Wang Zhixiu

Ostwald Ripening Behavior of Al8CeCu4 Phase in Al-14Cu-7Ce Alloy

Abstract The Ostwald ripening behavior of Al 8 CeCu 4 phase in the Al-14Cu-7Ce alloy annealed at elevated temperatures was investigated using hardness testing, scanning electron microscopy, image analyses and physical modeling. Results indicate that the average radius of Al 8 CeCu 4 particles increases while the hardness of the alloy decreases with increasing of annealing temperature and time. The ripening process of Al 8 CeCu 4 phase is mainly controlled by the volume diffusion of Ce. The ripening kinetic of Al 8 CeCu 4 particles satisfies well the modified Lifshits-Slyozov-Wagner theory, taking into account the effect of the volume fraction of Al 8 CeCu 4 particles. The volume diffusion coefficient of Ce and the interfacial energy between the matrix and Al 8 CeCu 4 phase were also calculated based on the general rate equation.

Spheroidizing Behavior of the Lamellar Al8CeCu4 Phase in Al-14Cu-7Ce Alloy

The spheroidizing behavior of the lamellar Al8CeCu4 phase in the Al-14Cu-7Ce alloy annealed at elevated temperatures was investigated by microstructure observation, hardness testing and theoretical calculation. Results show that with increasing the annealing temperature, the spheroidizing process of the Al8CeCu4 phase is accelerated. The controlling element for the spheroidizing process is determined to be Ce by theoretical calculation using the general rate equation. Microstructure observation indicates that the spheroidizing process of the Al8CeCu4 phase includes two successive steps, i.e., the curved lamella breaking into long rods by Gibbs-Thompson effect and then the rods separating into spherical particles further by Rayleighs capillary induced perturbation mechanism.

Modeling for Predicting Flow Stress of Al-14Cu-7Ce Alloy at Elevated Temperature

Abstract Isothermal hot compression tests of annealed Al-14Cu-7Ce alloy were carried out on Gleeble-3500 system in the temperature range from 573 K to 823 K and the stain rate range from 0.001 s −1 to 1 s −1 . The resulted true stress-true strain data were employed to establish a constitutive equation for predicting high temperature flow stress. The results show that the flow stress follow well the rate equation ɛ ˙ = A D L G b / κ T [ sinh ( α L σ / G ) ] n . The effect of strain was taken into account by fitting of polynomials into the material parameters A , α L and n . The proposed constitutive equation can predict precisely high temperature flow stress of Al-14Cu-7Ce alloy. The control mechanism of hot deformation is dislocation climb.