Mechanical behavior and microstructure evolution of high-purity aluminum with different grain sizes under shock loading

Mechanical behavior and microstructure evolution of high-purity aluminum with different grain sizes under shock loading were investigated systematically through plate impact experiments, microstructure and texture characterization, and hardness and compression tests. The results show that the mechanical behavior, microstructure and texture are significantly influenced by the impact velocity and grain size. As the impact velocity increases, the peak shock stress and adiabatic temperature rising almost exhibit an upward trend; however, the Hugoniot elastic limit (HEL) stress is slightly affected by the impact velocity. The grain size almost has no effect on the HEL stress and peak shock stress. Shock compression can considerably change the microstructure, which is highly relied on the impact velocity and grain size. Independent of the grain size, as the peak shock stress increases, low angle grain boundaries (LAGBs), dislocations and subgrains increase continuously at first, and then those microstructural features vanish and are replaced by numerous ultra-fine grains. In spite of this, the peak shock stress sensitivity of high-purity aluminum is dependent on the grain size. Shock compression can also significantly affect texture. The preferred orientations always change with increasing peak shock stress, and the texture intensity remains constant at first, then increases, and finally decreases. Independent of the grain size, the hardness and yield strength always increase continuously with increasing impact velocity. Moreover, the relationship between yield strength and grain size does not always follow the Hall-Petch relationship.