l-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr铝合金挤压材的性能

Effect of solid solution-T652 treatment and pre-recovery-solid solution-T652 treatment on microstructure and mechanical properties of an extruded Al- alloy Al- 10.78Zn- 2.78Mg- 2.59Cu- 0.22Zr-0.047Sr was studied. The results show that after a pre-recovery-annealing treatment and then a post-aging at 121oC for 24 h the grain size of the extrusion can be refined from 9.76 m to 5.56 m; the average grain boundary angle can be reduced from 23.59 to 17.41, i.e.the percentage of low angle grain boundary is significantly enhanced from 53% to 67%, therewith, the dislocation strengthening is increased, and the recrystallization process may be suppressed. Compared with solid solution-T652, the pre-recoveryannealing treatment can enhance the corrosion resistance of the alloy, i.e. the maximum corrosion depth may be reduced from 125.0 m to 91.4 m, thus its exfoliation corrosion rating increased from EB to EA grade, while the alloy maintained a high strength. The strength of the alloy after the pre-recovery-solid solution plus T652 treatment is up to 728 MPa. Dislocation strengthening and low angle grain boundary strengthening are the main strengthening mechanisms.