Coupling effect of electrophoretic deposition and solid-phase joining on CNTs/Mg multi-material joint.

The carbon nanotubes (CNTs) mixing inside a joint between two fastened parts of the material is the key to realize balance of strength and elongation. The electrophoretic deposition was innovatively applied to friction stir butt welding Mg plates to form CNTs/Mg joints. The results showed that the CNTs was involved to the adjacency of the butt weld mixing zone (BWMZ) by a concave shoulder and will be brought into the BWMZ through the forward force of the conical probe. Two pieces of plates deposited with CNTs were jointed without defects at various welding speeds through the advanced solid-phase joining techniques (electrophoretic deposition assisted with friction stir butt welding). When compared to the CNTs/Mg joint, the grains of the joint without CNTs were coarser and more aeolotropic. CNTs can generate Orowan strengthening due to confinement effect of dislocations slip, and CNTs with a high specific surface area also can serve as contact interface, leading to resistance at for localized plastic deformation, and with the increase of the total grain boundary, the strengthening effect becomes predominant. When bonding between matrix and CNTs was tight, the hard CNTs were difficultly pulled out from joint and then breaking energy will be absorbed and help to hinder crack propagation and expansion, which results in decent elongation. Consequently, CNTs mixed joint exhibits more balanced tensile properties compared to traditional joints. [ABSTRACT FROM AUTHOR]