Open AccessA study of nitride formation during the oxidation of titanium-tantalum alloys
Author(s) -
Robert J. Hanrahan,
Yeqing Lu,
H. Kung,
Darryl P. Butt
Publication year - 1996
Language(s) - English
Resource type - Reports
DOI - 10.2172/418500
Subject(s) - nitride , materials science , titanium nitride , tantalum , tin , dissolution , oxygen , transmission electron microscopy , diffusion , layer (electronics) , tantalum nitride , metallurgy , substrate (aquarium) , diffusion barrier , phase (matter) , titanium , metal , barrier layer , chemical engineering , chemistry , nanotechnology , physics , oceanography , organic chemistry , geology , engineering , thermodynamics
The oxidation rates of Ti rich titanium-tantalum alloys are significantly lower in air than in oxygen. This nitrogen effect has been shown to be associated with the formation of a nitride layer at or near the scale-metal interface. In the present work the authors used transmission electron microscopy and microdiffraction to identify the nitrides formed on Ti5Ta and Ti40Ta (5 and 40 weight percent Ta alloys) during identical exposures. In both alloys the nitride develops in contact with the oxygen stabilized {alpha}-phase in the substrate. In Ti5Ta a continuous layer of TiN forms, while in Ti40Ta a discontinuous layer of Ti{sub 2}N interspersed with Ta{sub 2}O{sub 5} (formed from the Ta rich {beta}-phase) is formed. The nitride layer acts as an oxygen diffusion barrier, reducing the dissolution of oxygen in the substrate