title: Microscopic view of structural phase transitions induced by shock waves.
abstract: Multimillion-atom molecular-dynamics simulations are used to investigate the shock-induced phase transformation of solid iron. Above a critical shock strength, many small close-packed grains nucleate in the shock-compressed body-centered cubic crystal growing on a picosecond time scale to form larger, energetically favored grains. A split two-wave shock structure is observed immediately above this threshold, with an elastic precursor ahead of the lagging transformation wave. For even higher shock strengths, a single, overdriven wave is obtained. The dynamics and orientation of the developing close-packed grains depend on the shock strength and especially on the crystallographic shock direction. Orientational relations between the unshocked and shocked regions are similar to those found for the temperature-driven martensitic transformation in iron and its alloys.
authors.affiliation: Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. kkadau@lanl.gov
authors.forename: Kai
authors.initials: K
authors.lastname: Kadau
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Germann
authors.forename: Peter S
authors.initials: PS
authors.lastname: Lomdahl
authors.forename: Brad Lee
authors.initials: BL
authors.lastname: Holian