Sustained-Load Cracking of Titanium: A Survey of 6Al-4V Alloys.
NAVAL RESEARCH LAB WASHINGTON D C
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This survey reveals that degradation in load-carrying capacity owing to sustained-load cracking SLC is widespread and serious in alloys of the Ti-6Al-4V family. Each of eight different one inch 2.5-cm thick plates tested in air at room temperature exhibited the effect, with degradations ranging up to 35. The amount of degradation does not seem to correlate with differences in hydrogen content, processing variables, or strength and toughness levels however, the susceptibility to SLC is orientation dependent. Invalidity of several of the rising-load fracture toughness values, with respect to plane-strain criteria, makes quantitative comparison of degradations uncertain. However, the threshold stress-intensity factor below which SLC failures will not occur, KIt, clearly represents a more conservative fracture-safe design parameter than the plane-strain fracture toughness KIc, which cannot account for insidious time-delayed failures owing to SLC. Author
- Metallurgy and Metallography