Effect of Friction Stir Processing on the Microstructural and Mechanical Properties of St-37GMA-Weldmetal

In this research, friction stir processing (FSP) was carried out to modify the microstructure and mechanical properties of gas metal arc (GMA) welded St37 base metal. Microstructural studies revealed that with applying FSP on the GMA-weld metalsignificant microstructural modification occurred and as-cast coarsegrains of weld metal modify to the fine grain, i.e. a reduction of weld metal grain size about 50% occur after FSP. This variation of grain sizes could be contributed to the recrystallization inFS-processed zone, i.e. high temperature accompany with significant deformation during FSP resulted in recrystallization and formation of fire grains in weld metal. Evaluation of mechanical properties indicated that applying FSP on the GMA-weld metal caused increasing ductility and uniform hardness profile of modified specimens that was in harmony with microstructural results.