Abstract: Al5A06 sheets by large cold plastic deformation usually have high strength but low plasticity, i.e. weak strength-plasticity matching, which may lead to their poor fatigue property. In this study, annealing treatments are applied on cold rotary forged Al5A06 sheets to regulate strength-plasticity matching and improve fatigue properties. The microstructures, tensile mechanical properties and fatigue properties under different annealing parameters were analyzed. The abnormal grain growth mechanism of cold rotary forged Al5A06 sheets during 300 °C annealing treatment was investigated, and the fatigue failure mechanism of Al5A06 sheets with different annealing temperatures was also investigated. The abnormal grain growth during 300 °C annealing treatment is mainly due to the asynchronous recrystallization behavior with low recrystallization driving force, which leads to the early recrystallized regions directly absorbing adjacent grains along 〈134〉 crystal direction. The cold rotary forged Al5A06 sheets after 250 °C-2 h annealing treatment exhibit the best fatigue property, which is mainly because the optimum strength-plasticity matching brings about coordinate plastic deformation throughout most grains, and the effective dislocation movement between adjacent grains can delay the appearance of strain localization and accommodate continuous fatigue cyclic loading.

Key words: Al5A06 sheets, Cold rotary forging, Annealing treatment, Strength-plasticity matching, Fatigue property