Microstructure and impact behavior of Al/SiC p composites fabricated by pressureless infiltration with different types of SiC p

Abstract

The effect of the type of SiC p (green or black), Mg content in the aluminum alloy and holding time on the microstructure and impact strength of Al/SiC p composites fabricated by pressureless infiltration was investigated. Preforms of SiC p in the form of rectangular bars (10 cm × 1 cm × 1 cm) were infiltrated at 1150 °C in argon → nitrogen atmosphere for 45 and 60 min utilizing two aluminum alloys (Al–6Mg–11Si and Al–9Mg–11Si) (wt.%). Results show that the presence of a higher amount of black SiC has a beneficial effect in the composites microstructure because it prevents formation of the unwanted Al 4C 3 phase. The impact strength is enhanced when the Mg content varies from 6 to 9 wt.% and decreases when the Al 4C 3 phase is present. Moreover, a higher amount of Mg in the alloy is reflected in a lower residual porosity and consequently in a higher impact strength in the composites.