Effect of Solution Process on Microstructure and Damage Tolerance Properties of 7075 Aluminum Alloy Sheet

Annealed and work-hardened 7075 aluminum alloy sheets were soluted at different temperatures (466, 479 ℃) for different times (5, 55 min) in a hot air circulation furnace (heating rate of 5 ℃ · min⁻¹). The work-hardened 7075 aluminum alloy sheet was soluted at 479 ℃ for 2–3 min in a hot air circulation furnace (heating rate of 151–227 ℃ · min⁻¹). The sheets after solution treatment were aged at 121 ℃ for 24 h. The effect of solution treatment process on the microstructure and damage tolerance properties of aluminum alloy sheet was studied. The results show that when the holding time was prolonged or the solution temperature was increased in the hot air circulation furnace, the aggregation behavior of the second phase particles in the annealed sheet was improved, and the fracture toughness was improved; the second phase particles in the work-hardened sheet were small in size and evenly distributed, and the fracture toughness did not change significantly. Due to the high heating rate and short holding time in the air cushion furnace, the large-sized second phases in the work-hardened sheet could not be fully redissolved and showed irregular morphology, and the fracture toughness decreased compared with that in the hot air circulation furnace. Isolated or aggregated large-sized second phases were the key factors affecting the damage tolerance properties.