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

Porous aluminum nitride (AIN) preform was formed by sintering in N-2 at 160 0 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 A IN composition in AIN Al composite increased from 51.2 to 70.0% when the pr essing 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 s trength increased from 328 to 490 MPa. and the compressive strength increas ed 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 transgranul ar fracture within larger AIN grains. Three crack growth paths along (1) Al /Al interface, (2) AlN/AlN interface, and (3) AlN/Al interface were observe d in the AlN/Al composites. The fracture toughness of the squeeze casting A lN/Al composites was between 14.5, and 15.7 MPa mi 2. No obvious trend betw een the fracture toughness and the composition of the composite has been ob served. However. the ductility of the composite decreased with the increase of AIN content. (C) 2001 Elsevier Science Ltd. All rights reserved.