Study on intermediate annealing process of thermal mechanical treatment of 7185 alloy with two stage deformation

Abstract

This study investigated the effect of intermediate annealing (IA) during a special thermo-mechanical treatment on the microstructure and properties of 7185 Al alloy. The results show that after IA, many sub-structures are formed in the alloy and many particles are precipitated. The particle size increases and the width of the dislocation wall becomes narrower with increasing IA time and temperature. After the second stage of deformation, the dislocations are ordered again and generate micro shear bands (MSBs). The final T6 treated alloy under IA2 process (holding time for 40 min at 400 °C) has good plasticity and corrosion resistance. The tensile strength is 523 MPa, the yield strength is 458 MPa, the elongation is 17.6%, the depth of intergranular corrosion layer is 15.6 μm, and the corrosion grade after 6 and 12 h exfoliation corrosion is N, PC.

Keywords

• Thermo-mechanical treatment
• Al–Zn–Mg–Cu alloys
• Microstructure
• Mechanical properties
• Corrosion resistance