Part 1: The effects of pre-dissolved hydrogen on cleavage and grain boundary fracture initiation in metastable beta Ti-3Al-8V-6Cr-4Mo-4Zr

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-999-0196-4· OSTI ID:316070

Gaudett, M A; Scully, J R ^[1]

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1. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

The effects of electrochemically pre-dissolved hydrogen on room-temperature fracture initiation in Beta-C titanium (Ti-3Al-8V-6Cr-4Mo-4Zr wt pct) have been investigated using circumferentially notched tensile specimens. Finite element-based analysis of notch stress fields was used to define relationships between the local threshold stress for crack initiation vs total internal hydrogen concentration. The as-received, solution heat treated (ST, {sigma}{sub y.2} pct = 865 MPa) and the ST + peak-aged conditions (STA, {sigma}{sub y.2%} pct = 1260 MPa) were compared after defining the relationships between the fracture process zone hydrogen concentration, hydrogen-metal interactions (i.e., hydrostatic stress field occlusion, trapping, hydriding), and the resulting fracture initiation behavior of each. Solutionized + peak-aged ({beta} + {alpha}) Beta-C fractured intergranularly above total hydrogen concentrations of {approximately}1000 wt ppm (5.1 at. pct). A fracture mode consistent with cleavage occurred at {approximately}2100 wt ppm (10.7 at. pct). Solutionized Beta-C resisted hydrogen-assisted cracking (e.g., did not crack intergranularly) but was not immune; cleavage cracking was provoked at {approximately}4000 wt ppm (20.4 at. pct). Cold-worked ST Beta-C (CW, {sigma}{sub y.2} pct = 1107 MPa) did not crack intergranularly; fracture initiation behavior was similar to the St condition regardless of specimen orientation. Fractographic evidence and finite element results show that a finite plastic zone exists prior to intergranular fracture of the STA condition. This suggests that a criterion for fracture that incorporates plastic strain and stress should be considered.

• Sponsoring Organization: USDOE
• OSTI ID: 316070
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 1 Vol. 30; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
FINITE ELEMENT METHOD
FRACTURE PROPERTIES
HYDROGEN
METALLURGICAL EFFECTS
MOLYBDENUM ALLOYS
TITANIUM BASE ALLOYS
VANADIUM ALLOYS
ZIRCONIUM ALLOYS