Investigation of the microstructural, mechanical, and thermal evolution of dissimilar aluminium alloys during friction stir welding

Abstract

This work deals with the joining of 6 mm thick dissimilar aluminium plates (AA5083-H111 and AA6082-T6) using a friction stir welding method and by varying the process parameters. Test experiments were performed to identify the influence of process parameters on the joint efficiency of the weldments. The process parameters such as tool rotation speed and tool pin profile were varied; whereas, tool travel speed, tilt angle, and axial force were kept constant for all weldments. Microstructure evaluation was carried out using light optical and scanning electron microscopes, which exposed the grain refinement in the nugget zone (NZ) and thermo-mechanical affected zone (TMAZ). Mechanical property tests for tensile strength, hardness, and bending were performed to understand the influence of the parameters over the weldments. Heat development between the tool shoulder and workpiece was analyzed by calculating the heat flow and heat flux. The thermal diffusivity of AA5083-H111 and AA6082-T6 were calculated to understand the influence of heat distribution in the joint efficiency of the weldments. It is inferred from the current study that the threaded cylinder tool at a rotational speed of 900 rpm achieved the highest tensile strength, hardness, and bend strength over the combination of other parameters.

Traverse and longitudinal analysis of AA5083/AA6082 dissimilar joint

“…In both the traverse and longitudinal samples, the grains exhibit a fragmented appearance, resembling tiny shards of glass. This appearance is a well-known consequence of recrystallization in friction stir welded samples [29,30]. Notably, the AA6082 material displayed this characteristic to a greater extent, while AA5083 exhibited a distinct feature whereby some grains appeared to merge, as observed in the SME samples shown in figure 4(c).…”

“…As for the failure locations in the longitudinal samples, they are likely influenced by the observations made in the longitudinal micrographs. Certain sections of the samples were found to still have large grains, or it could be attributed to the effect of abnormal grain growth or migrating grain boundaries of the AA5083 material [28][29][30].…”