Study On The Damage Behaviors Of Aluminum Alloy Under The Hypervelocity Impact

In the paper, the damage behaviors of 2A12 aluminum alloy and 7A09 aluminum alloy under the hypervelocity impact was studied. The test parameters of the hypervelocity impact test were determined using the numerical simulation by Ansys Auto DYN software. The mechanical damage and mechanical properties of aluminum alloy after hypervelocity impacting were studied by the optical microscope, the posture microscope and laser range finder. The hypervelocity impact damage and tensile fracture behavior of aluminum alloy were studid by X ray diffraction, transmission electron microscope and scanning electron microscope.The investigated results show that the aluminum alloy incident projectile whose diameter was 4mm impacted and punched a hole on the aluminum alloy front panel whose thickness was 2mm as the speed of 3~4km/s, then the debris cloud impacted the parallel arrangement aluminum alloy specimens whose thickness was 5mm. The distance between the front plate and specimens was 100 mm. The aluminum alloy specimens with different size of craters and different distribution were got to ensure that the perforation ans the surface layer spallation does not occur.After hypervelocity impacting, the tensile fracture position of the damaged specimens were related to the depth, the diameter and the location of the craters. As the ratio of the impact crater depth to the original specimen thickness and the ratio of the impact crater diameter to the original specimen width was increased, the extensibility of the damaged aluminum alloy specimen was reduced, and the tensile strength and the yield strength didn’t have the significant change. The impact crater was the crack source of tensile fracture of aluminum alloy. There are a lot of tough and torn edges in tensile fracture, which is a ductile fracture.At the same time, a lot of high density of helical dislocations and slip lines were obversed near the craters on the 2A12 alloy, the high density of helical dislocations and entangled dislocation were obversed near the craters on the 7A09 alloy. It indicated that the decrease of the aluminum alloy plasticity caused by the process hardening under the hypervecity impacting. There were two contradictory factors which were the process hardening and the reduction of the bearing area led to the little change of the strength of the aluminum alloy.