Effect of Tip Content on the Work Hardening and Softening Behavior of Mg-Zn-Ca Alloy

The -Ti-p/ ZX60 composites with different -Ti-p contents were prepared by semi- solid stirring casting. After extrusion, the microstructure, work hardening and softening behavior of the -Ti-p/ZX60 composites were analyzed compared with the ZX60 (Mg-6Zn-0.2Ca) alloy. The results showed that the addition of -Ti-p could not only promote the nucleation of dynamic recrystallized (DRXed) grains, but also be propitious to the refinement of DRXed grains. With increasing -Ti-p content, the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed grains. As the -Ti-p content increased to 15 vol.%, the average size and volume fraction of DRXed grains reached to similar to 0.32 mu m and 93.2%, respectively. Besides, both the strength and elongation were improved by the addition of -Ti-p. With increasing content of -Ti-p, a substantial increase in the strength was achieved with little change in the elongation. However, the elongation decreased sharply when the -Ti-p content further increased to 15 vol.%. The addition of -Ti-p led to an increase in the work hardening rate, which gradually increased with increasing -Ti-p content. However, the softening rate did not demonstrate the same tendency with increasing -Ti-p content. Unlike the conventional ceramic particles, the -Ti-p can be deformed in coordination with the matrix alloy, which imparted a higher softening rate to the matrix alloy. Even though the softening rate improved as the -Ti-p content increased from 5 to 10 vol.%, it dropped deeply as the -Ti-p content increased to 15 vol.% owing to the fracture of -Ti-p during extrusion.