Improved tensile properties in heterostructured 1050/7050 Al sheets produced by accumulative roll bonding

Abstract

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.