INFLUENCE OF REPEATED SHOCK LOADING ON THE SUBSTRUCTURE EVOLUTION OF 99.99 WT-PERCENT-ALUMINUM

An electron microscopy study has been conducted of the substructure evolution of large-grained (3 mm) polycrystalline 99.99 wt.% Al subjected to single- and repeated-shock loading excursions at - 180-degrees-C. Single-shock loading of aluminum is seen to form dislocation cells with a high density of vacancy loops. The substructure evolution in aluminum with repeated-shock loading is observed to be progressive in nature and similar to the dislocation arrangements in f.c.c. single crystals and polycrystals with increasing strain. The substructure evolution, from dislocation cells to planar slip bands to microbands, is found to be particularly evident adjacent to grain boundaries. The substructure evolution in high purity aluminum subjected to repeated-shock loading at low temperature is discussed in terms of the deformation mechanisms, in particular vacancy loop and microband formation, and compared with previous studies on shock-deformed aluminum.