Ballistic Evaluation of Aluminum Alloy (AA) 7075 Plate Repaired by Additive Friction Stir Deposition Using AA7075 Feedstock

Abstract

In this work, Additive Friction Stir Deposition (AFSD) was employed for ballistic repair of AA7075-T6511 plates. After penetration with 7.62 × 51 mm FMJ rounds, the AA7075-T6511 plates were repaired by AFSD using the same AA7075-T6511 feedstock material. The repaired plates were impacted and penetrated with the same 7.62 × 51 mm FMJ rounds, and the surface damage characteristics including the initial and residual velocities were compared against the control wrought plates. The AFSD process successfully repaired the damaged control plates with the same alloy, without any observable defects such as large cracks or pores prior to impact tests. Although the surface appeared pristine other than milling marks, the surface damage characteristics of the repaired plates were significantly different than the control plates. The increase of spalling and petalling with the repaired material can be attributed to the thermomechanical processing of AFSD, which would alter the control T6511 temper of the feedstock due to coarsening of strengthening precipitates. A cross-sectioned repaired plate was analyzed using microhardness plots and optical microscopy to illustrate the effectiveness of the AFSD process for ballistic repair by depositing the same material into the damaged area. Despite the surface damage discrepancy, the repaired plates performed similarly to the control plates with respect to initial and residual velocities.Graphical