Rigid-thermoviscoplastic finite-element analysis of the semi-solid forgingof A12024

In the present investigation, material characterization of globular Al2024 alloy in terms of breakage ratio, solid-fraction, strain and strain rate wa s obtained at the semi-solid state through backward extrusion experiments. Axisymmetric rigid-thermoviscoplastic finite-element analysis of semi-solid forging of a ball-joint case was performed using the currently determined flow stress. In the analysis, the solid-fraction considering phase change w as updated at each time increment by calculating the volume of the liquid c omponent under the assumption that the relative flow of liquid to solid com ponents obeys D'Arcy's law. The simulation results were compared to those o f the experiments to test the validity of the currently determined flow str ess. In addition, the effects of process variables such as die preheating a nd initial workpiece temperatures and forming speed on formability were inv estigated. It was construed that the forming speed was the most dominant pr ocess variable in effecting variation in the distribution of solid-fraction . (C) 1999 Elsevier Science S.A. All rights reserved.