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A deposition size monitoring method based on a molten pool’s geometric characteristics, including image calibration, contour extraction, contour coordinate calculation, and deposition size modeling, is established in this study to observe the real-time size of components formed by arc-directed energy deposition (ADED). Image calibration was first performed using the molten pool’s imaging transformation matrix to accurately match the image’s pixels to the actual spatial position. Next, an adaptive threshold segmentation algorithm was applied to extract the contours of the calibrated molten pool’s images. The contour was further completed using breakpoint coordinates and their gradient information. The minimum bounding rectangle algorithm was used to fit the contour coordinates for determining the width and height of a single-pass deposition. A mathematical multi-pass and multi-layer depositional size model was created via the parabolic model and the equal volume algorithm for realizing the deposition size monitoring based on the molten pool images. Finally, the rocket engine shell was manufactured using ADED, and the depositional forming size was observed in real time. The overall average size deviation of the component was within ±2.41 mm, suggesting a high forming accuracy.

TA15 titanium alloy components produced via wire-arc direct energy deposition (WA-DED) face challenges related to grain coarsening, suboptimal mechanical properties, and pronounced anisotropy. To address these issues, the current study employed a dual-wire-arc directed energy deposition (DWA-DED) approach to fabricating the alloys by introducing LaF3quantitatively into the deposition metal using a metal cored wire. The incorporation of LaF3was predicated on the in situ reaction: 6[O] + 6[H] + 2 LaF3= La2O3+ 6HF. This reaction effectively removed [H] and [O] from the molten pool, diminishing the presence of the brittle intermetallic compounds and concurrently enhancing toughness. The addition of LaF3resulted in a notable 56.8% increase in elongation and a 33.1% boost in impact toughness. Moreover, the DWA-DED quantitatively introduced [La], facilitating the precipitation of La2O3particles. This precipitation reduced the size of primary columnar grains (PCGs) and promoted heterogeneous nucleation of α-laths. As a result, the elongation of the PCGs’ boundaries diversified the α phase transformation, resulting in the reduced multiple of uniform density (MUD) along the building direction. As a result, the isotropy ratio between vertical and horizontal directions also increased, underscoring the efficacy of LaF3in mitigating anisotropic behaviour in WA-DEDed titanium alloys.