Effect of surface severe plastic deformation on microstructure and hardness of Al alloy sheet with enhanced precipitation

The effect of severe plastic deformation on microstructure and hardness of 7075 aluminum alloy sheet presented different results from that of thick samples in previous study. Grains were not refined obviously, and precipitation phases MgZn2 were massively dissolved in the matrix in the region close to the surface. Varied density of dislocations were produced at different depths. The depth of severe plastic deformation layer was 40-70 mu m, while the affected depth of hardness was much deeper. The maximum hardness enhancement, 16% increase compared to the core hardness, appeared at about 150-250 mu m below surface. The hardness change depended on the competition between the roles of precipitation dissolution and dislocation multiplication.

Automated summary

The effect of severe plastic deformation on microstructure and hardness of 7075 aluminum alloy sheet differed from that of thick samples. Grain refinement was not significant, but precipitation phases MgZn2 were dissolved in the matrix near the surface. Varying densities of dislocations were formed at different depths. The depth of severe plastic deformation layer was 40-70 μm, while the affected depth of hardness was much deeper. The maximum hardness enhancement, a 16% increase compared to the core hardness, occurred at a depth of approximately 150-250 μm below the surface. The change in hardness depended on the competition between precipitation dissolution and dislocation multiplication.