A NEW TYPE OF PLUG-IN FRICTION-STIR LAP WELDING BASED ON THE 6061-T6 ALUMINUM ALLOY

In this study a new type of plug-in friction -stir lap welding (PFSLW) is proposed to prepare welded joints based on 4 -mm -thick 6061-T6 aluminum alloy sheet. The differences in the cross-sectional morphology, microstructure, cross-sectional hardness and shear properties between the PFSLW joint and the normal friction -stir lap -welding (FSLW) joint are discussed. The results show that the cross-sectional morphology of the PFSLW joint has undergone changes. The PFSLW joint has a mechanical interlocking structure on the advancing side that is beneficial to the connection strength of the joint. The grain structure differs at the boundary between the thermo-mechanically affected zone (TMAZ) and the heat -affected zone (HAZ), and the PFSLW joints show a more pronounced bending deformation of the grain organization near the boundary. The microhardness of PFSLW joints was increased in the TMAZ and HAZ areas, and the lowest hardness is further away from the center of the weld. The failure load of the PFSLW joint has been improved, the microcracks part of the PFSLW joint has a ridge -like structure. In addition, the actual welding width of PFSLW joints was improved.