Abstract: Nanopowder consolidation under high strain rate shock compression is a potential method for synthesizing and processing bulk nanomaterials, and a thorough investigation of the deformation and its underlying mechanisms in consolidation is of great engineering significance. We conduct non-equilibrium molecular dynamics (NEMD) simulation and X-ray diffraction (XRD) simulation to systematically study shock-induced deformation and the corresponding mechanisms during the consolidation of nanopowdered Mg (NP-Mg). Two different deformation modes govern the shock consolidation in NP-Mg, i.e., deformation twinning at u_p ≤ 1.5 km s^-1 and structural disordering, at u_p ≥ 2.0 km s^-1. They accelerate the collapse of nanopores and void compaction, giving rise to the final consolidation of NP-Mg. Three types of deformation twinning are emitted in NP-Mg, i.e., the extension twinning for {11$\overline{2}$1}〈$\overline{1}$$\overline{1}$26〉, and {1$\overline{1}$02}〈1$\overline{1}$01〉, and the compression {11$\overline{2}$2}〈$\overline{1}$$\overline{1}$23〉 twinning. They are prompted via coupling atomic shuffles and slips. Deformation twinning prefers to occur within the grains as shock along 〈11$\overline{2}$0〉 or its approaching direction (A- and B-type grains), originated from the high-angle grain boundaries (HAGB) at compression stage. They are inhibited within the ones as shocking along 〈0001〉 and the approaching ones (C- and D- type grains). The release and tension loading facilitates the reversible and irreversible detwinning, for the extension and compression twinning, respectively, within the A- and B-type grains. It also contributes to a compression-tension asymmetry for twinning, i.e., release and tension induced extension twinning within the C- and D-type grains. The subsequent spallation is mediated by GB sliding and GB-induced stacking faults at u_p ≤ 1.5 km s^-1, and structural disordering at u_p ≥ 2.0 km s^-1.

Key words: Non-equilibrium molecular dynamics, Nanopowder Mg, Shock consolidation, Deformation twinning, X-ray diffraction