Study of dislocation walls evolution during spall in pure aluminum

The micro-structure of the spall plane of pure aluminum (99.9999{\%}) was investigated in symmetric plate impact experiments. The aluminum targets were first heated at 450$^{o}$C for 22 h for grain growth. The impacted targets were softly caught and collected for metallurgical analysis. It was found that at weak impacts with partial spall, voids with average size of 50$\pm $10 $\mu $m were developed along the grain boundaries. The grain size in the vicinity of the voids is 50-250 $\mu $m, smaller than their size in the rest of the specimen: 400-1000 $\mu $m, revealing that the grains split into smaller grains when dynamic tension is applied. Transmission Electron Microscopy (TEM) and electron diffraction revealed evaluation of parallel dislocation walls, that create a sub-grain micro-structure inside grains with (011) orientation. In grains with other orientations no dislocation walls or sub-grain structure was found. These findings reveal a dislocation glide mechanism along {\{}111{\}} planes during the spall process in an fcc aluminum.