Selected Microstructural Phenomena in FSW Joints

The article is a literature review on selected phenomena leading to microstructural changes in material welded using the friction stir welding (FSW) method. Particular attention was paid to the phenomena of grains recrystallization, as well as dissolution and reprecipitation of second phase particles, resulting from temperature changes during FSW. Temperature transformations in different zones of the FSW joints were characterized. The role of base material phase transformation in the formation of new particles is discussed. In the tested aluminum alloys and stainless steels, this process was particularly intensified in the heat affected zone (HAZ). In areas subjected to high temperature and significant plastic deformation (nugget zone and thermomechanically affected zone), this phenomenon did not occur or was characterized by small intensity. It was indicated that the phenomenon of particle formation clearly affects the strength parameters of the joint.