Towards superior fatigue crack growth resistance of TC4-DT alloy by in-situ rolled wire-arc additive manufacturing
Yifeng Gao, Chuandong Wu, Ke Peng, Xinli Song, Youheng Fu, Qingyong Chen, Mingbo Zhang, Guilan Wang, Jing Liu
Abstract
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-β heat treatment. Sample S2 had superior fatigue crack growth resistance, which is mainly attributed to its finer defects and finer α 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 (∼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.