纳米W粉冲击烧结的分子动力学模拟

粉末冲击烧结是制备高品质W的一种有效方法，而分子动力学方法在尺度极小、过程迅速的数值模拟上有着独特的优势。因此运用分子动力学方法，结合W的嵌入原子势，对常温下的纳米W粉末的冲击烧结过程进行模拟，得到颗粒微观压实过程图、体系速度分布云图、p-U_p、T-U_p、T-p曲线以及径向分布函数。研究了不同颗粒速度及产生的射流对纳米W粉末冲击烧结影响，分析了微观冲击烧结机理。结果表明，低速冲击条件下（500 m/s以下），纳米颗粒无法压实。高速条件下（1 000 m/s及以上），颗粒能获得致密化很高的压实。颗粒间的相互挤压造成的高应力使颗粒表面的原子发生流动变形，原子向颗粒间空隙流动，形成压实。颗粒间产生的射流以及高速冲击导致的颗粒熔化，均促进烧结获得致密度更高的烧结体。

Molecular dynamics simulation of shock consolidation of nano tungsten powder

Shock consolidation of powders is an effective method for fabrication of the high quality tungsten, and molecular dynamics simulation has unique advantages in modelling the rapid process at atomic-scale. In this work, the shock consolidation of nano tungsten powders at room temperature was studied by molecular dynamics using the embedded atomic potential of tungsten. The morphology of the compressed particles, distribution of particle velocity, p-U_p, T-U_p, T-p curves and radial distribution function were investigated to analyze the effects of particle velocity and jets on the shock consolidation. The mechanism of consolidation was also proposed at micro-scale. The results showed that the nanoparticles could not be compacted to full density at a relatively low impact velocity (＜500 m/s), while a good densification could be achieved at high impact velocity (＞1 000 m/s); the high pressure due to the extrusion between particles leads to flow and deformation on the surface of the particle. The voids among the particles were filled by the flowing atoms, leading to densification. Particles were melted during the impacts by adjacent particle and jet, which promotes the sintering between particles.