Effect of matrix temperature and powder size on the infiltration height of SiO2 -reinforced Al 7075 matrix composites produced by vacuum infiltration

Abstract

In this study, Al-MgO metal matrix composites (MMC) were produced with 5 %, 10 % and 15 % reinforcement-volume (R-V) ratios by the melt stirring method. In the production of composites 99.5 % pure Al was used as the matrix and MgO powders with the particle size of -105 mu m were used as the reinforcement. For every R-V ratio; stirring was made at 500 rev/min at 750 degrees C liquid matrix temperature for 4 minutes and the samples were cooled under norrnal atmosphere. Then hardness and fracture strengths of the samples were determined and their microstructures were evaluated by using Scanning Electron Microscope (SEM). In general, it was observed that the reinforcement exhibited a homogeneous distribution in horizontal direction. But there is a slight inhomogeneity in vertical direction. It was determined that the increase in the R-V ratio increased the porosity and also the hardness. As for the fracture strength, the highest strength was obtained with the 5 % MgO reinforced sample.