Electrode-embedded linear actuating enhanced resistance spot welding of aluminium alloy and dual phase steel

Resistance spot welding (RSW) of aluminium/steel dissimilar materials has important application prospects in industries such as automobiles. However, the relatively poor mechanical properties of the welds due to the issue of brittle intermetallic compounds (IMCs) at the welding interface has been the major concerned by the welding community. A novel modified RSW process that utilizes relatively high-frequency linear actuator embedded in the electrode is proposed and experimentally verified. The linear actuator superimposes a pulsed electrode force to base force which is expected to facilitate the melt flow inside the aluminium nugget and modify the forming process of the IMCs. The experimental results demonstrate that the introduction of linear actuating could significantly increase the area of the aluminium nugget, which means more aluminium was melted. Further, it is observed that the thickness of the IMCs layer was reduced by 81.9 %, with a peak thickness of 1.48 μm. Therefore, 38.5 % improvement in the average peak tensile shear load of the welded joints was achieved. The involved mechanisms were discussed by thermal/force dynamic analysis.