TEXTURE DEVELOPMENT IN ALUMINUM FRICTION STIR WELDS

摘要

This study reveals the development of texture and microstructure that occurs during friction stir welding of two aluminum alloys. Friction stir welds of single crystal aluminum and 2195 aluminum were investigated using a stop-action technique, where the microstructure surrounding the tool was preserved by immediately quenching the weld end upon completion. Plan view sections of these weld terminations reveal that slight variations in the crystallographic orientation within the base material have different susceptibilities to the shear deformation produced by the rotating tool. Similarly, the misorientations generated during subgrain development can also induce variations in the lattice rotation rate. The divergent orientations that develop can have different susceptibilities to both rotation and grain subdivision. Lattice rotations continue until achieving a readily-sheared orientation, after which no further rotation is observed. The final texture that develops near the tool corresponds to the B and B components of the simple shear texture. In the 2195 alloy, the deposited weld also exhibits a simple shear texture, but it varies with a periodicity of the tool advance per revolution between a pure B/B component and a mixture of the B/B and C components. Thus, the development of textures ahead of the tool can be correlated directly to the increasing temperature and shear deformation of those regions, while the periodic texture variations of the deposited weld indicate a systematically varying component in the friction stir welding process.