An asymmetric cryorolling technique was used to reduce the thickness of an Al-Mg-Si alloy sheet from 1.5 mm to 0.19 mm. The samples were subsequently aged for 48 h at 100 degrees celcius. The hardness and tensile strength of both rolled and aged sheets increased with the number of passes up to the sixth pass, but the tensile stress decreased after the seventh pass. Investigation of the microstructure of the sheets showed that the grain size after seven passes was about 235 nm and revealed the presence of Fe-Cr-Mn-Si particles in the samples. The deformation of Fe-Cr-Mn-Si particles and sheet thickness affects the ductility when the sheet thickness is less than 0.4 mm, and the strength when the thickness is less than 0.2 mm. An asymmetric cryorolling technique was used to reduce the thickness of an Al-Mg-Si alloy sheet from 1.5 mm to 0.19 mm. The samples were subsequently aged for 48 h at 100 1C. The hardness and tensile strength of both rolled and aged sheets increased with the number of passes up to the sixth pass, but the tensile stress decreased after the seventh pass. Investigation of the microstructure of the sheets showed that the grain size after seven passes was about 235 nm and revealed the presence of Fe-CrMn-Si particles in the samples. The deformation of Fe-Cr-Mn-Si particles and sheet thickness affects the ductility when the sheet thickness is less than 0.4 mm, and the strength when the thickness is less than 0.2 mm.

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Interest in ultrafine-grained (UFG) materials has grown rapidly in past 20 years. This review focuses on the application of special rolling techniques for improvement of the mechanical properties of UFG metal sheets. These techniques include asymmetric rolling, cryorolling, asymmetric cryorolling, cross-accumulative roll bonding, and skin-pass rolling. The techniques also include a combination of processes such as equal channel angular press and subsequent rolling, combined high-pressure torsion and subsequent rolling, as well as combined accumulative roll bonding and subsequent asymmetric rolling. We also discuss the main mechanisms leading to improvement in the ductility of UFG materials related to the special rolling techniques. properties of ultrafine-grained (UFG) metal sheets. These techniques include asymmetric rolling, cryorolling, asymmetric cryorolling, cross-accumulative roll bonding and skin-pass rolling. The techniques also include a combination of processes such as equal channel angular press and subsequent rolling, combined high pressure torsion and subsequent rolling, as well as combined accumulative roll bonding and subsequent asymmetric rolling. We also discuss the main mechanisms leading to improvement in the ductility of UFG materials related to the special rolling techniques.

It is well known that when coarse-grained metals undergo severe plastic deformation to be transformed into nano-grained metals, their ductility is reduced. However, there are no ductile fracture criteria developed based on grain refinement. In this paper, we propose a new relationship between ductile fracture and grain refinement during deformation, considering factors besides void nucleation and growth. Ultrafine-grained Al-Mg alloy sheets were fabricated using different rolling techniques at room and cryogenic temperatures. It is proposed for the first time that features of the microstructure near the fracture surface can be used to explain the ductile fracture post necking directly. We found that as grains are refined to a nano size which approaches the theoretical minimum achievable value, the material becomes brittle at the shear band zone. This may explain the tendency for ductile fracture in metals under plastic deformation.