Microstructural Evolution for Superplasticity Using Equal-Channel Angular Pressing

Abstract

Equal-channel angular (ECA) pressing is capable of introducing an ultrafine grain size into bulk materials and the precise nature of the microstructure is dependent upon the number of pressings and the combinations of the planes for shear deformation. When the strain is sufficiently high, it is possible to achieve equiaxed fine grains with high angle grain boundaries. The number of pressings required to establish the ultimate equiaxed grains increases with an increase in the alloy content. Tensile experiments at elevated temperatures under different initial strain rates have demonstrated that ECA pressed Al-5.5%Mg-2.2%Li-0.12%Zr (Al-1420) and Al-6%Cu-0.5%Zr (Supral) show excellent superplasticity, thereby providing the potential for substantially increasing the viability of superplastic forming in the metal forming industry.