Abstract Large scale molecular dynamics simulations were carried out to simulate a particle with ductile, metallic core surrounded by a brittle, chemically inert layer impacting a metallic substrate. Both the particle and the substrate consisted of fcc single crystals. Particle impact velocities ranging from 500 m/s to 1000 m/s were considered. Despite the visible cracks, the brittle shell resisted to impact at velocities of up to 700 m/s. The breakage of the brittle shell seen for higher impact velocities exposed parts of the ductile core, allowing metal-to-metal contact with the substrate. It was found that particle adhesion requires the formation of a minimum amount of metallic bonds. Not fulfilling this condition resulted in the particle bouncing off. In this case, the formation and posterior rupture of metallic bonds that were not strong enough to keep the particle attached to the substrate eventually contributed to reduce the overall particle rebounding velocity. Particle adhesion occurred undoubtedly only for the highest velocity considered in this study, 1000 m/s. A significant degree of particle deformation, associated with usual fcc metal plasticity (i.e., creation/multiplication of dislocations), was observed for all impact velocities. Additionally, the strength of the impact caused partial destruction of the fcc crystalline structure near the particle-substrate contact zone. For the impact velocity of 1000 m/s, the flow of large portions of this amorphous material under shear resulted in jetting and, by partially removing the debris of the shattered brittle shell, large areas of metallurgical bonding, which maintained the particle adhered to the substrate. In spite of its role in the formation of metallurgical bonding, the amorphous material started to crystallize back to an fcc phase, which suggests the amorphous material was a short living, transient phase.

中文翻译：

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fcc核壳颗粒高速冲击下冶金结合的原子研究

摘要 进行大规模分子动力学模拟以模拟具有延展性金属核的粒子，该核被脆性化学惰性层包围，撞击金属基材。颗粒和基材均由 fcc 单晶组成。考虑了从 500 m/s 到 1000 m/s 的粒子撞击速度。尽管有可见的裂纹，但脆壳仍能抵抗高达 700 m/s 的速度冲击。在更高的冲击速度下，脆壳的破裂暴露了延性芯的部分，允许金属对金属与基材接触。发现颗粒粘附需要形成最少量的金属键。不满足这个条件会导致粒子反弹。在这种情况下，金属键的形成和后断裂强度不足以使颗粒附着在基材上，最终导致颗粒整体回弹速度降低。毫无疑问，仅在本研究中考虑的最高速度 1000 m/s 时才会发生颗粒粘附。对于所有冲击速度，观察到与通常的 fcc 金属塑性（即位错的产生/倍增）相关的显着程度的颗粒变形。此外，冲击强度导致颗粒-基材接触区附近的 fcc 晶体结构部分破坏。对于 1000 m/s 的冲击速度，这种无定形材料在剪切作用下的大部分流动导致喷射，并通过部分去除破碎的脆壳碎片，大面积的冶金结合，保持颗粒粘附在基材上。尽管它在冶金结合的形成中发挥了作用，但非晶材料开始结晶回 fcc 相，这表明非晶材料是一种短寿命的瞬态相。