Surface Oxidation and Fast 18O Implant Diffusion in Nanostructured Layers of Ti-6Al-4V Alloy

Authors S.M. Duvanov1 , A.G. Balogh2

1 Institute of Applied Physics, National Academy of Sciences of Ukraine, 58, Petropavlivska Str., 40030 Sumy, Ukraine

2 Institute of Material Science, Darmstadt University for Technology, 23, Petersen Str., 64287 Darmstadt, Germany

Issue Volume 7, Year 2015, Number 2
Dates Received 14 April 2015; published online 10 June 2015
Citation S.M. Duvanov, A.G. Balogh, J. Nano- Electron. Phys. 7 No 2, 02028 (2015)
PACS Number(s) 68.55, 68.55. – a, 66.30.Pa
Keywords Ti-6Al-4V alloy, Ion implantation (5) , Thermal annealing (4) , Oxidation (4) , Diffusion (11) , Nanoparticle (77) .
Annotation A formation of the near surface barrier composite oxide film and two-stage 18O implant diffusion in modified layers of Ti-6Al-4V alloy were observed in the present work. Fast and super fast regimes occur during second stage of the diffusion. Sample modification was performed using ion implantation and subsequent thermal annealing in ultra-high vacuum (UHV) atmosphere. Parameters of ion implantation are the following: 18O+ ion energy of 30 keV; fluence of 3 × 1017 ion/cm2; RT. Post-implantation annealing was performed in the temperature range of 100…800 °С by a step of 100 °С. SIMS and SEM techniques were applied for the sample characterisation. Effective diffusion coefficients (EDC) of 18O implant were extracted from SIMS depth profiles. An Arrhenius plot of the EDC shows that 18O implant diffusion in Ti-6Al-4V proceeds by the two stage mechanism: i) athermal, radiation-enhanced diffusion in range of 100-400 °С; and ii) fast, thermally activated diffusion at 500-700 °С. A super fast regime of the diffusion occurs above 800 °С. A protective composite oxide film was formed in near surface alloy layers after annealing in the temperature range of 400-600 °С. Dissolution of this film was observed at 700-800 °С. Activation enthalpy values of 18O implant diffusion were obtained too. Migration of 18O implant correlates with a formation of the following dielectric inclusions of a new phase that are stable up to annealing at 800 °С: particles of average size of 30 nm; and column nanocrystals oriented perpendicularly to the sample surface. Details and possible mechanisms of 18O implant migration, surface oxide film formation, dielectric nanoinclusion formation and its thermal stability were discussed.

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