Achieving high strain rate superplasticity of an Al-Mg-Sc-Zr alloy by a new asymmetrical rolling technology

Superplastic property and microstructure evolution during the deformation of an Al-6.10Mg-0.25Sc-0.1Zr alloy with fine grains, produced by a new asymmetrical rolling technology, were investigated by tensile tests and microscopy methods. The results show that new asymmetrical rolling can considerably enhance the high strain rate superplasticity. A maximum ductility of 3200% can be achieved at 500 °C and 5×10−2 s−1. Under the same cold rolling reduction (75%), although the maximum elongation is comparable to that of the traditionally rolled same materials, asymmetrical rolling can increase the optimum strain rate up to 10 times. The microstructure results show that, during superplastic deformation, low angle grain boundaries gradually transfer into high angle grain boundaries and the grains gradually orientate randomly. The excellent high stain rate superplasticity can be ascribe to the refined grains and the presence of nano-scaled Al3(Sc, Zr) particles which can stabilize the fine-grains during hot deformation. The grain boundary sliding is the predominant superplastic deformation mechanism in the studied alloy.