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
Year: 2022
Type: article
Abstract: The 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.
Institutions: University of Manchester, Cranfield University
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,390
Awards: G1015058392, G2158237762, G2703599441, G2996304452, G3146101534, New Wire Additive Manufacturing (NEWAM), G3305536412, LightForm: Embedding Materials Engineering in Manufacturing with Light Alloys, Sir Henry Royce Institute - Manchester and NNL Equipment, G504327055, G5424142534, G5432890613, Sir Henry Royce Institute - Manchester Build, G6078643358, The Royce: Capitalising on the investment, G6989197718, G708391930, G7204459864, G7445816383, G7514479249, G7594288067, Sir Henry Royce InsStitute - recurrent grant, G87373762
OpenAlex ID: W4296901009