The role of aging on the mechanical and microstructural response of aluminum 6061 to one-dimensional shock loading

The shock response of the aluminum alloy 6061, and its variation according to heat treatment have been monitored via the placement of stress gauges in such orientations so as to be sensitive to the lateral component of stress, and hence the shear strength. To complement these measurements, the postshock microstructure and mechanical response have also been determined via full one-dimensional recovery techniques. Results have shown that the solution treated (T0) state, as a largely single phase material displays a fast rising shock pulse with a significant degree of hardening behind the shock front. This indicates that a high degree of dislocation generation is expected. Postshock analysis of recovered samples has confirmed this hypothesis, with dislocation cells being observed and a notable increase in the yield strength in comparison to the as-received material. In contrast, the aged (T6) experiments showed a much longer rise time with a lower degree of hardening behind the shock front. Microstructural analysis postshock shows a more randomized dislocation distribution, with little or no postshock hardening occurring once the shock induced strain has been accounted for. This has been attributed to the presence of fine Mg2Si precipitates inhibiting the motion and generation of dislocations. These measurements are in agreement with work previously carried out on this material. Comparison of the shear strengths of the two heat treatments also shows that although the T6 condition is a little higher than T0, the differences are somewhat lower than expected. [doi:10.1063/1.3490135]