PSI - Issue 23

W. Teraud et al. / Procedia Structural Integrity 23 (2019) 390–395 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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3.2. Microstructure For experiments Nos. 10, 12 and 13, additional studies of samples were carried out at the Moscow Aviation Institute, the results are presented in the table 2. Vickers HV microhardness measurement was carried out on a MicroMet 5101 microhardness meter with a load of 50 g at five points, and the results were processed using the program ImageExpert MicroHardness 2. The results of this measurement strongly depended on the indenter hit point, so the load 150 kgf (HRC) was also measured on the MacroMed 5100T hardness tester. Obviously, the hardness decreases with increasing hydrogen concentration, however, the limiting deformation p * does not increase. The dimensions of the crystallographic lattice of the  -phase c  and a  decrease with increasing C H concentration.

Table 2. The parameters of the examined specimens. (**) – does not measure by x-ray method. № C H , % HV (50g) HRC c  , nm a  , nm a  , nm n  , % 10 0.28 377 36.2 0.4622 0.2916 0.334 25 12 0.0 416 40.2 0.4654 0.2974 - ** 13 0.1 480 37.2 0.4640 0.2950 - **

The survey of metallographic thin sections was carried out with an Axio Observer.A1m microscope. The structure was removed from two places at  280,  450,  600 and  1100 magnifications. Examples of images obtained are shown in Fig. 2 at  1100 magnification. In the figure, the white zones correspond to the  -phase. The numerical values of the n  relative content of the  -phase in the sample, obtained by averaging over two points, are given in table 2. From the photographs of metallographic thin sections, the area of bright areas corresponding to the  -phase was calculated. Measurements show that as the level of hydrogen rises, the amount of the stronger  -phase decreases.

a)

b)

c)

Fig. 2. An microstructure of the experiments (a) - №10 C H =0.28%, (b) - №12 C H =0.1% and (c) - №13 C H =0.0% with scale  1100.

4. Conclusion

It is shown that the development of localization in a sample can occupy a significant part of the life cycle of a sample. Hydrogen embedded in the structure of titanium alloy VT-6 significantly reduces the time of uniform deformation and leads to extremely early formation of localization of creep deformations, which must be taken into account in technological processes of processing titanium alloy, in which hydrogen is additionally introduced to reduce shaping efforts. For the source material, the localization time is 83 %, with a hydrogen content of 0.1 %, it is 48 %, and with a content of 0.28 % it decreases to 36 % of the time before destruction.

Acknowledgements

The work was partly supported by a grant from the President of the Russian Federation (MK-4321.2018.1). The authors are grateful to Lokoshchenko A.M. for the attention to work.