Mechanical behavior and microstructure evolution of different aluminum materials under shock loading

The mechanical behaviors and microstructure evolutions of different aluminum materials including high-purity aluminum, 7075 aluminum alloy and selective laser melted (SLM) AlSi10Mg alloy under shock loading were investigated through plate impact experiments and microstructure characterization. The results show that the Hugoniot elastic limit stress has nothing to do with impact velocity, but is related to material type; the peak shock stress significantly increases with increasing impact velocity and is somewhat affected by material type. The microstructure variation is highly dependent on the material type. In the 7075 aluminum alloy and selectively laser melted (SLM) AlSi10Mg alloy with relatively high strengths, the microstructure, including the grain size, grain shape and misorientation angle, is slightly influenced by the impact velocity. In high-purity aluminum with low strength, the microstructure is closely related to the impact velocity. As the impact velocity increases, dislocations, elongated subgrains, equiaxed subgrains and a fraction of low angle grain boundaries (LAGBs) first increase and then decrease, accompanied by the formation of numerous ultrafine equiaxed grains with sizes in the range of 1–5 μm. The limited adiabatic temperature rise during high-velocity impact cannot affect the microstructure. High rate loading was confirmed as an effective and promising method to refine grain structure for low strength materials.