Macro-/micro-mechanical interlocking modification on the performance of hybrid friction stir spot welded aluminum/acrylonitrile butadiene styrene joints

Macro-/micro-mechanical interlocking enhancement of hybrid aluminum/acrylonitrile butadiene styrene (Al/ABS) joint is investigated via the use of joint modification approaches such as pre-fabricated threaded- and unthreaded-hole friction stir spot welding processes. The structure, tensile-shear failure load, and fracture behavior of the as-welded hybrid Al/ABS joints were investigated. Hybrid Al/ABS joint fabricated with threaded hole shows superior tensile-shear failure load due to the combined effects of compressive shearing-induced and threading-induced mechanical interlocks, and adhesion bonding mechanisms. The tensile-shear failure load of the threaded joint improved from 654 to 749 N as the tool rotational speed is increased from 710 to 1120 rpm. A rise in tool rotational speed improves the failure resistance of the hybrid Al/ABS joints (threaded and unthreaded) owing to the enhanced mechanical interlocking, bigger Al anchor/chip, and smaller interfacial gap between the re-solidified ABS and Al anchor. Threading and tool rotational speed have significant impacts on the fracture location and mode of the hybrid Al/ABS joint. The pre-fabricated threaded-hole friction stir spot welding process is thus recommended for the enhanced micro/macro-interlocking in hybrid Al/polymer joints.