On the microstructure and tensile properties of Inconel 718 alloy fabricated by selective laser melting and conventional casting

Abstract

In this work, we investigated the microstructure and tensile properties of Inconel 718 alloy processed by selective laser melting (SLM) and conventional casting technique using multiscale characterization methods. Results indicated that a columnar grain structure containing cellular structure units with submicron size was the major feature in the as-printed Inconel 718 alloy. At the cellular structure boundaries, the high-density dislocation tangles, segregation of Nb/Mo atoms and nano-sized Laves phases were found. Meanwhile, we also observed dislocation pile-ups and stacking faults in the interior of the cellular structure. In contrast, in the as-cast Inconel 718 alloy, both the grains and Laves phases were much coarser. Discrete dislocations, dislocation tangles and [Formula: see text]” precipitates were locally observed in the grains. Tensile results showed the as-printed Inconel 718 alloy had a higher strength and a lower elongation in comparison with those in the as-cast alloy. Based on the experimental results, the formation mechanism of the cellular structure was discussed.