Effects of heat treatment before extrusion on dynamic recrystallization behavior, texture and mechanical properties of as-extruded Mg-Gd-Y-Zn-Zr alloy

The effects of heat treatment before extrusion on the dynamic recrystallization (DRX) behavior, texture, and mechanical properties of the extruded Mg-9.8Gd-3.5Y-2.0Zn-0.4Zr (wt. %) alloy were comparatively investigated in this work. A large number of dendritic microstructures in as-homogenized alloy and intergranular block-shaped LPSO phases in as-aged alloy were found to promote the operation of particle-stimulated nucleation (PSN) and discontinuous dynamic recrystallization (DDRX) mechanisms, which further accelerate growth of dynamic recrystallized grains due to the lack of solute drag and dynamic precipitation. Also, we determined the nucleation of dynamic recrystallization affects little to the formation of abnormal texture, whereas the shear stress results from the flow velocity gradient and the pyramidal-2 slip during the growth of the dynamic recrystallized grains leading the formation of abnormal texture. However, the solution treatment before extru-sion could effectively eliminate the dendritic microstructures and increase the solid solubility of the matrix, which would facilitate the occurrence of continuous dynamic recrystallization (CDRX) and dynamic precipitation during the hot extrusion process. Meanwhile, CDRX and dynamic precipitation co-contribute to the formation of a bimodal microstructure that composed of coarse deformed grains with basal orientation and fine dynamic recrystallized grains with random orientation. The observed bimodal microstructure, fine dynamic pre-cipitations, strong fiber texture, and substructure thus well explained the improved strength and elongation of samples extruded with the solution treated materials.

Automated summary

The effects of heat treatment on the dynamic recrystallization behavior, texture, and mechanical properties of a magnesium alloy were investigated. It was found that heat treatment can eliminate microstructures and increase the solid solubility, leading to the occurrence of continuous dynamic recrystallization and dynamic precipitation, which improve the alloy's performance.