Fracture Mechanisms of a Coarse‐Grained, Transparent MgAl2O4at Elevated Temperatures
作者:
Kenneth W. White,
Girish P. Kelkar,
期刊:
Journal of the American Ceramic Society
(WILEY Available online 1992)
卷期:
Volume 75,
issue 12
页码: 3440-3444
ISSN:0002-7820
年代: 1992
DOI:10.1111/j.1151-2916.1992.tb04446.x
出版商: Blackwell Publishing Ltd
数据来源: WILEY
摘要:
The fracture of a transparent, large‐grain‐sized MgAl2O4spinel has been studied through temperatures of 1400°C. Fracture toughness values, falling between about 1.3 and 2.3 MPa.m12;1/2, behaved sigmoidally with temperature, with a lower shelf transition appearing near 800°C. RisingR‐curves, displaying a run‐arrest character, were found at both the lowest and the highest temperatures, while only minimal values of dKR/dΔawere produced at intermediate temperatures of 800°C. This fracture character is ascribed largely to finite concentrations of a residual LiF pressing aid identified on the fracture surface, while additional influences associated with the lower shelf region at the highest temperatures may include the increased fraction of intergranular crack path and the onset of plasticity. This cubic monolithic ceramic displayed strong nonlinear fracture behavior in both temperature regimes. In both cases the fracture character is linked directly to an active toughening mechanism in the wake region, which depends upon crack fa
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