Shock compaction and characterization of nanocrystalline materials via planar shock wave

Abstract

Nanocrystalline materials have been widely focused for the interesting subject of research for a few of decades, and their understanding have been advanced significantly in the last few years. Nanocrystalline materials are structurally characterized by a large volume fraction of grain boundaries, which may significantly alter their physical, mechanical, and chemical properties in comparison with conventional coarse-grained polycrystalline material because of the change of the volume fraction of inter-crystal regions and triple-junctions. Thus, nanocrystalline materials provide industrial or commercial applications an attractive potential with their novel properties mentioned above. A number of techniques have suggested and explored for couple of decades to produce nanostructured materials, but most of them takes a multiple processes and long time to achieve bulk specimen. Moreover, the inevitable heat-treatment to bond particles with each other promotes the grains to grow. Single-step consolidation of powders using high pressure shock-waves generated by planar impact or explosives is considered to be a potentially important method for the synthesis and processing of bulk nanocrystalline materials. The shock-wave compaction (SWC) processes occur during on microsecond timescale and involve the heterogeneous deposition of shock energy, resulting in interparticle bonding and configurational changes in particles, such as the dislocations, subgrains, distorted regions and partially melted regions. Thus, SWC-processed dense monolithic bulks or composites are considerably different from samples densified conventionally via powder processing techniques that involve additional sintering steps at high temperature. Rapid consolidation of powders by SWC can form bulk material that retaining the nanosize of the powder without any substantial grain growth In this study, nanocrystalline bulk materials were fabricated by planar shock wave compaction technique without addit...