The mechanical properties of AlN/Al composites manufactured by squeeze casting

Porous aluminum nitride (AIN) preform was formed by sintering in N-2 at 1600 degreesC for 1 h. The molten pure Al was infiltrated into the preform to make AlN/Al composite with different compositions by squeeze casting. The AIN composition in AIN Al composite increased from 51.2 to 70.0% when the pressing pressures of AIN preforms increased from 10 to 60 MPa, respectively. The hardness of the composite increased from 93 to 145 H-v. the fracture strength increased from 328 to 490 MPa. and the compressive strength increased from 210 to 340 MPa for the corresponding composites. The fracture modes in AlN/Al composites included (1) ductile neck fracture in Al, (2) brittle intergranular fracture between smaller AIN grains, (3) brittle transgranular fracture within larger AIN grains. Three crack growth paths along (1) Al/Al interface, (2) AlN/AlN interface, and (3) AlN/Al interface were observed in the AlN/Al composites. The fracture toughness of the squeeze casting AlN/Al composites was between 14.5, and 15.7 MPa mi 2. No obvious trend between the fracture toughness and the composition of the composite has been observed. However. the ductility of the composite decreased with the increase of AIN content. (C) 2001 Elsevier Science Ltd. All rights reserved.