Hypervelocity impact induced deformation modes in α-alumina

Hypervelocity impact deformation mechanisms of alpha-alumina are studied using 540x10(6) atom molecular dynamics simulation on massively parallel computers. The projectile impact on the (0001) surface of alpha-alumina at 18 km/s exhibits a fundamentally different symmetry of the deformation patterns from those under lower strain rates. The simulation reveals a sequence of atomistic deformation mechanisms following localized melting and amorphization. These include pyramidal slips, basal slips and twins, rhombohedral twins, and twins along the {0 (1) over bar 11}. Some of these deformation patterns are not observed under lower impact velocities. (C) 2007 American Institute of Physics.