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Tougher and stronger alloys are desired for structural applications, but the strength-ductility trade-off limits it. In order to overcome this issue, heterogeneous structures can be developed in high-strength materials to restore an acceptable ductility for practical use. In this investigation, dissimilar alloys (1050 and 7050 aluminum alloys) were roll bonded at 450 °C and 500 °C to obtain sheets with a heterogeneous structure in terms of microstructure and composition, and the microstructure and tensile properties were investigated. The final microstructure was a combination of soft and coarse-grained 1050 Al layers together with elongated and ultrafine-grained precipitation strengthened 7050 Al layers. A simultaneous increase in strength and ductility was achieved after six cycles at 500 °C with 343 MPa of ultimate tensile strength and ∼14% of uniform elongation, which was associated with the increase in the strain-hardening rate due to the combination of a coarser and ductile microstructure in the 1050 Al layer and a fine grained and precipitation hardened 7050 Al layer. It was also demonstrated that higher interface density in the heterogeneous structure decreased the dynamic recovery rate and a better combination of strength and ductility was achieved. These findings may determine processing parameters to optimize the roll bonding technology and develop new heterostructured sheets for practical applications.

Cyclic closed-die forging (CCDF) appears to be an easy to operate deformation process, which imposes high levels of strain, even on difficult-to-deform materials. However, despite said potential advantages, the CCDF at cryogenic temperatures has not yet been investigated. Copper samples with dimensions of 10 mm × 10 mm × 20 mm were processed in up to six passes with interpass rotation, enabling the samples to return approximately to their initial dimensions after each pass. The intensity and homogeneity of plastic deformation was evaluated by mapping the Vickers hardness over the entire surface of the sample, and the resulting maps were compared with the strain and stress distribution estimated by FEM numerical simulation. The deformed microstructures were examined by optical and transmission electron microscopy. Cryogenic CCDF has proved to be effective in suppressing the recovery mechanisms of Cu samples, resulting in finer and more heterogeneous strains distribution than those deformed at room temperature. However, long-term observations by TEM have shown that these microstructures are inherently unstable, so that hardness decreases 50% after two years. Keywords: Copper, Cyclic closed-die forging, Numerical simulation, Cryogenic deformation, Microstructural stability