Influence of post-deposition aging treatment (PDAT) on microstructural and mechanical properties of wire arc directed energy deposited Ti6Al4V thin wall

Purpose This study aims to address the challenges of adopting directed energy deposition (DED) for manufacturing large-scale Ti6Al4V components due to anisotropic properties in the as-deposited (AD) condition. The research investigates whether post-deposition aging treatment (PDAT) can homogenize the properties of Ti6Al4V produced by wire arc DED (WA-DED). Design/methodology/approach Three thin wall samples fabricated using WA-DED were subjected to PDAT at three different temperatures – 480°C (T1), 530 °C (T2) and 580 °C (T3) – for 8 h, following an initial solutionizing step at 950 °C for 1 h. The study analyzes grain orientation, grain alignment, α-lath size, dislocation density, α′ fraction and anisotropy of strength and elongation across these PDAT conditions. Findings The results show that PDAT alters α-Ti grain orientation from <−12–10> at T1 to <−12–11> and <0001> at T2, whereas β-Ti orientation shifts from <100> in the AD and T1 conditions to <100> at (001) beyond 530 °C. PDAT and higher temperatures increase α-lath size from 10 to 12 µm, well above the 4.53 µm size in the AD condition. Dislocation density decreases from 7 × 10 –4 [ ] to 4 × 10 –4 nm −2 as temperature increases, lower than the AD value of 8 × 10 –4 nm −2 . The α′ fraction drops to 23% with increased aging temperature, down from 42% in AD. Mechanical anisotropy in yield and ultimate strength decreases to 5% and 3% by T2 but spikes at T3. Elongation anisotropy rises from 4% at T1 to 18% at T3, with T2 showing minimal strength anisotropy compared to AD, whereas T3 exhibits greater anisotropy. Originality/value This study provides new insights into the effects of PDAT on the anisotropic properties of WA-DED Ti6Al4V, offering a potential path to enhance homogeneity in large-scale additive manufacturing applications. The results indicate that optimized PDAT conditions, particularly at T2, may mitigate anisotropic challenges in DED-produced Ti6Al4V components.