Preparation and mechanical properties of in situ submicron MgAl₂O₄p/6061Al composites from Al–Mg–SiO₂ system

Effect of the Stirring Velocity and the SiO2 Precursor Particles Feeding Rate on the Microstructure of the Al2O3/SiO2/Al Composites Prepared via Stir Casting Process

“…This is because the thicknesses of Al 2 O 3 layers produced by the in situ reaction of SiO 2 and Al are quite different. The morphology of the reinforcements in the aluminum matrix composite was not similar with the in situ prepared Al 2 O 3 /SiO 2 /Al composites as reported by Liu et al [ 25 ] While adding the Mg element in aluminum, the reaction among the SiO 2 , Al and Mg would result in the formation of the reinforcements (MgAl 2 O 4 ) with “Chinese‐script”‐type morphology, but not forming the “shell–core” Al 2 O 3 /SiO 2 morphology. As far as the reaction of SiO 2 and molten aluminum without any alloy elements, the reaction rate of Al 2 O 3 was relatively low.…”

“…To generate the reinforcements in the aluminum matrix, the in situ method requires the precursors bulk (usually fabricated by cold pressing the mixture of SiO 2 particles and the binder) should be prepared beforehand. [24,25] However, if the vol% of precursor particles in the bulk is relatively high or the diameter of the particles is small, the particles would tend to agglomerate in the melts. The ex situ technique, by incorporating the precursor particles into the stirring vortex of the melts, might be more effective to prevent the agglomeration of particles under the stir casting preparation.…”