M. Nagumo et al., Deformation-induced defects controlling fracture toughness of steel revealed by tritium desorption behaviors, ACT MATER, 48(4), 2000, pp. 943-951
Defects induced by plastic deformation have been revealed by means of room
temperature desorption and thermal desorption spectroscopy of tritium with
regards to the ductile crack growth resistance and brittle fracture initiat
ion in steels in the ductile-to-brittle transition region. Tritium, as a pr
obe for detecting defects, was introduced into non-deformed or deformed sam
ples. Three steels, the microstructures of which are characterized by the c
onstrains factor for slip extension, were employed. The residual tritium in
a specimen after three days at room temperature increased to the extent co
rresponding to the constraint factors when plastic deformation was applied.
The thermally desorbed tritium, with a peak desorption rate around 150 deg
rees C, also increased according to the constraint factors. Referring to th
e previous analysis of the R-curves, the constraint for the extension of sl
ip across grain boundaries is shown to control both the ductile crack growt
h resistance and the brittle fracture initiation through the deformation mi
crostructures that evolve vacancy clusters or microvoids. (C) 2000 Acta Met
allurgica Inc. Published by Elsevier Science Ltd All rights reserved.