Residual stress on Ti6Al4V hybrid and laser welded joints

Ti6Al4V alloy combines mechanical strength, deformability, excellent fatigue and corrosion resistance and high strength to weight ratio. Furthermore, the mechanical behavior remains excellent at high temperature. Such characteristics make this material attractive for numerous applications (structural, aerospace and naval) because of recent improvements in welding techniques (laser, hybrid laser/MIG) that allow realizing high quality titanium welded joints. However some problems related to the welding, as deteriorated material properties, residual stresses and distortions, need further investigations. This paper presents a detailed study on residual stresses of Ti6Al4V butt plates welded by laser or hybrid laser/MIG process. Residual stresses were measured by hole drilling method using electrical strain gage rosettes bonded at different position, in order to evaluate magnitude and distribution of residual stresses along the cord. Residual stresses curves obtained for each type of joint and each welding technique are presented and discussed in terms of transversal residual stresses. Residual stresses were also measured at surface by means of X-ray diffractometer. The aim of this work is to present experimental data related to welding processes in order to confirm the validity of currently procedures or improve them.