All-Russian Scientific Research Institute of Aviation Materials, Moscow, Russia:

M. S. Belyaev, Leading Researcher, e-mail: bms-oti@mail.ru
M. A. Gorbovets, Head of a Sector
O. S. Kashapov, Leading Engineer
I. A. Khodinev, First Category Engineer

There was researched the dependence of main strength characteristics (including the fatigue crack growth rate) from the structural state of heat-resistant titanium alloy VT41 (ВТ41) at the temperatures of 20 ^oC and 600 ^oC. Research was carried out on the samples, made of forgings, manufactured by two different schemes: with final deformation at onephase and two-phase area temperatures. According to this, there were obtained the coarse plate-like and fine globular plate-like structures. The globular plate-like structure has more complex structural-phase state, which is substantiated by application of stepwise mode of thermal processing. The paper provides a detailed description of obtained structures, phase composition and basic mechanical properties. The fatigue crack growth rate tests were carried out under eccentric tension of compact sample with dimensions of 60×62×10 mm. The test procedure corresponds to Russian technical standards, and to the ASTM E647–08 standard. Having both test temperatures, the plastic-like structure alloy VT41 has a slower rate of fatigue cracks development, than the fine globular plate-like structure alloy VT41. At the same time, increase of test temperature from 20 ^oC to 600 ^oC causes a reduction in fatigue crack growth rate. The defined difference of fatigue crack growth rate of material with various structure parameters is primarily substantiated by the beta-grain size. The rate of fatigue crack of globular plate-like structure alloy grows with disperse releases of silicides on interphase boundaries, formed by double annealing, and with the presence of Ti3Al phase. Comparison of lamellar structure alloy VT41 and heat-resistant titanium alloy in the same IMI-834 class showed that at the test temperature of 600 ^oC, characteristics of fatigue crack growth rate are similar. At the test temperature of 20 ^oC, VT41 alloy has higher fatigue crack growth rate values.

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