Effect of beam oscillation on fatigue life of Ti–6Al–4V electron beam weldments

The present study deals with the effect of beam oscillation technique using elliptical waveform on fatigue life of Ti–6Al–4V electron beam weldments. Autogenous full penetration bead-on-plate electron beam welds were made with and without beam oscillation. Some welds were subjected to post-weld heat treatment (PWHT) at two different temperatures (700 and 900 °C). Room temperature hardness, tensile properties and fatigue life of the weldments in the as-welded and PWHT conditions were studied and correlated with the microstructure. The beam oscillated weldments exhibited lower strength (hardness) compared to those made without beam oscillation. This was attributed to wider diffusional α plates in the beam oscillated welds due to lower cooling rates. The beam oscillated weldments exhibited inferior fatigue lives compared with unoscillated weldments owing to the presence of wider α platelets in the former. As the width of α platelets in the weldments subjected to PWHT at 700 °C was smaller than that in the weldments subjected to PWHT at 900 °C, they exhibited longer fatigue lives.