Towards superior fatigue crack growth resistance of TC4-DT alloy by in-situ rolled wire-arc additive manufacturing

Titanium alloys have many advanced applications where they are subject to fatigue. Here, we compare the fatigue crack growth resistance and microstructures of TC4-DT alloys fabricated by wire-arc additive manufacturing (WAAM; sample S1) and in-situ rolled WAAM (sample S2) followed by quasi-b heat treatment. Sample S2 had superior fatigue crack growth resistance, which is mainly attributed to its finer defects and finer a phase. The critical size of the defects related to fatigue performance was calculated. The majority of defects in sample S2 were smaller than the critical size, while several coarse defects (similar to 1.91 mm) were observed in sample S1. Multiple secondary cracks could be detected near the fracture surface in sample S2, leading to long and tortuous fatigue crack propagation paths. Therefore, in-situ rolling can improve the fatigue properties of titanium alloys fabricated by additive manufacturing. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).