Correlation of dynamic torsional properties with adiabatic shear banding behavior in ballistically impacted aluminum-lithium alloys

The present study is concerned with a correlation between dynamic deformation properties obtained from the dynamic Kolsky bar test with the adiabatic shear banding behavior developed in Al-Li alloys upon ballistic impact, and then with the ballistic performance. The selected materials were a 2090 Al-Li alloy, a WELDALITE 049 alloy, and a 7039 Al alloy, to allow a comparative study of different strengths and microstructures. After the ballistic impact testing, the amount and the distribution of adiabatic shear bands were examined using optical and scanning electron microscopes. In the front side of the impacted area, many thin delaminated sheets and a large amount of fragmentation were observed in the 2090 alloy and the WELDALITE alloy, respectively. Near the impacted region, a large amount of plastic flow also existed, and adiabatic shear bands were hardly observed in the 2090 and the WELDALITE alloys, whereas they easily formed in the 7039 alloy. Since adiabatic shear bands usually deteriorate the impact resistance of target materials, the ballistic performance of each alloy was discussed by comparing the adiabatic shear banding behavior with microstructure, strength level, and dynamic torsional properties.