Study On Microstructure And Rheological Behavior Of In-stu Mg₂Si/AM60 Composites

Magnesium matrix composites have been widely used in spaceflight, mechanical electron, automobile manufacture etc. because of their low density, high specific strength and rigidity and good damping capacity.Mg₂Si/Mg composites were prepared by in-situ reactive synthesis technique in this essay. The effects of Si content on the microstructure and mechanical properties of Mg₂Si/Mg composites were systemically studied, and the modifying effect of Sb mischmetal on Mg₂Si phase in the composites was also studied.The results show that, with the increase of Si content, the amount of Mg₂Si in the solidified samples increases, and its shape becomes more full Chinese script. The tensile strength of 3% Si content was up to 181.7MPa which was more about 14.9% than that of the matrix. However, it would decrease while Si was increased continuously. When 0.8 wt. % Sb was added into the alloys, the shape of Mg₂Si could be transformed from the Chinese script into uniformly dispersed particles. Therefore, Mg₂Si/Mg composites with more desirable microstructure can be obtained.Semi-Solid processing has been attracting considerable interest for its well newly net forming, lower energy consumption and low pollution. Combined semi-solid processing and in-situ reactive synthesis technique, the semi-solid Mg₂Si/Mg slurry was isothermally stirred to study the effect of processing parameters on the rheological behavior and microstructure by the self-made mechanical stirring equipment. Semisolid rheological forming and the microstructure evolution rule of Mg matrix composites were discussed in this paper.The results show that, the microstructure of composites changed gradually from dendrite to rose-shaped, finally to be non-dendrite or spheroid-shaped as the increasing of shearing rate and shearing time. The apparent viscosity increased with increasing of Si content and solid fraction, while decreased with the increasing of shearing rate and shearing time. However, the apparent would not reduce after shearing over 300s but went to be a stable value.