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Influence of microstructural variation on fracture toughness of LPS-SiC ceramics

2004; Elsevier BV; Volume: 22; Issue: 4-5 Linguagem: Inglês

10.1016/j.ijrmhm.2004.05.001

0263-4368

Kurt Strecker, S. Ribeiro, R. Oberacker, Michael J. Hoffmann,

Aluminum Alloys Composites Properties

The influence of microstructural variations obtained by different powder compositions and sintering times on the fracture toughness of liquid phase sintered (LPS)-SiC has been investigated. SiC ceramics were obtained by normal sintering in flowing nitrogen at 2080 °C for 1 h using 10 wt% of AlN and Y2O3 mixtures as additives, at molar ratios of 80:20 and 40:60, respectively. In order to modify the microstructures some samples of each composition were further heat-treated at 2000 °C for 4 h to promote grain growth. It has been found that the AlN rich composition resulted in a microstructure with more elongated, platelet like grains and therefore increased fracture toughness. Grain growth resulted also in higher fracture toughness especially because the mechanism of crack-deflection is more pronounced. AlN rich samples sintered at 2080 °C for 1 h and heat-treated at 2000 °C for 4 h showed fracture toughness of 6.7 MPam (determined by the SENVB method).