Formation of Deformation Twins in Al via a Mach Wave Shock Loading Path

Since 1955 numerous researchers have probed the substructure evolution in shock-loaded single and polycrystalline Al with no twins observed. In the current study, a [100] high purity Al single crystal was shock loaded in a target assembly comprised of three machined pieces, the sample a [100] oriented Al single crystal and two surrounding concentric tantalum rings. Due to this configuration, the stress path in the [100] Al single crystal starts at 5.7 GPa but transitions to the peak stress state given by the Ta impactor hitting the Ta ring surrounding the Al crystal at the impact velocity which is ~ 14 GPa. The central [100] Al crystal cylinder thereafter rings up via lateral Mach waves such that the Al crystal sees a complex biaxial strain field and higher shear stresses. In this talk, the substructure evolution in the [100] Al single crystal is presented.