Effect of the forging pressure on the microstructure and residual stress development in Ti–6Al–4V linear friction welds

A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and residual stress development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the residual stress development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and residual stresses and weld microstructure, whereby the residual stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.