159 / 2023-04-14 23:03:04

Dislocation structure and lattice dynamic in shock-compressed single crystal Aluminum

aluminum,shock loading,dislocation structure,plasticity mechanism,TXRD,molecular dyamics

高压物理与材料科学 > 动高压-II

Dislocation structure and lattice dynamic in shock-compressed single crystal Aluminum

Mengyang Zhou, Qiannan Wang, Jianbo Hu^*

 National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China

jianbo.hu@caep.cn(JH)

Abstract:

Understanding dynamic plastic response of materials is the key to develop physics-based constitutive models for extreme conditions, including asteroid impact sites, ballistic penetrators and armor protection. At lattice level, the fundamental mechanism of plastic deformation are dislocation slip, twinning and phase transition, but it is still challenging to figuring out the dominant defect behavior during shock loading. Nowadays, time-resolved X-ray diffraction (TXRD) methods with high spatial and temporal resolution can provide atomic-level evolution, and promoting the insights into competing deformation mechanisms. In this work, by a combined research of the TXRD experiments and MD simulation, dynamic dislocation structures and plasticity mechanisms of single crystal aluminum are intensively investigated. Laser-driven shock loading was applied along both [100] and [110] crystal orientation with a peak pressure of 8 GPa while a pink Laue pattern was captured at various delay time. The diffraction spots of [100] sample exhibit hazy broadening during shock loading, whereas those in [110] direction exhibit trailing and splitting, corresponding to slip activities and sub-grain formation respectively. Diffraction pattern emulation was also performed and the results show that the incipient plasticity in [110] direction is dominated by single slips of partial dislocation, which is further confirmed in MD simulation. For [100] direction, although the main defect events are controlled by partial dislocation, conjugated double slips are activated. Besides, a sheared slip plane between adjacent double-slip domains is also observed in [100] direction, which may enhance the deformation capability as well as suppress sub-grain formation, and result in simply broadening diffraction spots.