Non-equilibrium dynamics in additive manufacturing through operando X-ray studies

Dynamic solidification behavior during metal additive manufacturing (AM) directly influences the as-built microstructure, defects, and mechanical properties of printed parts. How the formation of these features is driven by temperature variation (e.g., thermal gradient magnitude and solidification front velocity) has been studied extensively in AM, with synchrotron x-ray imaging becoming a critical tool to monitor these processes. Here we extend these efforts to monitoring full thermomechanical deformation during solidification and formation of metastable phases through the use of operando x-ray diffraction during laser melting.

In the first example, I will highlight how thermomechanical deformation modes such as torsion, bending, fragmentation, assimilation, oscillation, and interdendritic growth can be analyzed with operando diffraction data. In the second example, I will show how the formation of metastable phases during AM can have a significant effect on the microstructure of printed parts. Understanding such phenomena can aid the optimization of printing strategies to obtain specific microstructural features, including grain morphology, localized misorientations, dislocation substructure, and grain boundary character.