Residual Stress in Additively Manufactured Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo Alloys

Additively manufactured titanium components inherently develop residual stresses during the build process, which can adversely affect mechanical performance—particularly dwell fatigue resistance—and promote defects such as delamination, cracking, and dimensional distortion. In this study, we utilized neutron diffraction and the slitting method, a relaxation-based residual stress measurement technique, to investigate the influence of interlayer delay on residual stress evolution in Ti-6Al-4V wall structures. We further examined the role of martensitic phase formation in the development of residual stresses in as-built Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo components. Results indicate that interlayer delay has a minimal impact on the residual stress magnitude in single-track wall configurations. However, the type of martensitic phase present in the microstructure significantly influences the residual stress state. Furthermore, the normal stresses were primarily concentrated at the edges of the wall, while the peak longitudinal stresses were observed along the centerline at the wall–substrate interface. Additionally, in situ synchrotron X-ray diffraction during multipass laser scans revealed that spatial variations in thermal cycling within a deposited layer can lead to mesoscale residual stress formation in LHW-DED Ti-6Al-4V structures.