Microstructures And Mechanical Properties Of 2A12 Aluminum Alloy After Age Forming

Age forming of 2A12 aluminum alloy was studied through experiments and microstructure observation with OM, XRD, SEM and TEM. This paper mainly studied four aspects:(1) The difference in microstructure and mechanical properties of 2A12 aluminum alloy after age forming and artificial aging; (2) The evolution law of springback rate, microstructures and mechanical properties of 2A12 aluminum alloy after age forming with prebending radius; (3) The evolution law of springback rate, microstructures and mechanical properties of 2A12 aluminum alloy after age forming under different forming temperature; (4) The evolution law of springback rate, microstructures and mechanical properties of 2A12 aluminum alloy after age forming with different holding time. The results were as follows.1. The grain of 2A12 aluminum alloy after age forming was further squashed and lengthened than that after artificial aging. Because of infliction of elastic load, the precipitate after age forming was long strip shape and presented orientation while that after artificial aging was punctiform and well distributed. The dislocation shapes of 2A12 aluminum alloy between age forming and artificial aging were also different. The dislocation shape of 2A12 aluminum alloy after age forming was long and straight dislocation, while that after artificial aging was ring dislocation or helical dislocation. After age forming, the tensile strength of 2A12 alloy decreased less than 6%. Meanwhile, the fracture toughness of 2A12 alloy after age forming was slightly less than that after artificial aging, and the fatigue crack growth rate was relatively faster.2. The springback rate increased with the increasing of prebending radius. Forming temperature and holding time were important factors affecting size and quantity of the precipitate, while the prebending radius had no significant effect on size and quantity of the precipitate. Meanwhile, the change of prebending radius had little or no effect on mechanical properties of 2A12 aluminum alloy after age forming.3. The springback rate reduced with the increase of forming temperature. Because of the temperature increment, both size and quantity of the precipitate after age forming increased and average interparticle spacing of the precipitate also increased. When holding time was 6h, the forming temperature gradually increased to 190℃, then the strength of 2A12 aluminum alloy after age forming gradually increased, but the specific elongation gradually reduced; simultaneously the fracture toughness generally reduced and the fatigue crack growth rate increased in the whole.4. The springback rate decreased with the extending of holding time. In the early stage, the descent velocity of springback rate was fast. Later, the descent velocity of springback rate became slow and gradually stabilized. With the prolongation of holding time, the size of the precipitate became bigger and the quantity of the precipitate increased, and the precipitate transformed from transition phase S to equilibrium phase S; the strength of 2A12 aluminum alloy after age forming gradually increased to peak value and then decreased, but the specific elongation showed downtrend all the time; meanwhile, the fracture toughness was on the decline, and the fatigue crack growth rate gradually increased.