PROCESS-DRIVEN MICROSTRUCTURE TAILORING DURING ADDITIVE MANUFACTURING OF Ti-6Al-4V

Abstract

**Please note that the full text is embargoed until 02/01/2025** In recent years, additive manufacturing (AM) has attracted the attention of many researchers due to the technology providing opportunities in terms of improved functionality, production repeatability, efficiency, and cost and time issues. While AM techniques made possible the realization of complex geometries, their use in critical applications have faced challenges due to the anisotropic characteristic of AM-built parts. More specifically, non-equilibrium AM processes involve steep temperature gradients and rapid solidification, yielding a unique microstructure, e.g., columnar-shaped grains with preferred texture, in final AM-built products and hence anisotropic mechanical properties. Despite significant studies on improving the microstructure of AM-built parts, it remains a major challenge to create products with more isotropic properties. The practiced approaches include optimizing AM process parameters, remelting of each layer during fabrication, or post-process heat treatments. This has raised a question of whether or not it is possible to perform in-situ layerwise microstructure modifications during AM processes, rather than relying only on process parameters optimization, or post-process heat treatment strategies. If successful, it would be possible to create parts with engineered, more isotropic microstructure and properties, e.g., a part with a relatively harder surface for crack initiation resistance and a relatively soft core for high-impact toughness. In addition, the obtained knowledge and understanding could be employed to perform pre-designed local microstructure modifications on each layer of AM, and create composite parts without the use of two single powders.