Effect of hot deformation on grain structure and quench sensitivity in 7085 aluminum alloy

Abstract

The effect of hot deformation on the quench sensitivity of the 7085 alloy was studied through hardness testing and microstructure characterization. The findings indicate that hot deformation enhances the quench sensitivity of the 7085 alloy, with the hardness difference between water quenching and air cooling increasing from 5.4% (before hot deformation) to 10.4% (after hot deformation). In the undeformed samples, the Al₃Zr particles within the grains exhibit better coherent with the Al matrix. During slow quenching, only the η phase is observed on Al₃Zr particles and at the grain boundaries. Hot deformation leads to a mass of recrystallization and the formation of subgrains with high dislocation density. This results in an increase in the types, quantities, and sizes of heterogeneous precipitates during quenching. In the slow quenching process, high angle grain boundaries are best for the nucleation and growth of the η phase. Secondly, a substantial quantity of η and T phases precipitate on the non-coherent Al₃Zr phase within the recrystallized grains. The locations with high dislocation density subgrains (boundaries) serve as nucleation positions for the η and T phases precipitating. Additionally, the Y phase is observed to precipitate at dislocation sites within the subgrains.

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