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在现场测量冲击波驱动的结合和格子动态的X射线衍射

C E Wehrenberg¹, D McGonegle², C Bolme³

¹Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.

|October 27, 2017

概括

新的X射线衍射实验揭示了冲击波如何在原子层面变形材料. 这项研究捕捉了在极大压力下结合和滑动的机制,为材料科学和高能量密度物理学提供了洞察力.

科学领域:

固态物理
材料科学
高压物理

背景情况:

冲击波会导致材料的极端变形和缺陷, 这对于理解行星形成到材料性能的现象至关重要.
在冲击压缩下区分结合和滑动,这是主要的塑料变形机制,在实验中具有挑战性.
之前的方法受到冲击后火器件和适度的压力范围的限制,阻碍了对抗变形机制的详细分析.

研究的目的:

在冲击压缩过程中开发和演示在位X射线衍射技术以捕获格子级微结构过程.
调查在冲击负荷下的主导变形机制,解决与此前发现的矛盾问题.
在极端压力下对物质行为提供洞察力,

主要方法:

使用X射线衍射实验以测试动态,格子级微观结构变化.
压缩体中心立方体材料, 选择其高冲击阻抗和X射线不透明.
在现场分析数据以观察冲击波传播期间的微结构过程和格子动态.

主要成果:

在中观察到的结合和相关的格子旋转发生在几十个皮秒的时间尺度上.
在变形机制中确定了压力依赖的过渡,在压力超过150千兆帕斯卡的压力下,脱位滑动占主导地位.
证明了该技术在传统回收实验无法达到的压力状态下获得变形物理的能力.

结论:

五秒分辨率的X射线衍射提供了前所未有的现场,格子层面的洞察力.
这项研究解决了有关变形的相互矛盾数据,揭示了在高压下从结合转变为滑动主导的可塑性.
这种先进的技术广泛适用于研究冲击波,高应变率现象以及各种材料的可塑性诱导过程.

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