The Ti6Al4V alloy sandwich structure is made by LBW/SPF/DB process. The evolvement of the microstructure in the LBW area is investigate before and after SPF/DB process. The results indicate that

during the SPF process

the orientation of the β grain changeds gradually towards the tension direction and the fi ne lamellar structure formed which enables the hardness of the welded joint to be reduced but the plasticity increased can bear the combination of the bending and the tension stresses. The crystal grain of the as-received Ti6Al4V alloy remains equiaxed but larger after SPF/DB process and the needle-like α phase is coarser in the central area of the welded joint and the coarse Widmanstaten structure exists in bilateral areas of the welded joint centre and in the heat-affected zone the needle-like α′ phase transforms into short and small α banding.