The mechanical behavior of nanofoam aluminum with low porosity(~3.3%)subjected to high rate(~2×109s-1)uniaxial compression was investigated using molecular dynamics(MD)simulations.The deformation was applied along the [100],[110] and [111] crystallographic orientations.At the onset of plastic deformation,pores acted as the source of dislocation nucleation,the leading Shockley partial dislocations nucleated at the same strain(3.8%)independent of applied loading directions.Due to the emission of trail partials,the accumulation of dislocation density can be divided in slow multiplication stage and fast multiplication stage by the dislocation density multiplication rate dρd/dε.There is a post-yield softening corresponding to the onset of rapid dislocation density multiplication at higher dislocation densities.When the loading direction was in [100] or [111],the dislocations were mainly consist of mobile dislocations,while when subjected to [110] compression,the mobile dislocation density was about one magnitude lower than the total dislocation density.Prismatic dislocation loops were formed gliding along loading direction when the loading was in [110],probably because of sufficient space for prismatic loops formation.These results reveal the significant influence of loading orientations on the patterns of dislocation movements.