Effect of the Surface State of Steel on the Microstructure and Mechanical Properties of Dissimilar Metal Lap Joints of Aluminum and Steel by Friction Stir Welding

摘要

Friction stir lap joints of AC4C Al alloy (top sheet) and steel (zinc-coated steel, brushed finish steel, and mirror finish steel) were produced when the friction stir welding tool did not touch the lower steel surface. For zinc coat steel, the strength of joints could reach 97.7 pct of that of steel; for brushed finish steel, the strength was 63.2 pct of that of steel; for mirror finish steel, Al alloy and steel could not be welded. The effect of the surface state of steel on the microstructure and mechanical properties of dissimilar metal friction stir lap joints of AC4C Al alloy and steel was discussed.