Part 2. Metallurgical factors governing the H-assisted intergranular cracking of peak-aged Ti-3Al-8V-6Cr-4Mo-4Zr (Beta-C)

Journal Article · Sat Jan 01 00:00:00 EST 2000 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-000-0055-9· OSTI ID:20014047

Gaudett, M A; Scully, J R

A previous study (Part 1) showed that the solution-treated and aged (STA) (i.e., peak-aged) condition of Beta-C Ti, ({sigma}{sub 0.2 pct y} = 865 MPa), as measured by reductions in the fracture initiation stress with predissolved H content and the introduction of an intergranular (IG) fracture mode. It was also shown that yield-strength elevation and the subsequent enhancement in the local hydrostatic stresses within the notch root are not the controlling factors in the H-assisted IG fracture initiation of the STA condition. Previous work (Part 1) implicates a microstructural feature or condition associated with the 500 C aging treating. In this study, it is shown that localized internal hydride precipitation at the grain boundaries or alpha beta interfaces was not detected by a variety of experimental methods over the range of internal H contents for which IG fracture initiation was observed. It was also shown that grain-boundary alpha colonies or films are not responsible for the IG fracture initiation in the STA condition. A measured increase in hydrogen embrittlement (HG) susceptibility as a function of aging time at 500 C is consistent with the segregation or depletion of a critical species at the grain boundary. However, grain-boundary segregation/depletion could not be detected with Auger electron spectroscopy (AES) of specimens fracturing in a vacuum. Compression tests used to characterize and compare the alloys' slip behavior showed that plastic deformation is concentrated at or near the grain boundaries in the STA condition. Therefore, a possible intergranular fracture initiation mechanism that includes the effects of hydrogen and localized deformation is discussed.

• Research Organization: Naval Surface Warfare Center, West Bethesda, MD (US)
• OSTI ID: 20014047
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 31, Issue 1; Other Information: PBD: Jan 2000; ISSN 1073-5623
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRACK PROPAGATION
HYDROGEN EMBRITTLEMENT
TITANIUM BASE ALLOYS
ALUMINIUM ALLOYS
VANADIUM ALLOYS
CHROMIUM ALLOYS
MOLYBDENUM ALLOYS
ZIRCONIUM ALLOYS
GRAIN BOUNDARIES