DOE OSTI2019
In additive manufacturing (AM) processes, materials are selectively added in layer-wise fashion to build three-dimensional objects. This approach provides several advantages over conventional manufacturing, including the ability to manufacture complex parts, design flexibility, shorter lead times, reduced inventory of spares, and on-demand manufacturing [1]. With these advantages, applications of AM are increasing rapidly in the medical, aerospace, automobile, and defense industries [2, 3]. Currently, laser powder bed fusion (LPBF) is the most extensively used AM technique for manufacturing metal parts. In a typical LPBF process, a high-power laser beam is scanned across a thin layer of powder, melting and subsequently fusing it to the previous layer. Highly transient interactions between the laser, powder particles, and the bottom layer lead to defects in the AM materials. These defects include porosity, residual stresses, surface roughness, and undesirable microstructures [1, 4]. Additionally, several in situ techniques have been developed to capture these interactions in real time, including high-speed visible light and infra-red imaging [5]. However these techniques are limited to surface observations. Most of the important phenomena that govern the quality of the AM parts, such as dynamics of the vapor depression and melt pool, occur sub-surface and hence cannot be captured using traditional optical techniques. Recently, a synchrotron-based high-speed X-ray imaging technique has been developed to record the sub-surface dynamics of metallic materials during the LPBF process. The unprecedented spatial and temporal resolutions afforded by the synchrotron sources allow direct observation of many important phenomena in AM for the first time [6–9]. Further, high-speed X-ray diffraction and optical imaging techniques are also being applied to capture the crystallographic and thermal information of the material, respectively, as they undergo melting, solidification, and cooling [6, 9]. In this contribution, we introduce the recent developments at the Advanced Photon Source (APS) for in situ and operando study of LPBF processes.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗