Microstructure evolution of 2195 Al-Li alloy friction stir welded joint and enhancing performance by laser shock peening

To investigate the microstructure and mechanical properties of friction stir welding (FSW) joints of 2195 aluminum-lithium alloy and attempt to improve them, 6.5 mm thick 2195-T8 aluminum-lithium alloy test plates were welded using different parameters. The microstructure evolution of different zones of the joints was investigated using OM, EBSD, TEM and other analytical techniques. The mechanical properties including microhardness and tensile properties of the joints were tested and digital image correlation (DIC) was applied. The results indicate that FSW of 2195-T8 aluminum-lithium alloy can reliably produce well-formed joints within the tested parameter range, with a strength coefficient of 70% and a fracture elongation of 7%. T1 and θ' completely dissolved in the weld nugget zone while β'/δ' was formed. Strain concentration occurred in the weld nugget and shoulder affected zones during tensile testing. After double-sided laser shock peening (LSP), the yield strength of the joint increased by 51 MPa, and the fracture path shifted from the weld nugget zone to the outer side of the thermal-mechanical affected zone. The new fracture location corresponded to the region of lowest hardness as determined by hardness testing.