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 $\le$ 1.5 km s⁻¹ and structural disordering, at u_p $\ge$ 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 $\left\{11\overline{2}1\right\}〈\overline{1}\overline{1}26〉$, and $\left\{1\overline{1}02\right\}〈1\overline{1}01〉$, and the compression $\left\{11\overline{2}2\right\}〈\overline{1}\overline{1}23〉$ 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 $\le$ 1.5 km s⁻¹, and structural disordering at u_p $\ge$ 2.0 km s⁻¹.

中文翻译：

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纳米粉末 Mg 中的冲击固结和散裂：由变形孪晶和无序贡献


高应变速率冲击压缩下的纳米粉末固结是合成和加工块状纳米材料的潜在方法，深入研究其变形及其固结的潜在机制具有重要的工程意义。我们进行非平衡分子动力学 （NEMD） 模拟和 X 射线衍射 （XRD） 模拟，以系统研究纳米粉末 Mg （NP-Mg） 固结过程中的冲击诱导变形和相应机制。两种不同的变形模式控制着 NP-Mg 中的冲击固结，即 u_p 1.5 km ^s-1 处的变形孪生和 u_p 2.0 km ^s-1 处的结构无序。它们加速纳米孔的塌陷和空隙压实，导致 NP-Mg 的最终固结。NP-Mg 中发出三种类型的变形孪晶，即、$\left\{11\bar{2}1\right\}〈\bar{1}\bar{1}26〉$ 和 $\left\{1\bar{1}\mathrm{02\; 的扩展双胞胎}\right\}〈1\bar{1}01〉$，和压缩 $\left\{11\bar{2}2\right\}〈\bar{1}\bar{1}23〉$孪 晶。它们通过耦合原子 shuffle 和 slips 进行提示。变形孪晶多发生在晶粒内部，表现为沿 $\mathrm{〈11}\bar{2}0〉$或其接近方向（A 型和 B 型晶粒）的冲击，起源于压缩阶段的大角度晶界 （HAGB）。它们在沿 $〈0001〉$ 令人震惊的那些和接近的那些（C 型和 D 型颗粒）中受到抑制。释放和拉伸载荷促进了 A 型和 B 型晶粒内的可逆和不可逆解缠，分别用于拉伸和压缩缠绕。 它还有助于孪晶的压缩-张力不对称性，即 C 型和 D 型晶粒内的释放和张力诱导的延伸孪晶。随后的散裂是由 u_p 1.5 km ^s-1 的 GB 滑动和 GB 诱导的堆积断层以及 u_p 2.0 km ^s-1 的结构无序介导的。