High-resolution reciprocal space mapping reveals dislocation structure evolution during 3D printing

Dislocation structures are ubiquitous in any 3D printed alloy and they play a primary role in determining the mechanical response of an alloy. While it is understood that these structures form due to rapid solidification during 3D printing, there is no consensus on whether they evolve due to the subsequent solid-state thermal cycling that occurs with further addition of layers. In order to design alloy microstructures with desired mechanical responses, it is crucial to first answer this outstanding question. To that end, a novel experiment has been conducted by employing high resolution reciprocal space mapping, a synchrotron-based X-ray diffraction technique, in situ during 3D printing of an austenitic stainless steel. It reveals that dislocation structures formed during rapid solidification undergo significant evolution during subsequent solid-state thermal cycling, in particular during addition of the first few (up to 5) layers above the layer of interest.