Effect of volume fraction on microstructure and mechanical properties of Si3N4/Al composites

Si3N4 particles reinforced aluminium matrix composites (Si3N4/Al) with different particle volume fractions (45%, 50%, and 55%) were fabricated by pressure infiltration method. The effects of Si3N4 volume fraction and T6 treatment on microstructure and mechanical properties of Si3N4/Al composite were investigated. The results show that Si3N4/Al composites are well infiltrated with good particles dispersion and no apparent porosity or significant casting defects are observed. High density of dislocations in Al matrix around Si3N4 particles is observed. The bending strength of Si3N4/Al composites decreases with an increase in Si3N4 volume fraction, and can be greatly improved by T6 treatment. Elastic modulus of composites increases linearly with Si3N4 volume fraction. At a lower Si3N4 volume fraction, more tearing ridge and dimples with elongation are observed. T6 heat treatment shows minor effect on the fracture surface of composite.