Etude de la diffusion de l'oxygene dans le titane α oxyde entre 700 °c et 950 °c

Abstract

The diffusion of oxygen in the hexagonal compact structure of αtitanium was studied directly by nuclear microanalysis using polycrystalline samples, oxidized in pure oxygen under atmospheric pressure, at temperatures ranging from 700 °C to 950 °C. The diffusion profiles were determined point by point, which permitted calculation of the diffusion coefficient values, with an activation energy of 48 kcal mol −1. The concentration of oxygen at the metal-oxide interface is always less than 34 at.%, which is the saturation value suggested by the titanium-oxygen equilibrium diagram. The total amount of oxygen diffusing in the metal is calculated by integrating the concentration profiles and follows a parabolic law as a function of time. These profiles are not well fitted by erfc functions, however, which could indicate anomalies in the diffusion process with relation to the finely layered structure of the oxide. This study was completed by measuring the parameters a and c of the titanium unit cell as well as by measuring microhardness as a function of the oxygen content in solid solution. A metallographic examination was also performed.