Effect of deformation temperature on mechanical properties and microstructure of 7075 aluminum alloys processed by integrated hot forging

Abstract

Integrated hot forging process (solid solution → forging → aging) of aluminum alloy exhibits a distinct advantage in terms of shortening the processing time and enhancing the mechanical properties. Based on this, solution-hot deformation and then aging experiments, as well as OM, SEM and EBSD tests were carried out to investigate the effect of deformation temperatures (410°C, 440°C, 470°C, 490°C) on the microstructure and mechanical properties of aged 7075 aluminum alloy. The results indicate that the average strength and hardness of the aged alloy samples exhibit a gradual increase as the deformation temperature rises. When subjected to a deformation temperature of 490°C, the alloy displays optimal tensile properties, with an ultimate tensile strength of 536 MPa and a yield strength of 480 MPa. Simultaneously, the increase of deformation temperature causes a reduction of dislocation density within the alloy, enhances the degree of recrystallization, and promotes more uniform grain size and tendency to sphericalization. Especially, with a lower deformation temperature, the primary precipitates precipitated early after hot deformation and then grow and coarsen during the subsequent aging. This results in a lower volume fraction of nanoscale precipitates during subsequent aging, which is the primary factor leading to the decrease of mechanical properties for the alloys with the reduction in deformation temperature.