SST Technology Follow-On Program, Phase I. Titanium Alloy 6Al-4V Hydrogen Effects
Final rept. 1966-1971 on Task 1
BOEING COMMERCIAL AIRPLANE CO SEATTLE WA
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This report summarizes the investigations on the effects of hydrogen in Ti-6Al-4V. The tests conducted include the effect of hydrogen content on fracture toughness, stress-corrosion resistance, and delayed-failure cracking. Hydrogen contents of up to 750 ppm had little effect on the fracture toughness and stress corrosion of beta-annealed and beta-STA 1250 F Ti-6Al-4V. Delayed failures were observed in room temperature air in beta annealed, beta-STA 1250 F, and STA 1000 F with hydrogen contents from 150-275 ppm. Failure times were shorter with the STA 1000 F heat treatment and with increasing H2 content. Hydrogen pickup during chemical milling was studied and found to be generally low, although isolated high amounts 100-150 ppm were observed. One instance of high hydrogen pickup was observed during a simple hot forming test. Hydrogen pickup appears to be a function of microstructure. A practical manufacturing outgassing procedure was developed to reduce the hydrogen content to less than 150 ppm. The procedure involved a vacuum treatment at 1150 F for 1 hr in a vacuum of 50 torr.
- Transport Aircraft
- Properties of Metals and Alloys
- Fabrication Metallurgy