In the present investigation, material characterization of globular Al2024 alloy in terms of breakage ratio, solid-fraction, strain and strain rate was 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 was updated at each time increment by calculating the volume of the liquid component under the assumption that the relative flow of liquid to solid components obeys D'Arcy's law. The simulation results were compared to those of the experiments to test the validity of the currently determined flow stress. In addition, the effects of process variables such as die preheating and initial workpiece temperatures and forming speed on formability were investigated. It was construed that the forming speed was the most dominant process variable in effecting variation in the distribution of solid-fraction. (C) 1999 Elsevier Science S.A. All rights reserved.