By means of microstructure observation, hardness test and torsion strength test, some characteristics of the friction welded joint undergoing an external electric field have been studied quantitatively. The recrystallization grain size in the weld metal zone (WMZ) decreases when the external electric field is applied. The equiaxed grains in the dynamic recrystallization zone (DRZ) increase and the equiaxed characteristic of recrystallization grains in the DRZ is enhanced. The microstructure of the welded joint along the axial direction becomes more homogeneous. When the same friction welding parameters are applied, the electric field causes an increase in the width of the DRZ. Moreover, the external electric field effect leads to the hardness of the welded joint increasing, and also homogenizes the hardness distribution along the radial and axial directions. In addition, the average torsion ductility of the weld metal increases in the case of applying the external electric field. (C) 2003 Kluwer Academic Publishers.