Effect of recrystallization on intergranular fracture and corrosion of Al–Zn–Mg–Cu–Zr alloy

• The cracking preferentially propagated along the recrystallized grain boundaries.
• Higher density of continuous and coarser η precipitates distributed on the recrystallized grain boundaries.
• Fine and scattered η precipitates distributed on the un-recrystallized grain boundaries.
• Intergranular fracture and corrosion resistance increase with the decrease of recrystallization.

The influence of inhibiting recrystallization on intergranular fracture and corrosion behaviour of Al–Zn–Mg–Cu alloy has been investigated by using four independent localized corrosion tests (accelerated IGC, standard EXCO, DCB and U-bending tests), together with detailed microstructural characterization. Results indicated that the intergranular fracture and corrosion resistance of the peak-aged Al–Zn–Mg–Cu–Zr alloy could be substantially improved by inhibiting recrystallization through erbium and chromium additions. The cracking in ultra-high strength Al–Zn–Mg–Cu alloy preferentially propagated along the recrystallized grain boundaries with continuous and coarser grain boundary precipitates. The predominated fracture mode transformed from intergranular fracture to trans-granular fracture by inhibiting recrystallization.