Anisotropic cellular structure and texture microstructure of 316L stainless steel fabricated by selective laser melting via rotation scanning strategy

Abstract

In this work, the effects of solidification and remelting under chessboard 67° rotation scanning strategy on the microstructure and properties of selective laser melted (SLMed) 316L stainless steel (316L SS) were studied, including dendrite microstructure, element distribution, grain orientation, dislocation structure, microhardness and corrosion resistance. We put forward a complete foundation relationship among texture, cellular structure and mechanical property influenced by anisotropy. Main results are summarized as follows: The 〈101〉 texture formation is the result of dendrite epitaxial growth. The cellular dislocation structure highly overlapped with dendrite significantly changed in remelting zone. Hence the high ratio of 〈101〉 texture signifies the anisotropy distribution of epitaxially growth dendrite which released the internal stress. The dislocation structure has a contribution to strength similar work hardening strengthening. Meanwhile, the 316L SS obtains Orowan strengthening via the nano oxide pinning effect in dislocation wall. Thus, the dislocation density and oxide distance obvious changed in different directions of cellular dislocation structure, resulting in the cellular dendrite regions performed higher microhardness than the columnar dendrite regions. The drastic change of dendrite increased the crack sensitivity of SLMed 316L SS, and the junction of different epitaxially growth direction dendrites formed high energy grain boundary.

Keywords

• Selective laser melting
• 316L stainless steel
• Texture
• Dendrite
• Microhardness
• Additive manufacturing