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THE STRESS-CORROSION AND ACCELERATED CRACK-PROPAGATION BEHAVIOR OF TITANIUM AND TITANIUM ALLOY
BATTELLE MEMORIAL INST COLUMBUS OH DEFENSE METALS INFORMATION CENTER
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This technical note summarizes information which has become available to DMIC on the stress-corrosion cracking and crack propagation behavior of titanium alloys in a variety of environments. Much of this information, particularly that regarding accelerated crack propagation in aqueous and liquid solutions, is preliminary and the conclusions offered herein should be viewed as tentative and subject to change as additional information becomes available. Almost all titanium alloys are susceptible to stress-corrosion cracking at elevated temperatures in chloride salts. This reaction shows a time-temperature- stress dependency in which the critical values of these three parameters vary significantly among the different titanium alloys. The mechanism of hot-salt stress-corrosion cracking apparently involves sodium chloride, oxygen, water, and reaction products of titanium dichloride, sodium hydroxide and titanium dioxide. Cyclic exposure from room temperature to test temperature greatly reduces the susceptibility to hot-salt stress-corrosion cracking. Silver and silver compounds may cause stress-corrosion cracking of titanium alloys at 700 F and above. A type of stress-corrosion cracking has also been observed in liquid nitrogen tetroxide at 105 F. Solutions of methyl alcohol containing hydrochloric or sulfuric acids also crack titanium as does contact with liquid mercury and molten cadmium. Titanium and its alloys also suffer severe stress-corrosion cracking andor pyrophoric reaction in dry, red fuming nitric acid.
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