Harnessing solid-state thermal cycling to Guide microstructure evolution of Additively Manufactured Metallic Alloys

ongoing

Additive manufacturing (AM) holds the potential to revolutionize the alloy manufacturing sector through its ability to provide unprecedented control over the design of alloy microstructures during manufacturing. However, the main roadblock preventing its widespread adoption is the inability to design microstructures with desired mechanical responses. An AM process results in the formation of hierarchical microstructures that are extremely sensitive to the process parameters. Minor changes to these parameters can result in very different microstructures that exhibit significant differences in their mechanical response at multiple length scales. Controlling the mechanical response of hierarchical microstructures requires first understanding their formation during the AM process. Current experimental and modeling research efforts are heavily focused on studying the role of melt-pool dynamics and rapid solidification during the AM process. This project aims at tackling the crucial missing link, which is the microstructure evolution occurring during the long period after solidification and till the end of an AM process, i.e. during Solid-State Thermal Cycling (SSTC), at varying temperature rates and amplitudes. Using novel experimental procedures involving electron microscopy and x-ray synchrotron studies, I will quantify microstructural changes and identify micro-mechanisms caused by SSTC. This will be complemented with development of novel models at intragranular and polycrystalline levels to gain a comprehensive understanding of the role of transient thermal gradients on microstructure evolution. The experiment-modeling synergy will then be harnessed to tailor AM process parameters and suggest in-process/post-process routes to engineer AM microstructures. The approaches developed and the knowledge gained from this project will have far reaching benefits including, but not limited to, guiding emerging solid-state AM technologies such as additive friction stir.