Microstructure and Mechanical Property Evolution of Robotic Friction Stir-Welded Al–Li Alloys

2198 aluminum–lithium alloy was friction stir-welded with a KUKA Robot integrated compact stir-welding head rotation speed of 800 rpm at different welding speeds. The real-time tool force in the three directions Fx, Fy and Fz measured load sensor. Mechanical properties microstructure evolution were investigated systematically. results showed that increased from 3.2 kN to 8.5 as 50 mm/min 500 mm/min. Ultimate tensile strength 383 MPa, 88% base metal, obtained when 100 nugget zone consisted refined grains an average size 4 μm. TEM investigation demonstrates T1 precipitation predominated metal disappeared zone, small amount δ’ retained. W-shape hardness profile all weldments higher lead value.