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Porous aluminum nitride (AlN) preform was formed by sintering in N 2 at 1600°C for 1 h. The molten pure Al was infiltrated into the preform to make AlN/Al composite with different compositions by squeeze casting. The AlN composition in AlN/Al composite increased from 51.2 to 70.0% when the pressing pressures of AlN 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 AlN grains, (3) brittle transgranular fracture within larger AlN 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 m 1/2 . 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 AlN content. |
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