Effect of shoulder size on the temperature rise and the material deformation in friction stir welding

A fully coupled thermo-mechanical model is adopted to study the effect of shoulder size on the temperature distributions and the material deformations in friction stir welding. Numerical results indicate that the maximum temperature can be increased with the increase of the shoulder diameter. The stirring zone can be enlarged by the increase of the shoulder size. With consideration of the recrystallization formula, it is found that the temperature variation is the main factor for controlling the grain growth near the welding line. But, when the strain and the strain rate become smaller near the border of the stirring zone, the recrystallization process is dominated by the material deformations instead of the temperature rise.