Experimental study of Ti/Al impact spot welding by intense laser pulse induced shock waves

A novel laser impact spot welding process is proposed, during which solid state and metallurgical bonding of similar or dissimilar metal combinations can be obtained. In the experiment, the laser pulse is launched from a Nd:YAG laser to induce the Ti foil in the thickness of 30 μm to bulge and collide to the 100 μm thickness Al plate with high speed to get spot joint. When the standoff distances of the Ti foil are 0.3, 0.6, 0.9 mm, respectively, the springback area at the center of the weld spot decreases, and the bonding area increases gradually. The cold inlaid technique is used to fix the weld examples for studying the cross-sections features of the weld spot, and wavy interface with the alterative amplitude and period along the diameter direction of the weld spot and the straight weld interface are observed. In order to investigate the influence of laser impact spot welding on the mechanical properties of the materials in the weld zone, the nanoindentation hardness test is applied across the weld interface. It is found that the microhardness in the weld interface region increases obviously. Moreover, the results lap shear strength test show the bonding strength of weld spot is relatively fine when effective solid-state and metallurgical bond is obtained during welding, and the failure usually occurs at the edge of the weld spots. Laser impact spot welding provides a new way for dissimilar metal foils welding in the thickness of micro level.