J. Teimournezhad - School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran

The aim of this investigation was to understand the flow of material in the welded joint that is produced by a non-threaded pin (with four flats on the pin-tip) in copper plates. Careful examination and the findings of this study indicate that four distinguishable zones (surface layer, surface material, in-situ material and thermo-mechanically affected zone on the retreating side) are developed in the stir zone during the welding process. In each rotation of tool, all these zones are merged and one new layer of weld is produced.

Friction stir welding; Copper; Metallography; Material flow