Friction stir spot welding of dissimilar ABS and PA6 by a tool with newly designed tooth-shaped flat pin

Abstract

Dissimilar Acrylonitrile Butadiene Styrene (ABS) and Polyamide 6 (PA6) are hard to be welded due to their poor compatibilities. In this paper, a flat-pin tool with long tooth-shaped tip was designed and utilized to friction stir spot weld ABS and PA6 plates. Annular PA6 anchor and column were produced, which enhanced the mechanical interlocking between the lapped sheets. Rotational speed (S R ) was found to be influential to the weld formation, PA6 morphology and joint mechanical property. PA6 column became short and PA6 anchor gradually disappeared with the increase of S R . The PA6 particles were large and poorly connected with ABS matrix under S R 250. A large amount of PA6 particles were refined to a few microns or even hundreds of nanometers under S R 350, presenting spherical and rod-shaped morphologies. Meanwhile, their connection with ABS matrix became compact. Under S R 500, pores emerged in the nugget and gaps were generated along the nugget boundary. Lap-shear tensile tests showed that the fracture loads of the joints decreased with increased S R and two failure modes were observed. Elongated PA6 bands, deep holes and dimples were observed on the fracture surface of the nugget obtained under S R 350.