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Mechanical properties of 2124 aluminum alloy thick plate in short-transverse direction were investigated when ageing at 170-180℃ for different time by room temperature tensile test.The microstructure morphology of alloy after different ageing processes was studied by TEM and SEM.The results show that the suitable ageing process of 2124 aluminum alloy plates is 175℃ for 10h.Yield strength, tensile strength and elongation are 372,422MPa and 2.9%, respectively.The main precipit-ation is S' phase, and also a small quantity of GPB zone and coarse T phase exist at this moment.Ageing temperature is the main factor affecting the density and size of the alloy precipitation.The higher the ageing temperature is, the quicker the rising of strength, the shorter time to reach the maximum strength.The increasing strength difference between the matrix and grain boundary is the main cause for the decrease of the elongation.

The intergranular corrosion and exfoliation corrosion properties of 7475-T7351 aluminum alloy plate for aviation were investigated, and the corrosion behaviors of the alloy were analyzed by metallographic analysis(MA) and transmission electron microscope(TEM). The results show that no obvious intergranular corrosion is observed, but exfoliation corrosion grade of 7475-T7351 aluminum alloy increases from EA on surface to EC in the core. The exfoliation corrosion of 7475 alloy plate is mainly because of the typical lamellar structure, and the pathway formed by galvanic corrosion on grain boundary. The expansion of grain boundary corrosion product volume produces the wedging force,makes intergranular corrosion grow along the direction in parallel with the surface,and then gradually evolves into exfoliation corrosion. The degree of recrystallization decreases gradually from the surface to center, and the grain length-to-width radio increases, which inclines to exfoliation corrosion and leads to the exfoliation corrosion grade increasing from surface to center.

Microstructure evolution during hot deformation of a new Al-Zn-Mg-Cu alloy was investigated by Gleeble-1500D thermal-mechanical simulator at 300-450℃ and strain rate of 0.001-10s-1.The microstructure features at different hot deformation conditions were analyzed with optical microscope (OM) and transmission electron microscope (TEM).The results show that the dislocation density decreases and the subgrain sizes increase with the increase of deformation temperature and the decrease of the strain rate;the main softening mechanism of the alloy is dynamic recovery and dynamic recrystallization.Only dynamic recovery occurs when the temperature is 300-400℃.Dynamic recrystallization occurs when the strain rate is 0.001-10s-1 at 450℃.The nucleation mechanism is grain boundary bowing,subgrain growing and subgrain incorporation during dynamic recrystallization.