Abstract
The microstructure evolution of single crystal Al under shock loading is investigated using both numerical simulations and shock wave theory. Using momentum mirror method with loading velocity in the range of 0.8 similar to 1.2 km/s, the results show the generation of a split two-wave structure, in which the (fcc -> bcc) transition wave and preceding elastic precursor are connected by the plastic zone. The Hugoniot state of the body-centered phase does not deviate from the theoretical Hugoniot curve considering both the lattice vibration and thermal activation of electrons. The metastable bcc phase would change into fcc phase again once the uniaxial stress is released during the unloading stage. For shock loading tests with piston velocity larger than 1.5 km/s, the shock Hugoniot would enter into melting state. While the impact velocity is larger than 4.0 km/s, solitary wave can propagate stably at the shock front. Further analysis of wave velocity show that the competition between the transition wave propagation and dislocation mobility determines the full development of plastic zone. This new finding suggests that the dynamic response of solids might be tuned by engineering the distribution of microstructures to control the dislocation multiplication.
NSTL
Elsevier