Influence of thermal exposure on the microstructure evolution and mechanical behaviors of an Al-Cu-Li alloy

•The T85 treated Al-Cu-Li alloy was systematically investigated under thermal exposure at 100–300 °C for up to 1000 h.•The evolution of precipitation characteristics during thermal exposure was revealed.•Fracture toughness was greatly affected by the morphology and distribution of grain boundary precipitates.•The qualitative relationship between mechanical properties and multiscale microstructure was established.