Ductility-dip cracking (DDC) is a type of solid-state cracking with corresponding ductility loss that is associated with solidification processes in FCC metals and alloys. The phenomenon typically occurs at 0.5 – 0.7 of the alloy melting point. The prevalence of this type of cracking during the tensile deformation of additively manufactured Inconel 738LC at elevated temperature has been studied. Transmission electron microscopy analysis of Inconel 738LC fabricated by L-PBF revealed the presence Ni, Al and Ti (gamma prime-forming elements) along the high-angle grain boundaries following tensile testing at 900ºC. It is therefore surmised that a thin layer of gamma-prime formed along the grain boundaries in the additively manufactured material and weakened the boundaries, thereby facilitating intergranular ductility-dip cracking.

Samples of pure tungsten with the constricted specimen geometry shown in the figure were fabricated by L-PBF using a substrate pre-heating temperature of 530ºC and scan rotation angles of 90º and 67º. Results indicate that a combination of both substrate pre-heating and a constricted geometry may lead to reduced cracking in samples fabricated using a rotation angle of 67º. The effects of these parameters on material fabricated using a scan rotation angle of 90º, however, appear to be negligible.