Effect of extrusion on the microstructure and mechanical properties of a low-alloyed Mg–2Zn–0.8Sr–0.2Ca matrix composite reinforced by TiC nano-particles

A low-alloyed Mg–2Zn–0.8Sr–0.2Ca matrix composite reinforced by TiC nano-particles was successfully prepared by semi-solid stirring under the assistance of ultrasonic, and then the as-cast composite was hot extruded. The results indicated that the volume fraction of dynamical recrystallization and the recrystallized grain size have a certain decline at lower extrusion temperature or rate. The finest grain size of ~0.30 µm is obtained in the sample extruded at 200°C and 0.1 mm/s. The as-extruded sample displays a strong basal texture intensity, and the basal texture intensity increases to 5.937 mud while the extrusion temperature increases from 200 to 240°C. The ultra-high mechanical properties (ultimate tensile strength of 480.2 MPa, yield strength of 462 MPa) are obtained after extrusion at 200°C with a rate of 0.1 mm/s. Among all strengthening mechanisms for the present composite, the grain refinement contributes the most to the increase in strength. A mixture of cleavage facets and dimples were observed in the fracture surfaces of three as-extruded nanocomposites, which explain a mix of brittle-ductile fracture way of the samples.