Effect of Annealing on the Microstructure, Mechanical Properties, and Intergranular Corrosion of a Novel Al–Mg–Zn Alloy

Abstract

The effect of annealing on the mechanical properties, intergranular corrosion (IGC) properties, and microstructure of Al–Mg–Zn alloys is studied. The results show that with the increase of annealing temperature, the strength of the alloy decreases, the elongation increases, and the corrosion resistance firstly increases and then decreases. The alloy exhibits a high corrosion resistance and good mechanical properties when the annealing treatment is 270 °C for 2 h. Meanwhile, the IGC mass loss value is less than 15 mg cm−2. In addition, the ultimate tensile strength, yield strength, and elongation are 416, 250 MPa, and 16.0%, respectively. The T‐Mg32(Al, Zn)49 phases are directly precipitated when annealing at 270 °C for 2 h. After sensitization, T phase gradually grows and coarsens. When the alloy is annealing at 400 °C for 2 h, a part of T phase gradually dissolves in the Al matrix. After sensitization, the Mg atoms with higher supersaturation gradually diffuse to grain boundary by bulk diffusion due to the low dislocation density and form a thin precipitate film, which deteriorates the corrosion resistance of the alloy. The details of corrosion mechanism analysis are as follows.