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Brittle–Ductile Transition and Dislocation Mobility in Sapphire
Author(s) -
Kim HyungSun,
Roberts Steve
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.tb04555.x
Subject(s) - sapphire , materials science , strain rate , brittleness , dislocation , composite material , slip (aerodynamics) , activation energy , stress (linguistics) , strain (injury) , crystallography , thermodynamics , optics , chemistry , laser , physics , organic chemistry , medicine , linguistics , philosophy
The brittle‐to‐ductile transition (BDT) of Precracked sapphire in four‐point bending was studied as a function of orientation and strain rate from room temperature to 1500°C. Plastic deformatiom of sapphire occurs via basal and prismatic slip during loading at high temperature (above 1030–1100°C, depending on orientation). The BDT temperature, T c , varies with strain rate and crystallographic orientation of the fracture plane. The activation, derived from the strain rate variation of T c , is approximately energy of the process controllingh the BDT in sapphire, derived from the strain rate variation of T c is sapproximately 3.2 eV, close to that for dislocation glide. In one specimen orientation, “warm‐prestressing” increases the room‐temperature fracture stress.