Evolution of Mechanisms of Plastic Strain Responsible for Structure Formation in Near-Weld Zone Under Friction Stir Welding

Abstract

The microstructure of welded joints obtained by friction stir welding (FSW) of structural steels and aluminum, copper and titanium alloys is studied. It is shown that the traditionally formed heat-affected zone is accompanied in the near-weld zone of FSW joints by a zone affected by thermal deformation (TDAZ) lying between the nugget and the HAZ. Two groups of alloys differing in the mechanism of plastic strain under FSW and affecting the formation of TDAZ and HAZ are distinguished.