Revealing the microstructure evolution mechanism and mechanical responses of a novel Al-Zn-Mg-Cu alloy by hot deformation process

The effect of hot rolling with different rolling deformations on the microstructure evolution and improvement of mechanical properties of the novel Al-Zn-Mg-Cu alloy are investigated via optical microscope (OM), scanning electron microscope (SEM), electron backscattered diffusion (EBSD) and transmission electron microscope (TEM). The findings showed that the equiaxed grains with low dislocation density gradually elongate to become fibrous with high dislocation density as hot rolling deformation growing, and the dynamic dissolution of precipitations occurs at the grain boundaries of small dynamic recrystallization (DRX) grains. Dislocation entanglement is formed when a high density of dislocation is clearly visible following various rolling deformations. Dislocation cells could evolve into sub-grains, and ultimately become recrystallized grains as a result of continuous energy absorption. The percentage of low angle grain boundaries (LAGBs) with varying rolling deformation increases swiftly then declines slightly which linked to more deformed grains and sub-grains, as well as less recrystallized grains. High angle grain boundaries (HAGBs), however, show the opposite pattern. Ultimate tensile strength (UTS) and yield strength (YS) of the alloys reach peaks at deformation of 90% (UTS: 620.0 MPa, YS: 583.7 MPa). Which is predominantly attributed to the texture enhancement, grain refinement, and pinning effect of Al3(Sc, Zr, Ti) particles of L12 structure on the grain boundaries and dislocations.