle is experienced at the top region, that results into comparatively lesser dislocation density, decreased anisotropy and formation of 〈111〉 and other non-trivial texture fibers. To some extent, the solution annealing treatment eliminated the heterogeneities related to grains morphology and dislocation density, however, texture remains unaffected.