LAUSR

Abstract In the present work, Al 2 O 3 -GdAlO 3 oxide nanopowders with eutectic composition of 77:23 (in molar ratio) were prepared via a chemical co-precipitation method. α-SiC particles were then incorporated with different volume fractions of 10, 15 and 20 vol% into the oxide powders. Al 2 O 3 -GdAlO 3 –SiC ceramics were hot-pressed at different sintering temperatures to obtain fully densified bulk ceramics. The as-sintered composites consist mainly of α-Al 2 O 3 , GdAlO 3 and α-SiC phases, and exhibit a dense and uniform microstructure. The GdAlO 3 grains are entangled with α-Al 2 O 3 grains as indicated by SEM observations. SiC nanoparticles are found within the interior of both α-Al 2 O 3 and GdAlO 3 grains or at the interfaces between entangled α-Al 2 O 3 and GdAlO 3 . With increasing the SiC content from 10 to 20 vol%, the high-temperature flexural strength of Al 2 O 3 -GdAlO 3 -SiC ceramics increases from 567 to 616 MPa, and the Vickers hardness increases from 17.5 to 19.5 GPa, while the fracture toughness of Al 2 O 3 -GdAlO 3 -SiC ceramics increases from 8.20 to 9.28 MPa m 1/2 , which is significantly improved with respect to that (7.5 MPa m 1/2 ) of unmodified Al 2 O 3 -GdAlO 3 ceramic. The toughening mechanisms of Al 2 O 3 -GdAlO 3 -SiC ceramics are attributed to crack deflection, pinning and bridging, and bifurcation due to the presence of SiC nanophases observed from the indentation.