Development of Forging Processes of Magnesium Alloys on Servo Press

Forging methods for commercial wrought magnesium alloys are proposed using servo presses. The influence of press ram motion on forgeabillity of magnesium alloy is examined at elevated temperatures by upsetting and die forging on a servo press. The forging limit of a wrought AZ31B (Mg-3% Al-1% Zn) magnesium specimen with decelerated ram motion control of the press is found to be 30% higher than the forging limit without press ram motion control. Since the flow stress curves of the wrought magnesium alloys exhibit work softening tendency, peak forging load tends to appear at an early stage of forging process. In order to reduce the peak forging load, a warm forging method for the magnesium alloys with consideration of their work softening characteristics is suggested using a servo press. Appropriate shape of the initial specimen is found to reduce the peak forging load by approximately 30% in the proposed forging method through the finite element analysis and experiment using the servo press. On the other hand, cold die forging of the magnesium alloy against counter punch pressure is conducted on a double axis servo press. By applying counter punch pressures of 100 - 200 MPa from die exit during forging, the critical punch stroke for cracking is improved by about 20% because the ductility increases under a high pressure.