Influence of exfoliation corrosion on tensile properties of a high strength Al-Zn-Mg-Cu alloy

LIU Sheng-dan(刘胜胆)¹, LIAO Wen-bo(廖文博)^1,2, TANG Jian-guo(唐建国)¹, ZHANG Xin-ming(张新明)¹, LIU Xin-yu(刘心宇)^1,2

(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. school of Materials Science and Engineering, Guilin University of Electronic Science and Technology,
Guilin 541004, China)

Abstract:The influence of exfoliation corrosion on the tensile properties of a high strength Al-Zn-Mg-Cu alloy was investigated by ambient temperature tensile testing, optical microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). After exfoliation corrosion immersion, blisters and corrosion pits can be seen on the sheet surface, which lead to loss of materials and notches. A number of intergranular cracks are observed to initiate at the bottom of the corrosion-induced notches and propagate rapidly into the bulk materials during tensile. Consequently, exfoliation corrosion results in significant loss of strength and brittle fracture. EBSD results show that the crack propagation path is primarily along the grain boundaries with misorientation of ~45^o, and coincidence site lattice (CSL) boundaries are slightly more resistant to crack.

Key words:exfoliation; tensile properties; fracture; grain boundaries; Al-Zn-Mg-Cu alloy