Comparative Study of the Ultrafine-Grained Structure 316L Stainless Steel and Ti-6-4 Alloy Produced by Selective Laser Melting

Abstract

Selective laser melting (SLM) of powders is a promising technology to produce part with complex shape. The structure features is of great interest for many researches because metallic materials produced by SLM technology demonstrate rather high mechanical properties. Thanks to the ultra-fast crystallization during SLM process, the created parts should have an ultrafine grained or amorphous structure. Based on the obtained data, it can be concluded that the observed ultrafine-grained structure and crystalline anisotropy can be arised from the rapid motion of the laser beam, resulting in significant temperature gradients and high cooling rates. Formation of dendritic and columnar microstructure is typical for crystallization processes occurring at high temperature gradients. In the present study the EBSD maps, crystalline structure features of the 316 austenitic stainless steel and titanium alloy Ti-6-4 are presented. The dependencies of the mechanical properties on the specific energy input during SLM process are discussed. The main assumption is that during SLM it is possible to produce metallic material with subgrain structure 0.7 – 0.9 mcm, which is promising for further investigation of superplasticity.