3D processing maps of cast Mg-8Gd-3Y alloy at high strain rates and their application in plane strain forging

The stress-strain curves of cast Mg-8Gd-3Y (GW83) alloy at the high strain rates ranging from 0.1 to 1.5 s(-1) were obtained by isothermal compression tests. In order to exhibit the hot formability related to material itself, the three-dimensional (3D) processing maps of GW83 alloy were constructed on the basis of hot compression experimental data and dynamic material model (DMM). The 3D processing maps show that the material at high strain rates mostly suffers flow instability, and safety deformation occurs only in a narrow high-temperature domain. The formable processing region is concentrated within the temperature range of 410-440 degrees C and strain rate range of 0.20-0.73 s(-1). By means of user subroutines, the 3D processing maps were integrated into the finite element (FE) software Deform-3D, and the formability of GW83 alloy during the isothermal plane strain forging (PSF) process under four different parameters was predicted. The simulation results indicate that the material possesses good formability under the three parameters of safety region (410 degrees C/0.4 s(-1), 440 degrees C/0.3 s(-1), and 440 degrees C/0.4 s(-1)), and flow instability occurs under the parameters of instability region (400 degrees C/0.8 s(-1)). Combined with microstructure observation, the accuracy of the simulation results and 3D processing maps was verified via the PSF experiments under the same process parameters as the simulated conditions.