Microstructure and mechanical properties of 2195-T6 Al–Li alloy joint prepared by friction stir welding

Friction stir welding was carried out on 2 mm thick 2195-T6 Al-Li alloy sheets. Effect of welding speed on microstructures and mechanical properties of the joint was investigated by OM, SEM, EBSD and other analytical techniques. The results show that at the rotational speed of 800 r/min and the welding speeds of 120-210 mm/min, the grains in the nugget zone are all relatively smaller, with theaverage grain size is above 1 μm. With an increase of welding speed, the ratio of high angle grain boundaries is increased. 110<110> and 011<100> Goss texture are disappear. The lowest hardness are found at the heat affected zone of the retreating side. Both tensile strength and elongation reach their maximum value at the welding speed of 180 mm/min, with a maximum tensile strength of 467 MPa, which is about 86.3% of the base metal, while the maximum elongation is about 5.0 %. The fracture mode is ductile fracture, while the fracture also shows partial brittle fracture characteristic.