Development of in-situ rolling Ti-6Al-4V in direct energy deposition

The purpose of this thesis was to develop a novel in-situ rolling system for Ti-6Al-4V to address the longstanding issues in direct energy deposition (DED), such as large columnar grains. Using this novel in-situ rolling process, this PhD work successfully established a considerably finer microstructure, enhanced tensile properties, and improved high cycle fatigue performance in DED Ti-6Al-4V. Additionally, for the first time, a disputed phase in the AM titanium alloy is resolved through extensive characterizations. The effectiveness of this novel technique in improving the overall performance of DED Ti-6Al-4V, as well as the scientific insights acquired from this study, will contribute to the rapid adoption of AM in the industry.