We have proposed a novel joining process, Friction Lap Joining (FLJ) to join metallic material sheet directly to polymer sheet and have investigated mechanical and metallurgical properties of these dissimilar joints. It was described in this paper that joining mechanism was discussed with the evaluation of TEM microstructure at the joint interface between A2017 aluminum alloy and 2 kinds of polymer, ethylene-acrylic acid copolymer (EAA),and high density polyethylene (PE). EAA sheet was easily joined to an as-received aluminum alloy sheet by FLJ, because EAA had a polar functional group, COOH. On the contrary, PE was not able to be joined to an as-received aluminum alloy, because PE had no polar functional group. However, anodizing of aluminum alloy was effective to join these materials by the assistance of the anchor effect.

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Tensile stress-strain properties of Al alloy 6061-T6 (AA6061-T6) and its butt welds produced by the friction stir welding (FSW) process were characterized in two different loading orientations. AA6061-T6 FS welds were made under three sets of welding conditions. Micro-hardness tests were performed to investigate microstructural evolution during the FSW process. Flat tensile specimens were machined normal and parallel to the weld line. Transvers and longitudinal tensile tests were run on the base material (AA6061-T6) anditsFSweldsinanInstron testing machine. The strength and ductility (or fracture strain) of the FS welds observed in the transverse orientation were substantially less than those in the longitudinal orientation. Constitutive modeling of uniaxial tensile stressstrain behavior in both orientations was presented using a rateindependent Ludwik equation. In addition,microstructures of the base material and its FS welds were examined with optical and transmission electron microscopy to discuss the decrease in the flow stress level and the increase in the strain hardening rate of the FS welds.

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