Microstructure and mechanical properties of aluminum matrix composites reinforced with pre-oxidized β-Si3N4 whiskers

Aluminum matrix composites (AMCs) reinforced with pre-oxidized β-Si3N4 whiskers (β-Si3N4w) were fabricated by hot pressing method. An amorphous SiO2 layer was formed on the surface of β-Si3N4w aiming to enhance the interfacial bonding strength between aluminum and β-Si3N4. The interfacial structure showed that β-Si3N4w was well bonded with aluminum and no reaction products were formed near the interface. Effect of pre-oxidized β-Si3N4w on the mechanical properties of composites were investigated in detail. The results indicated that both the relative density and the mechanical behaviors of AMCs were increased. There was an optimum oxidation time for β-Si3N4w. The maximum promotion of ultimate tensile strength (UTS) was 25 MPa, 11% higher than the composites reinforced with as-prepared whiskers, when the oxidation time was 1 h and the whisker content was 5 vol%. However, long time oxidation would deteriorate the mechanical properties of β-Si3N4w, and thereby weaken the strengthening effect.