Friction stir welding of single crystal aluminium

Friction stir welds were prepared in different orientations in an aluminium single crystal. The welds were quenched to preserve the microstructure surrounding the tool and then electron backscattered diffraction was used to reveal the generation of grain boundaries and the evolution of crystallography texture around the tool in each weld. The extent of both dynamic recrystallisation and conventional recrystallisation varied considerably as a function of weld orientation. As the base plate begins to interact with the deformation field surrounding the tool, regions of the single crystal rotate to new crystal orientations, producing new grain boundaries in the process. These refined grains develop a {112}〈110〉 texture closer to the tool. Large conventionally recrystallised grains sometimes form in the outer regions of the refined grain structure, but become ever more deformed as they approach the tool until they are indistinguishable from the surrounding material.