Microstructural and Mechanical Characterization of Friction Stir-Assisted Lap Joining of Mg Alloy

The complexity of welding Mg alloys using conventional welding can be overcome by using friction stir welding (FSW), by virtue of its solid state joining process. In the present study, two Mg alloy plates were welded using the FSW technique. FESEM image shows that both the plates were joined effectively without any internal defects such as porosity, voids, and tunnelling. EDX reveals that there was the formation of an oxide layer on the stir zone (SZ) which helps to increase the hardness value at the SZ and was obtained to be greater than the base metal. An optical microscope (OM) reveals the fine and equiaxed grain microstructure in the stir zone because of dynamic recrystallization. Coarser and elongated grains are present in TMAZ and HAZ. Furthermore, micro-hardness obtained at stir zone was more than the base metal. The obtained result shows that FSW of Mg alloy can be a promising method to produce lap joints with improved microstructure and mechanical properties. Moreover, FSW can be employed to join dissimilar materials. FSW is adapted in additive manufacturing process to build parts (as functionally graded materials) layer by layer of dissimilar materials.