Nanocrystalline structure fabricated by cryogenic temperature rolling of AA 2099 aluminum alloy.

• Nanocrystalline structure was produced by cryogenic rolling in an AA 2099 alloy. • Ultrafine structure was observed inside or near the regulate-oriented shear bands. • Severely deformation and related temperature increase leads to the grain refinement. • Shear banding was promoted due to strong work hardening at cryogenic temperature. Solid solution treated AA 2099 alloy was rolled by a total reduction of 80% at both room and cryogenic temperature. Results show that nanocrystalline grain structure with a size around 20–100 nm was only observed in the cryogenic temperature rolled sample at high rolling strain. The formation of those nanograins related to shear banding behavior. Shear banding behavior was greatly promoted by cryogenic temperature rolling, which had a strong influence on mechanical homogeneity of rolled samples. The width of these high-density shear bands is around 0.2–8 µm. Shear strain partitioning between slip and shear banding was depended on slip behavior in deformed grains. Strain concentration inside shear bands may give rise to an obvious temperature increase, which caused significant grain refinement in or near the shear bands. The growth of nano-grains is retarded due to limited heat and pinning effect of nanosized precipitation. [ABSTRACT FROM AUTHOR]