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High‐Temperature Fracture Toughness of Duplex Microstructures
Author(s) -
French Jonathan D.,
Chan Helen M.,
Harmer Martin P.,
Miller Gary A.
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb07880.x
Subject(s) - indentation , materials science , fracture toughness , composite material , microstructure , plasticity , ceramic , toughness , duplex (building) , cubic zirconia , chemistry , dna , biochemistry
The temperature dependence of the fracture toughness of ceramics exhibiting duplex microstructures was studied relative to their single‐phase constituents using two test methods: bend testing of chevron‐notched beams, and the indentation‐crack‐length technique. The two materials systems studied were Al 2 O 3 : c ‐ZrO 2 (Y) and A1 2 O 3 :Y 3 A1 S O 12 (YAG), and the testing temperature ranged from room temperature to 1200°C. The study showed that in both systems the duplex materials showed higher toughness values than their single‐phase constituents above 800°C. This result was attributed to the contribution of low‐energy interphase boundaries to the overall composite toughness. Indentation crack length measurements gave toughness values and trends comparable to those determined by the chevronnotched beam method. By comparing the results of the two test methods it was possible to demonstrate that the indentation calibration constant (ξ) shows no significant temperature or material dependence. For the zirconia‐containing materials, however, indentation at elevated temperatures is accompanied by significant localized plasticity, which suppressed the radial cracking. Under such conditions, some caution is warranted, since localized plasticity can lead to an overestimation of the fracture toughness.