In-situ monitoring of Inconel 718 phase evolution during DMD

Cyclic heating and rapid melting/solidification mechanism cause complex thermal gradients during direct metal deposition (DMD) of Inconel 718 changing dynamically in time and region within the bulk material. These changes can trigger repetitive phase transformations and evolutions along the build height of the part inducing microscopic and macroscopic strains. In order to decouple and disclose contributions (microstructural, thermal, residual stresses) of the overall stress state, phase and lattice parameter evolution needs to be monitored during printing. The commonly used techniques for characterization are not adequate for resolving phase development due to the lack of time and spatial resolution. Hence, a time-resolved in-situ DMD of wire Inconel 718 via synchrotron x-ray diffraction at ID31 is hereby proposed. This study will disclose the solidification sequence at regions of interests (including melt pool) and its phase and lattice parameter evolution during continuous printing.