A Procedure for Investigating the Effect of Hydrogen Content on Toughness and Sustained Load Cracking Resistance of Titanium Alloys, with Some Results for Ti-6Al-4V

摘要

A procedure for measuring the effect of hydrogen content on the toughness and resistance to sustained load crack (SLC) growth of titanium alloys is presented. The results of such measurements on a high oxygen content, very high yield strength heat of 1-in. thick Ti-6Al-4V alloy (R-23B) are compared with results for a low oxygen content, moderately high yield strength heat (R-14). Both fracture toughness and SLC resistance of R-23B are greatly reduced by small amounts (35 ppm) of hydrogen added to vacuum annealed specimens. The fracture toughness, but not SLC resistance, of R-14 was likewise affected, in the hydrogen content range from 9 ppm to 125 ppm. The substantial gain in toughness due to vacuum annealing a commercial heat of Ti-6Al-4V (R-23B), without reduction in hardness, raises the possibility of developing a vacuum annealing schedule for greatly increasing the reliability of critical high strength structural parts. (Author)