Abstract:The influence of Li addition on mechanical property and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy was investigated by tensile test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results show that the tensile strength can be significantly improved with the slightly decreased ductility and the form of fracture morphology is converted from ductile fracture into ductile/brittle mixed fracture by adding 1.0% Li. Besides, the peak aging time at 185 °C is delayed from 12 to 24 h and the main precipitation phase S''''(Al₂CuMg) is converted into S'''' (Al₂CuMg)+δ''''(Al₃Li), while the formation of S''''(Al₂CuMg) is delayed.

Key words: aluminum alloy; Al-3.5Cu-1.5Mg alloy; Li; aging behavior; mechanical properties