Stress Corrosion Cracking of Titanium Alloys Preliminary Report on Ti:8al-1mo-1v Alloy and Proposed Electrochemical Mechanism

摘要

Stress corrosion cracking of titanium: 8% A1 - 1% Mo - 1% V alloy specimens was investigated in various salt solutions at controlled potentials applied by a potentiostat. Polarization curves on titanium oxide surfaces and kinetic data for oxidation of newly formed titanium alloy surface were also obtained. It was found that stress corrosion cracking of duplex annealed Ti:8-1-1 alloy occurred in chloride, bromide, and iodide solutions but did not occur in other solutions such as fluoride, hydroxide, sulfide, sulfate, nitrate or perchlorate. The ultimate strength was strongly dependent upon potential. The velocity of crack propagation and current flowing into the crack in chloride, bromide and iodide solutions were linearly related to the applied potential above a potential of -900 mv to the saturated colomel electrode. An electrochemical model was developed to interpret the data. Anodic reaction with the halides is considered to initiate at the -900 mv potential and the rate of crack propagation to be limited by the potential drop through the electrolyte in the crack. It is planned to extend the investigation to other alloys using the model as a guide for the design of experiments. (Author)