Strong and ductile Al-Zn-Mg-Zr alloy obtained by equal angular pressing and subsequent aging

An ultrafine-grained Al-Zn-Mg-Zr alloy with superior mechanical performance was obtained by high passes of equal angular pressing (ECAP) and subsequent aging. After 8 ECAP passes and aging, the yield strength (YS) and ultimate tensile strength (UTS) of the solid-solutioned alloy are significantly improved from (98 +/- 10) and (226 +/- 7) MPa to (405 +/- 9) and (427 +/- 9) MPa, respectively. A large elongation is also maintained ((17.4 +/- 2.5)%). The microstructure features including grain refinement, morphology of precipitates, and dislocation density, were revealed with multiscale characterizations, including transmission electron microscopy, electron backscattered diffraction, and X-ray diffraction. After 8 passes of ECAP, the original coarse elongated grains are refined to a unique bimodal grain structure consisting of ultrafine equiaxed and lath-like grains. Additionally, the effects of ECAP and subsequent aging on the strengthening contribution of a variety of strengthening mechanisms, such as dislocation strengthening and precipitation strengthening, were discussed in detail.

Automated summary

An ultrafine-grained Al-Zn-Mg-Zr alloy with superior mechanical performance was obtained through high passes of ECAP and subsequent aging. The microstructure features, including grain refinement, morphology of precipitates, and dislocation density, were improved. After 8 passes of ECAP, the original coarse elongated grains were refined to a unique bimodal grain structure consisting of ultrafine equiaxed and lath-like grains.