Friction filler welding

A method of joining a first workpiece and a second workpiece by friction filling welding, the first workpiece having a first end face through which a firs:

• longitudinal axis extends and the second workpiece having a second end face through which a second longitudinal axis extends, the method comprising:
• arranging the first and second workpieces such that their respective first and second end faces are positioned adjacent each other and separated by a gap;
• positioning an intermediate member as a filler of the gap between the first and second end faces, each of the first and second end faces defining a cross sectional area, and the intermediate member having an intermediate longitudinal axis that intersects transversely the first and second longitudinal axes and an exterior surface that covers the crass sectional areas of the first and second end faces;
• imparting rotational motion about the intermediate longitudinal axis of or vibratory motion to the intermediate member and pressing the first and second workpieces toward each other in directions along their respective first and second longitudinal axes to produce friction pressure between the exterior surface of the intermediate member and the first and second end faces of the respective first and second workpieces;
• and
• upset bonding the first and second workpieces to the intermediate member on bringing the rotational motion or the vibratory motion of the intermediate member to a halt.