title: Directional amorphization of boron carbide subjected to laser shock compression.
abstract: Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45∼50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.
authors.affiliation: University of California, San Diego, La Jolla, CA 92093.
authors.forename: Shiteng
authors.initials: S
authors.lastname: Zhao
authors.affiliation: University of California, San Diego, La Jolla, CA 92093.
authors.forename: Bimal
authors.initials: B
authors.lastname: Kad
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, CA 94550.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Remington
authors.affiliation: United States Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD 21005.
authors.forename: Jerry C
authors.initials: JC
authors.lastname: LaSalvia
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, CA 94550.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Wehrenberg
authors.affiliation: United States Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD 21005.
authors.forename: Kristopher D
authors.initials: KD
authors.lastname: Behler
authors.affiliation: University of California, San Diego, La Jolla, CA 92093; mameyers@eng.ucsd.edu.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Meyers
keywords: amorphization; boron carbide; lasers; shock wave