Analysis of microstructure and high-temperature tensile properties of 2060 Al-Li alloy strengthened by laser shock peening

Highlights: • The elevated mechanical properties of high strength of 2060 Al-Li alloy were considerably influenced by LSP. • The variation of microstructure and residual stress along the depth of LSPed 2060 Al-Li alloy were studied by TEM and XRD. • The primary mechanism of LSP for improving high temperature tensile properties was established. -- Abstract: Laser shock peening (LSP) is a promising surface technique effective to improve mechanical properties by laser modification. In this study, LSP was used to strengthen the surface of a new generation of light-weight Al-Li alloy (i.e., 2060 alloy). High-density dislocations were formed in the vicinity of precipitate phase. A residual stress of compressive state was detected on the surface. According to the tensile tests conducted at various temperatures, the strength of the alloy was improved with LSP, but simultaneously, the ductility was reduced. The fractograph on the tensile sample subjected to LSP, or as received (free of the modification by laser), was characterized by a quasi-cleavage when the tensile temperature was below 200 °C, whereas ductile fracture was considered to be a determining factor at the temperature of tension above 300 °C. Dislocation strengthening was analyzed as a primary mechanism of LSP for improving high-temperature tensile properties. Namely, this improvement was attributed to the existence of a lot of dislocations near precipitates.