Dj. Simbi et Jc. Scully, FRACTURE MORPHOLOGIES EXHIBITED BY COMMERCIALLY PURE TITANIUM WHEN STRAINED TO FAILURE WHILE IN CONTACT WITH CHLORIDE-CONTAINING ENVIRONMENTS, Corrosion science, 35(1-4), 1993, pp. 489-497
The combined effects of oxygen, nitrogen and carbon, expressed as an o
xygen equivalent {O}, and, also, the influence of residual iron conten
t, on the stress-corrosion behaviour of commercially-pure titanium whe
n strained slowly to failure while in contact with sea water have been
investigated. The fracture morphologies exhibited comprised a mixture
of cleaved facets and areas of low-energy ductile rupture of the alph
a phase, referred to as flutes or flutings. An increase in the {O} con
tent resulted in an increase in the number of cleaved facets and in th
e associated continuity of the observed cleavage fracture. The cleaved
facets were not exactly smooth surfaces, but were comprised of facets
separated by small steps. The latter have been associated with slight
differences in orientation between the cleavage planes and the crack-
propagation plane. Flutings which were well developed in low residual
iron-containing titanium allowed the joining of two cleavage planes in
two different grains sharing a common boundary. However, when two cle
avage planes were unable to join by a single-fluted system, a two-flut
ed system which met at a grain boundary became operative. Increased re
sidual iron levels were found to eliminate stress-corrosion susceptibi
lity; hence, the non-occurrence of cleavage fracture in low {O} titani
um. In high {O}-containing material, cleavage fracture was observed, b
ut with a much reduced continuity of the cleavage fracture.