Alpha texture induced fracture mechanism of laser directed energy deposited Ti-6Al-2Zr-1Mo-1V alloy with changing directions

In this study, a TA15 alloy with dual deposition direction was prepared by changing deposition direction using laser directed energy deposition technology. The new direction was 45° from the original direction, and each deposition zone exhibited the columnar grains with major axes parallel to each deposition direction. A large amount of grain boundary α phase (α_GB) appeared at the interface where the deposition direction was changed. Tensile test results showed that the fracture location of tensile specimen was far away from the interface, indicating the reliability of the interface bonding. The slip system of α phase in fractured region was in an easily-activated orientation with a high Schmid factor for loading direction, resulting in a lower strength in this region. Strong plastic deformation occurred in this region and caused fracture, indicating that α texture is the main factor leading to fracture rather than α_GB.