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~0.30μm is obtained in the sample extruded at 200℃ 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℃.The ultra-high mechanical properties(ultimate tensile strength of 480.2 MPa,yield strength of 462 MPa)are obtained after extrusion at 200℃ 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.

Ameliorating the Strength-Modulus Synergy in GNPs Reinforced Mg-Zn-Zr Composites via Multidirectional Forging and Hot Extrusion Deformation

The integration of lightweight and high-modulus magnesium-based materials is becoming increasingly valued as structural materials due to the complexity and intelligence of industrial products like automobiles and electronics.In this study,the graphene nanoplatelets(GNPs)/Mg-Zn-Zr composites with 0.5 wt%GNPs were successfully prepared by the combination of multidirectional forging(MDF)and hot extrusion(Ex).The newly-developed composites after multi-step deformation possessed excellent strength and modulus,with a tensile strength exceeding 375 MPa and an elastic modulus reaching 54 GPa.The results revealed that the stripping and thinning of GNPs bands parallel to the extrusion direction occurred after MDF+Ex,which promoted the dynamic recrystallization and the formation of numerous fine grains.The significant improvement in comprehensive mechanical performances of the composites could be primarily ascribed to the refinement of grain size caused by the optimized distribution of GNPs,and efficient load transfer facilitated by the tight interface.