Effect of die angle and temperature on metal flow and extrusion load in hot extrusion of a novel Mg-Zn-Ca alloy

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This work examines the extrudability of a novel bio-compatible Mg-Zn-Ca alloy in the hot working temperature range of 300°C to 400°C using conical dies with angles of 30°, 60°, and 90°. The effects of die angle and temperature on metal flow and extrusion load were analyzed using finite element simulations in Qform software. A flow model was developed to describe the alloy’s behaviour, and statistical parameters (R, R2, and % AARE) confirmed the suitability of the modified Johnson-Cook model. The determined model coefficients were used in the simulations. Predicted extrusion loads were validated through hot extrusion experiments using a 100-ton double-action hydraulic press. The influence of extrusion temperature and die angle on microstructure and hardness was also investigated. More homogeneous metal flow was observed with a 60° die angle. Stress, strain, and strain rate distribution showed more severe deformation near the billet surface than at the centre under all conditions. Peak load was higher at 300°C than at 350°C for all die angles, with 60° minimising the load. Predicted load agreed well with experiments, with maximum differences of 5.6 % and 13.8 % at 300°C and 350°C, respectively. Extrusion at 400°C caused surface cracking, indicating a suitabletemperature range of 300–350°C. A significant grain refinement (~80%) was observed after the extrusion process. Hardness measurements show higher surface hardness, reaching 70.5 HV at 300°C with a 90° die angle, which were consistent with finite element simulations.