Multi-directional forging of large-scale Mg-9Gd-3Y-2Zn-0.5Zr alloy guided by 3D processing maps and finite element analysis

The three-dimensional (3D) processing maps of cast Mg-9.0Gd-3.0Y-2.0Zn-0.5Zr alloy were established based on isothermal compression tests and dynamic material model (DMM). The stable and power-efficient forming domains were determined by considering both the instability and power dissipation efficiency maps. Multi-directional forging (MDF) was then simulated by employing finite element (FE) analysis in the Deform-3D software, using the 3D power dissipation efficiency maps as input. The optimal forging parameters were thus obtained for a large-scale ingot with 430 mm in diameter and 440 mm in height, i.e., a forging temperature of 450 °C and forging speed of 10 mm/s. Finally, a Mg-9.0Gd-3.0Y-2.0Zn-0.5Zr cake-shaped forged part with 900 mm in diameter and 100 mm in height was produced. After T6-heat treatment, the edge and center of the forged part exhibit homogeneous microstructure and relatively consistent properties, with the tensile strength, yield strength, and elongation being about 400 MPa, 320 MPa, and 14.0%, respectively. Using transmission electron microscopy, the main strengthening phases were revealed to be the dense nano-scale β′ phases that are uniformly distributed inside the material.