On the structure-properties relationship of amorphous and crystalline silica nanoparticles reinforced magnesium matrix nanocomposites

Abstract

In this study, the structure-properties relationship of magnesium matrix nanocomposites was studied. Using an accumulative extrusion (AE) process, the matrix was reinforced by adding 0.25, 0.5 and 1 wt% crystalline and amorphous silica nanoparticles separately. The mechanical behavior of nanocomposite strips was investigated by hardness and uniaxial compression tests. The results indicated that the Mg/0.5%SiO2-Am had the best room temperature compressive properties. An increase of 28.5% in compressive yield strength after extrusion and 235% after annealing was measured. Ultimate compressive strength (UCS) was increased by 20% without reduction in the nanocomposite ductility compared to the pure magnesium strip. FESEM and OM were used for microstructural analysis and revealed no visible cracks or distinct defects between magnesium layers after AE passes. It is found from the EDS analysis that the reinforcement distribution after the AE process was uniform with few agglomerates. Texture analysis using X-ray diffraction and EBSD after the AE process for samples reinforced with 0.5 wt% of amorphous and crystalline silica nanoparticles indicated a negligible difference in the basal plane orientation of the monolithic and nanocomposite magnesium strips after the AE process along extrusion direction. On the other hand, increasing the basal plane peak intensity after annealing for the sample reinforced with amorphous silica compared to the sample reinforced with crystalline silica indicated a weakening of basal texture. Furthermore, the EBSD analysis showed that amorphous silica nanoparticles are more effective than crystalline silica in grain refinement.