Davis, Alec E.Caballero Ramos, ArmandoBiswal, RomaliWilliams, StewartPrangnell, P. B.2022-09-292022-09-292022-09-22Davis AE, Caballero AE, Biswal R, et al., (2022) Comparison of microstructure refinement in wire-arc additively manufactured Ti–6Al–2Sn–4Zr–2Mo–0.1Si and Ti–6Al–4V built with inter-pass deformation, Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science, Volume 53, Issue 11, November 2022, pp. 3833–38521073-5623https://doi.org/10.1007/s11661-022-06811-1https://dspace.lib.cranfield.ac.uk/handle/1826/18494The titanium alloy Ti–6Al–2Sn–4Zr–2Mo–0.1Si (Ti6242) has been deposited for the first time by a directed energy deposition process using a wire and arc system—i.e., wire-arc additive manufacturing (WAAM)—with and without inter-pass machine hammer peening, and its microstructure investigated and compared to the more commonly used alloy Ti–6Al–4V (Ti64). The application of inter-pass machine hammer peening—where each added layer was deformed before deposition—successfully refined the strongly textured, coarse, columnar β-grain structure that is commonly seen in α + β titanium alloys, producing a finer equiaxed grain structure with a near-random α texture. The average grain diameter and texture strength decreased with the peening pitch. When Ti6242 was deposited under identical conditions to Ti64, by switching the alloy feed wire in-situ, the refined β-grain size decreased across the alloy-to-alloy transition reaching on average 25 pct less in Ti6242 than in Ti64. A similar 25 pct scale reduction was also found in the Ti6242 α-lath transformation microstructure. This comparatively greater microstructure refinement in Ti6242 was attributed to the dissimilar alloying elements present in the two materials; specifically, molybdenum, which has a lower diffusivity than vanadium and led to slower β-grain growth during reheating as well as a finer transformation microstructure.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Article1543-1940