Microstructural properties of a dissimilar friction stir welded thick aluminum aa6082-t6 and aa7075-t6 alloy

Abstract

Friction stir welding is a severe plastic deformation process. This solid state welding procedure has recently received a general acceptance in the aerospace industry for joining difficult to weld aluminum alloy using the conventional method. A 10mm thick AA6082 and AA7075 in tempered form (T6) were friction stir welded in butt configuration as against the previous research on 4mm, 6mm and 8mm thicknesses respectively. The response of the stir zone (SZ) microstructure to processing parameters was evaluated using optical microscope (OM), Stereo microscope (SM) and scanning electron microscope (SEM) respectively. The magnitude forge force (kN) at the tool shoulder directly affect the flow of the extruded materials through the tool probe. The distribution of thermal energy, dissolution, precipitation and re-precipitation of solute influences the materials flow and properties evolution. Hence, equiaxed grain structures observed were due to the dynamic recrystallization mechanism at the weld nugget. Some microstructure imperfection were observed at the weld nugget when AA6082 aluminum plates were clamped on the retreating side to the backing plate. However, the material flow and mixing was not sufficient to establish good bonding and quality welds due to deviation in the positioning of the aluminum plates.