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Isothermal oxidation testing of near α titanium alloys VT18U, VT20, Ti6Al7Nb and Ti6242S was performed in air at 560 °С for 1000 hours. Parameters of diffusion layer on the alloy surfaces were studied by microhardness indentations, optical microscopy, X-ray diffraction analysis and nuclear microanalysis. It was established that concentration of oxygen in diffusion layer of tested alloys after oxidation differs significantly. An approach was demonstrated and validated by nuclear microanalysis data that allows comparative evaluation of the total concentration of interstitial impurities in the diffusion layer by the X-ray diffraction method.

The influence of the isothermal annealing conditions in air (at 560 and 625°C for 1000 h) on the deformation behavior of a high-temperature VT18U titanium alloy under tension is studied. The plasticity of the alloy at room temperature decreases from 14 to ≈5% after annealing at the investigated temperatures. The thickness of the gas-saturated layer is 17 and 42 μm after annealing at 560 and 625°C, respectively. The main factor determining the plasticity of the alloy in the oxidized state is the oxygen content gradient in the gassaturated layer.

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