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