Аннотация:It is known that titanium interacts very actively with hydrogen, and the phenomenon of hydrogen embrittlement occurs. In well-known works, hydrogen embrittlement and its effect on plasticity and long-term strength are investigated, on the one hand, and on the other, the localization of deformations in a material without regard to the hydrogen content is investigated, therefore, the effect of hydrogen on the localization of deformations was studied.
In tests, specimens of a two-phase titanium alloy (α+β) Ti–6Al–4V (grade VT6) were used. The test temperature was 450°C. A total of 15 experiments were conducted with a test duration from several hours to three weeks in the Institute of Mechanics of Lomonosov Moscow State University. Specimens of two types were used: initial and specimens with a high content of hydrogen. Six specimens of VT6 titanium alloy were prepared, which prior to experiments were pre-hydrogenated in the Moscow Aviation Institute laboratory by thermal diffusion method in Sievers equipment up to CH content of 0,1 %, 0,28 % and 0,6 % by weight of the specimen.
To determine the point in time in the experiment at which a neck is formed in the specimen, the developed force criterion for the occurrence of strain localization based on the virtual sample with the parameter k4 = 1,0 MPa is used.
As a result of the experiments, a database was obtained on the high-temperature deformation of a titanium alloy with the additional effect of implanted hydrogen in the metal structure and without this effect.
The plasticity of the specimens under the action of hydrogen, estimated from the uniform creep rate , increases 5 times for a concentration of CH = 0,1 % and more than 10 times for a concentration of hydrogen of CH = 0,28 %. The effect of hydrogen is most pronounced on the time to failure – t*.
With an initial stress of 0 = 345 MPa for hydrogen concentration CH = 0 % и CH = 0,1 %, the time t* decreases 2.8 times, and in comparison with CH = 0,28 % the time t* decreases almost 8 times. For the initial material, the localization time averages 83 % of the time to failure, with a hydrogen content of 0,1 %, it is 48 %, and with a content of 0,28 %, it decreases to 36 % of the time to destruction. For the initial stress 0 = 552 MPa we can see similar results.
For several experiments, a metallographic study was conducted. Measurements show that as the level of hydrogen rises, the amount of the stronger α-phase decreases. Measurement of microhardness showed that a decrease in values with increasing hydrogen concentration, however, in this case, the limiting deformation p* does not increase. The dimensions of the crystallographic lattice of the α-phase c and a decrease with increasing CH concentration.
