APPLICATION OF ELLIPSOMETRY TO OXIDATION STUDIES OF BINARY TITANIUM-ALUMINUM ALLOYS

An in situ test cell and auxiliary apparatus was constructed for the purpose of making ellipsometer measurements on bulk metals and alloys in vacuum and in pure and premixed gases. Contamination on freshly polished surfaces of titanium and titanium-aluminum alloys is substantially reduced by heating, in vacuum, to 177°C. The computed refractive index and absorption coefficient for pure titanium after this treatment agrees reasonably well with published data. The refractive indices of similarly heated titanium-aluminum alloys are greater than that of pure titanium. The optical constants are quite dependent on the thickness of the oxide layer in the range between 40-250 Å. The reproducibility of change in thickness versus time profiles is very good and indicates that a meaningful comparison of oxidation rates for various alloys can be made. © 1969.