The role of rotation speed on intermetallic compounds formation and mechanical behavior of friction stir welded brass/aluminum 1050 couple

► Intermetallics are formed during welding in the stir zone and at the interface. ► CuAl2, Cu9Al4 and CuZn are dominant intermetallic compounds. ► The narrow interfacial intermetallic layer enhances the strength of the weld. ► High rotation speed is accompanied by thickening of interfacial intermetallic layer. ► Extreme thickening of the intermetallic layer lowers the strength of the weld.