The work hardening and softening behavior of spherical Ti_p/Mg-5Zn-0.3Ca composite

To obtain the Ti_p with different aspect ratios, the Ti_p/Mg-5Zn-0.3Ca composite prepared by semi-solid stir casting was subjected to extrusion at 220℃, 180℃, and 140℃, respectively. Then, the effect of the Ti_p’s aspect ratio on the microstructure, mechanical properties, work hardening and softening behaviors of Ti_p/Mg-5Zn-0.3Ca composites was investigated. The results indicated that the Ti_p could be elongated obviously after low-temperature extrusion, and the aspect ratio of which would reach to 13.7:1 as the extrusion temperature deceased to 140℃. Then the “Ti/Mg” layer-like structure was formed in the Ti_p/Mg-5Zn-0.3Ca composite. Accompanied with the elongation of Ti_p, the dynamic recrystallized grains and dynamic precipitates were both refined significantly, however, the dynamic recrystallization rate changed a little. The elongated Ti_p endowed the Ti_p/Mg-5Zn-0.3Ca composites with better matching of strength and toughness without the sacrifice of elongation and bending strain. Both the work hardening rate and softening rate of Ti_p/Mg-5Zn-0.3Ca composites increased with the increasing aspect ratio of Ti_p. The formation of “Ti/Mg” layer-like structure contributed to the redistribution of strain from large aggregations to a network-like distribution, which effectively suppresses the initiation and propagation of micro-cracks, thus enhancing the plasticity of the Ti_p/Mg-5Zn-0.3Ca composites.