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Residual Displacement Effects During Crack Propagation in High‐Toughness Magnesia‐Partially‐Stabilized Zirconia
Author(s) -
Steinbrech Rolf W.,
Inghels Eric,
Heuer Arthur H.
Publication year - 1990
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.1151-2916.1990.tb05261.x
Subject(s) - materials science , residual stress , toughness , fracture mechanics , crack growth resistance curve , composite material , fracture toughness , diffusionless transformation , residual , crack tip opening displacement , cubic zirconia , crack closure , plasticity , displacement (psychology) , tetragonal crystal system , martensite , microstructure , ceramic , crystallography , mathematics , crystal structure , psychology , algorithm , psychotherapist , chemistry
Fracture mechanics testing of high‐toughness MgO‐partially‐stabilized ZrO 2 (Mg‐PSZ) using the double‐cantilever‐beam (DCB) geometry leads to large residual displacements in specimens unloaded after partial crack propagation. The residual displacements are due to transformation “plasticity” (the martensitic transformation of tetragonal precipitates within the PSZ) and increase linearly with increasing crack extension; the residual displacements can be eliminated by removing portions of the crack “wake” by machining (renotching). Surprisingly, some residual displacement survived after removal of more than 500 μm from the crack surfaces, implying that the transformation zone was >250 μm in extent. Furthermore, the results suggest subcritical transformation in the zone. Annealing eliminates the residual displacements, due to retransformation of transformed particles. Retransformation began at 500°C and was not completed until 900°C. The residual displacements depend on specimen and crack geometry; thus a geometry dependence is inherent in resistance ( R ) curves that are derived from load‐displacement‐crack extension data.