Effect of Multi-pass Compression on the Microstructure of 7 085 Aluminum Alloy

Abstract

The isothermal compression tests of 7 085 aluminum alloy were carried out on Gleeble-3 800 thermal simulator by two-pass (30% per-pass) and three-pass (20% per-pass) at 300–400 °C and the strain rate of 0.01 s⁻¹. The effect of compression strategy on microstructure evolution of 7 085 aluminum alloy was analyzed by optical microscopy (OM) and electron backscattering diffraction (EBSD). The results show the softening mechanism of 7 085 aluminum alloy is mainly recovery, the recrystallization degree is sluggish when the samples deform at 300 °C. The fraction of recrystallized grains just reaches 23.2% at a higher deformation temperature of 400 °C, while a large amount of sub-grains with equiaxed morphology are formed inside the deformed grains. Different deformation paths have a significant effect on the microstructure evolution of the 7 085 aluminum alloys, and more uniform and fine microstructures are obtained at the three-pass deformation. In addition, a short holding time of 5 s is not enough to trigger the static recrystallization. When the holding time reaches 120 s, the dislocations rearrange and a large number of recrystallized grains and regular sub-grains appear inside the original grain. In a word, more uniform and fine microstructures are obtained at three-pass deformation at 400 °C and 120 s of 7 085 aluminum alloy.

Keywords

7085 aluminum alloy / multi-pass hot deformation / microstructure evolution / recrystallization