Mechanical Properties and Work Hardening Behavior of Tip/Mg-Gd-Y-Zn Composites

In this work, Ti_p/Mg-7Gd-2Y-3Zn (Ti_p/GWZ723) composites with various Ti_p sizes (~ 10 μm, ~ 20 μm and ~ 35 μm) were fabricated using semi-solid stirring casting method, the composites were subjected to hot extrusion, and the influence of Ti_p size on long-period stacking ordered (LPSO) phase, dynamic recrystallization (DRX), mechanical properties, and work hardening behavior of the Ti_p/GWZ723 composites was investigated. The results indicate that with the increase in Ti_p size, the grain size of the as-cast Ti_p/GWZ723 composites increases, and the lamellar 14H LPSO phase precipitates within the matrix after homogenization treatment. With the increase in Ti_p size, the reduction in the Ti_p surface area leads to a decrease in surface energy. Consequently, the enrichment of RE element is reduced, which facilitates the formation of the 14H LPSO phase. Moreover, the layer spacing of the 14H LPSO phase decreases. Particle deformation zone (PDZ) is formed around the Ti_p after extrusion, promoting the nucleation of DRX. The PDZ size increases with the increase in the Ti_p size. Nevertheless, the elongation of the Ti_p releases stress and reduces the PDZ size. Simultaneously, the 14H LPSO phase with a small interlayer spacing inhibits the non-basal slip, and the volume fraction of DRX (V_DRX) decreases with the increase in the Ti_p size. With the increase in Ti_p size, the refined grain size and the 14H LPSO phase with smaller interlayer spacing contribute to enhancing the work hardening rate and dynamic recovery rate of the Ti_p/GWZ723 composites. The Ti_p/Mg laminar-like interface formed in the Ti_p/GWZ723 composites can alleviate local stress concentration and inhibit the initiation and propagation of cracks.