Microstructure, Mechanical Properties, and Corrosion Behavior of Al-4.0Cu-1.1Li-0.5Mg-xAg Alloys

Abstract

The influence of various Ag contents on the microstructure, mechanical properties, and corrosion behavior of extruded Al-4.0Cu-1.1Li-0.4Mg-xAg-0.2Mn-0.2Zr (x = 0.4 and 0.9, wt.%) alloys was investigated. The alloy with 0.9 Ag content contains higher number density of slender T1 (Al2 CuLi) precipitates along with some θ’ (Al2 Cu) phases in the matrix than the alloy with 0.4 Ag content, which is associated with a more rapid hardening response and higher mechanical properties and corrosion resistance, particularly for aging at 130◦ C. When aging at high temperatures (above 160◦ C), the increase of Ag content mitigates hardness loss by preventing the T1 precipitates from coarsening, and makes the alloy decorate more coarse precipitates at grain boundaries, which leads to the fracture morphology mainly occupied by intergranular fracture. Furthermore, due to the simultaneous promotion of T1 precipitates at grain boundaries and in grain interiors, the 0.9 Agcontaining Al-Cu-Li-Mg-Ag alloy has almost no improvement in corrosion resistance.