HIGH-DOSE HE IMPLANTATION IN 2 TI ALLOYS - EFFECTS ON STRUCTURE AND THERMAL-OXIDATION

Implantation of inert gases such as helium into metals at sufficiently high doses can lead to a variety of buried bubble structures. In this work, motivated by the possibility of ultimately finding new or impro ved catalytic surfaces, we investigate the thermal oxidation of Ti6Al4 V and of Ti15V13Cr3Al after implantation of helium at doses up to 2.5 x 10(18) ions cm(-2). The coexistence of various phases in the alloys allows comparison of the different bubble structures formed in the dif ferent phases under otherwise identical conditions of temperature and dose. Using a combination of Nuclear Reaction Analysis (NRA), Rutherfo rd Backscattering Spectrometry (RBS), Raman Spectroscopy and Transmiss ion Electron Microscopy (TEM), we show that the buried helium structur es survive thermal oxidation at 550 degrees C; that the crystalline ox ide on both alloys consists only of mixed rutile and anatase phases; a nd that the oxide formed on the implanted alloys has a higher proporti on of anatase. (C) 1998 Elsevier Science B.V.