The change in the fractal dimension of the shape of the cavities during the superplastic deformation of duralumin LY12CZ

Cavities have been widely observed during the superplastic deformation of metals and alloys, the superplasticity of metals and alloys generally being sensitive to cavity formation. However, the shape of the cavities is irregular during superplastic deformation, thus quantitative analysis of the shape of the cavities is one of the keys to the studying of the superplastic deformation mechanism. In this paper, the quantitative effects of process parameters on the fractal dimension, D_f, of the shape of cavities during the superplastic deformation of duralumin LY12CZ (approximately corresponding to ASTM 2024) with and without the application of an external electric field is studied. The experimental results show that: (i) the fractal dimension of the shape of cavities varies with the change of process parameters (deformation temperature, T, true strain, ε, initial strain rate, ε̇₀), both with and without the application of an external electric field; (ii) the fractal dimension of the shape of cavities also varies with the intensity of the electric field, E, under otherwise identical conditions. The results in this paper show that the improvement of superplasticity with the application of an external electric field is related to a lower value of the fractal dimension in the quasi-stable flow stage of superplastic deformation.