Effect of room temperature multi-pass ECAP deformation on mechanical properties and precipitation phase distribution of 7075 aluminium alloy

The effects of equal-channel angular pressing (ECAP) deformation on the microstructure, mechanical properties, precipitation phase distribution and precipitation behaviour of a 7075 aluminium alloy were investigated by scanning electron microscopy, X-ray diffractometry and transmission electron microscopy. The original grain size was refined from 26 µm to 4.5 µm, the tissue distribution was more uniform, and the percentage of high-angle grain boundaries was increased from 8.1% to 48.1%. After ECAP deformation, the deformed grains gradually transformed into sub-crystalline and recrystallised microstructure, the dislocation density was reduced by dynamic recrystallisation, the original rolled β -fibre weave transformed into a C-type shear texture, and the precipitated phase particles gradually broke and refined before being distributed in the matrix. The strength and hardness of the original base material were greatly enhanced by combined second-phase and dislocation strengthening effects, but its plasticity was reduced and a mixed brittle-ductile fracture mode is observed.