Mechanical properties of Si₃N₄/AIN-Al composites prepared by pressure-free infiltration

The Si₃N₄/AlN-Al composites with different ceramic contents were successfully prepared in N₂ atmosphere by optimized pressure-free infiltration process at 950 °C for four hours. The flexural strength, compressive strength, fracture toughness and hardness of the prepared composites were measured to understand the effects of ceramic content on mechanical properties and fracture morphology of composites. The results reveal that with the increase of Si₃N₄ content in the performs from 30. 2% to 60.6% (in volumetric fraction), the compressive strength, flexural strength and hardness of the composites can be increased from 620 MPa to 1 728 MPa, from 429.8 MPa to 672.4 MPa and from 55 to 83, respectively, with the decrease of fracture toughness from 10.55 MPa · m^1/2 to 2.26 MPa · m^1/2. The crack in the Si₃N₄/AlN-Al composites is formed at three types of zones including remained coarse Si₃N₄ particles, loosen sections and coarse Mg₂Si phase.