Additive Processing of Ti‐17 by Wire Arc Directed Energy Deposition: An Investigation of the Microstructure and Mechanical Properties

This study investigates the processing of Ti‐17 by wire arc directed energy deposition. The investigation focused primarily on the microstructure and mechanical properties in both the as‐built and heat‐treated states. Significant microstructural banding is observed in the as‐built state as a consequence of the process intrinsic heat treatment. A strong correlation is identified between the position within each band and the α lamellae width and subsequently the hardness (a spread of up to 133 HV1 was observed). The mechanisms involved in developing the microstructural bands are discussed, and a proposed pathway for their formation is presented. In tensile tests, the processed Ti‐17 outperformed the conventional alloy in terms of strength (exceeding 1100 MPa), but lacked ductility in both the as‐built and heat‐treated state. The main reason for the low ductility is identified as a continuous film of α phase (GBα) at the grain boundary of prior β grains. Conventional heat treatment resulted in the growth of existing GBα, thereby proving ineffective. The observed anisotropy in the tensile properties between the build‐up and deposition directions is found to be closely related to the loading direction of GBα at prior β grain boundaries.