Mechanistic study of anisotropy elimination in DWAAM-deposited TA15 alloy through coupling of La2O3 addition and low-frequency pulsing strategies

Abstract

The wire arc additive manufacturing (WAAM) process is considered suitable for the fabrication of large-scale components. However, titanium alloys fabricated via this method have been observed to exhibit pronounced mechanical anisotropy. To address this issue, this study used a dual wire arc additive manufacturing (DWAAM) method to quantitatively introduce La₂O₃ particles into the titanium alloy, coupled with low-frequency pulsing strategies to refine the size of the columnar grains in the alloy. From the results, the anisotropic mechanical properties of the titanium alloys deposited by using this coupled strategy were mitigated. The mechanism behind this anisotropy reduction was further investigated. The results reveal that the anisotropic yielding strength is correlated with the orientation distribution of α laths, while the anisotropy in elongation is associated with the spatial arrangement of the α colonies along the columnar grain boundaries. The refinement of the columnar grains of the alloy effectively modified α-lath orientations and balanced the distribution of α colonies, which served as the critical factor in the reduction of mechanical anisotropy. This study provides insights into microstructure regulation for optimizing the isotropic performance of WAAMed titanium alloys.