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Dislocation Activity, Stable Crack Motion, and the Warm‐Prestressing Effect in Magnesium Oxide
Author(s) -
Booth Andrew S.,
Roberts Steven G.
Publication year - 1994
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.1151-2916.1994.tb09743.x
Subject(s) - materials science , dislocation , composite material , shielding effect , fracture toughness , magnesium , electromagnetic shielding , fracture (geology) , oxide , metallurgy
Four‐point bend tests were performed on precracked single‐crystal MgO specimens at different temperatures and strain rates. A large amount of stable crack growth before fracture occurred; etching revealed dislocations in the crack advance region. We believe that dislocation sources near the crack tip emit loops, producing shielding and antishielding dislocations; the latter promote crack advance by a repeated microcleavage mechanism. “Warm‐prestressing” experiments, which improve the room‐temperature fracture toughness by dislocation shielding, were performed. There was a prestress below which no “warmprestressing effect” (WPSE) was exhibited and the magnitude of the WPSE increased with increasing prestressing temperature.