Effect of strain-modified particles on the formation of fined grains and the properties of AA7050 alloy

With a new two-pass deformation, a fine-grained AA7050 alloy was obtained owing to small particles which can affect the grain refinement. The banded structures were produced in the elongated grain interiors after the 1st-pass deformation at 300 °C. And deformation bands containing dislocation arrays and small spherical particles were obtained. A few new fined grains appeared along the elongated grain boundaries. After the 2nd-pass deformation at 430 °C, isolated chains of new fine grains were developed in the elongated grain interiors. The boundary glide and the increase of grain boundary misorientation due to cumulative strain could refine the elongated grains. The pinning effect of the particles accelerated the formation of deformation bands. The increase of deformation temperature promoted the rapid evolution of grain refinement during the deformation. The strength of the fine-grained AA7050 alloy was enhanced while the ductility was decreased.

► New fine grains were produced owing to the particles by two-pass deformation.
► The deformation mechanism is HAGB glide and increase of LAGB misorientation.
► The strength of fine grains was increased while the elongation was decreased.
► A model for effect of particles on formation of fined grains was proposed.