Study On The Damage Behavior Of The 7050 Aluminum Alloy Under High Velocity Impact Conditions

The deformed behaviors of two types heat treated 7050 Al alloy under high velocity impact were investigated in this paper. High velocity impact experiments were carried on a two-stage gas gun using 5 mm GCr15 steel ball with a spped of 1.5~3.5 km/s. The impact cratering process in 7050 Al alloy target under different impact velocities was analyzed, and the macroscopic damaged behaviors of the targets were obtained. The adiabatic shear bands and deform microstructures adjacent to the crater under high velocity impact were characterized by OM, SEM and TEM, while the mechanical property of the deforme microstructure near the crater was measured by tension tests.The investigated results show that the cratering process of the aged 7050 Al alloy under high velocity impact was different from the solution treated Al alloy. At almost same impact velocity, larger crater volume formed in the solution treated Al alloy than that formed in aged Al alloy was obtained because of low yield strength and high elongation. Yield strength of the materials was the main factor to influence the macroscopic damaged behaviors of the targets. High yield strength of the targets led to the crater volume decreasing, then the impact resistance of the materials improvement.Adiabatic shear bands and cracks were the main damaged modes of the materials near the crater under high velocity impact. With impact velocity increasing, the quantity of the cracks near the crater increased, and the quantity of the adiabatic shear bands was associated with targets. With impact velocity imcreasing, the quantity of the adiabatic shear bands formed in the solution treated 7050 Al alloy increased, while the quantity of the adiabatic shear bands in the aged 7050 Al alloy decreased. The isolated adiabatic shear bands were main feature in the aged 7050 Al alloy, and the net-like adiabatic shear bands were formed in the solution treated 7050 Al alloy.High velocity impact led to the materials near the crater suffered the severe plastic deformation. Based on the difference of the deformed microstructure adjacent to the crater, threee deformed zone could be classified: severe deformed zone, shear localized zone and strain hardened zone. With the impact velocity increasing, every deformed zone was broadening. Compared with the aged 7050 Al alloy, the wider deformed zones in the solution treated 7050 Al alloy were obtained because of the severe plastic deformation. The measured mechanical properties show that with impact velocity increasing, the yield and tension strength of the deformed microstructure were improved, and the corresponding elongation decreased. Compared with the aged 7050 Al alloy, the increment of the yield and tension strength of the deformed microstructure near the crater in the solution treated 7050 Al alloy was lager, while the decrement of the corresponding elongation was also larger.