SYMPOSIA PAPER Published: 01 January 1997

On the Requirement for a Sharp Notch or Precrack to Cause Environmentally Assisted Crack Initiation in β-Titanium Alloys Exposed to Aqueous Chloride Environments


The requirement of a sharp notch or precrack to cause environmental crack initiation of metastable β-titanium alloys exposed to 0.6 M NaCl has been observed. The causal relationship has not been thoroughly examined, however. This paper seeks to explain the sharp notch requirement by examining notch acuity effects on a variety of parameters that affect HEAC susceptibility. These include the effects of a sharp notch on cation accumulation - hydrolysis - acidification, potential drop in solution and resulting hydrogen production, and localization of dynamic strain. It is shown that solution resistance down a sharp crack is two orders of magnitude larger for a fatigue precracked compact tension specimen than for a smooth bar. The potential drop down a sharp crack is severe enough to enable hydrogen production even when the applied potential is more positive than the reversible potential for hydrogen production. It also shown that a fatigue precrack results in an acidified crack tip chemistry (approximately pH 1) which is deleterious to HEAC resistance. The effects of a sharp notch on the interplay of mechanics, film rupture and hydrogen uptake are also examined. It is shown that the slip behavior at a sharp crack tip promotes localized film rupture and localized hydrogen uptake. Localization of hydrogen uptake may be critical for HEAC susceptibility in light of the large hydrogen concentration required to cause crack initiation (ca. 1000 wt. ppm) and the lack of significant hydrogen uptake on filmed surfaces.

Author Information

Kolman, DG
Los Alamos National Laboratory, Los Alamos, NM
Scully, JR
University of Virginia, Charlottesville, VA
Price: $25.00
Contact Sales
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Developed by Committee: G01
Pages: 61–73
DOI: 10.1520/STP19953S
ISBN-EB: 978-0-8031-5357-8
ISBN-13: 978-0-8031-2408-0