Abstract: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.

Key words: Si₃N₄/Al composite; microstructure; bending properties; fracture surface