Local strain analysis under quasi-static tensile loading in Al/steel dissimilar friction stir weld by a digital image correlation method

A6061-T6 aluminum alloy plate was butt welded to type 304 stainless steel plate by a friction stir welding (FSW) technique to fabricate a dissimilar weld. Subsequently, digital image correlation (DIC) analysis was performed on the top, bottom, and side surfaces of dissimilar weld to investigate the local deformation behavior near the joint interface under a tensile loading condition. The normal strain in the loading direction concentrated near the interface on both top and bottom surfaces. The positions of the strain-concentrated areas were different on both sides, around 9 mm away from the interface on the top surface and 6 mm away on the bottom surface, which could be attributed to the local softening developed during the FSW process. The local stress–strain curves were obtained in the weld zone. The largest strain was obtained at thermo-mechanically affected zone (TMAZ), and the local 0.2% proof stress was estimated about 120 MPa, while that of base metal was 287 MPa.