Numerical study of stress-strain state of AMG6 alloy during open-die forging

The article presents studies of the stress-strain and temperature-velocity states of the AMg6 alloy during free-die forging. Numerical experiments on free-die forging of samples with a diameter of 15.0; 20.0; 25.0 and 30.0 mm were carried out in the QForm program. During the experimental studies, the free-die forging speed was 0.1, 0.5, 1 and 5 mm/s and the workpiece temperature was 20, 130, 260 and 390 °C. The research results showed that the side surface of the sample is a zone of maximum average stresses, and the periphery of the contact surface of the sample with the die is a zone of minimum average stresses during free-die forging. The maximum values of the shear stress intensity are located at the periphery of the contact surface of the sample with the die. The stress state indicator σ/T, which characterizes the minimum plasticity of the material being processed, during free-die forging takes on its maximum values on the side face of the sample and does not change its position with a change in heating temperature. An increase in the temperature of the sample during free-die forging leads to a decrease in the average stresses and the intensity of the tangential stresses, but the patterns of distribution of their maximum and minimum values remain unchanged when the temperature of the sample changes. Increasing the free-die forging speed from 0.1 to 5 mm/s leads to a slight increase in stress intensity by 15-20 MPa. Deformation heating significantly depends on the free-die forging speed and the initial temperature of the sample. The maximum deformation heating is localized in the central part of the sample. The deformation rate during free-die forging at a rate of 5 mm/s does not exceed 1.1 s-1. The distribution of strain rates over the cross section is uneven. During the free-die forging process, first the maximum stresses arise in the center of the workpiece, then they increase and spread along the forging cross. When the degree of deformation is more than 50 %, the maximum values move to the periphery of the contact of the sample with the dies and remain there until the deformation is completed. Free-die forging forces are largely determined by the size of the sample, its heating temperature, hardening during cold deformation and slightly depend on the forging speed.