Compression Behaviour of Semi-closed Die Forged AZ80 Extrusion

Warm forging to near final product geometry shows promising benefits in terms of microstructure refinement and texture modification. In the present study, Semi-closed die forging was performed on extruded AZ80 magnesium alloy at a forging temperature of 400 °C and various forging ram speeds. Compression tests were performed to investigate the influence of forging at various deformation rates on the performance of extruded AZ80 magnesium alloy. The microstructural analysis showed that the extruded AZ80 possesses a grain structure typical in wrought magnesium alloys, with sharp basal texture. In contrast, the forged samples had a recrystallized microstructures and a spatially varying textures and crystal orientations resulting from the complex flow behaviour within the closed die forging. Furthermore, once forged, a significant increase in the material isotropy, homogeneity as well as failure elongation were observed. An increase in UCS of 9% was observed in the forging direction, while the UCS in the extrusion direction was similar to that before forging. The changes in UCS can be attributed to both the refined grain microstructure and crystal reorientation. Successful microstructure recrystallization occurs for strain rates which traverse several orders of magnitude, and in general, UCS isotropy increases with increasing strain rate. It is believed that forging cause’s grain refinement and texture modification which act to enhance the mechanical performance (UCS, fracture strain and superficial hardness) for the forging conditions investigated in this study.