Issue 49

S. Smirnov et alii, Frattura ed Integrità Strutturale, 49 (2019) 201-211; DOI: 10.3221/IGF-ESIS.49.21 207 experimental data with the approximation reliability coefficient R 2 > 0.96 in the studied temperature ranges. Figure 5 shows the test temperature dependences of the creep rates of the materials, which have been obtained from calculating by Eq. (4), and the data obtained from experimental data processing. Environment ΔH, kJ/mol A 10 -4 n Temperature range, K VT1-0 air 273 18.7 6.77 900 – 1100 argon 302 13.5 2.83 1050 – 1350 VT5-1 air 260 8.06 4.17 950 – 1200 argon 307 9.48 3.09 1100 – 1350 Table 1 : The values of activation energy and the empirical coefficients in Eq. (4) The statistical processing of the experimental results on the determination of the conventional short-term creep strength 120 / .  has revealed that the values of the heating temperature 1/2.0 T at which the nominal stresses cause permanent creep strain of 0.2% within a 1-hour hold are related to the values of 120 / .  through the polynomial dependence (the approximation reliability coefficient R 2 > 0.98)      2 0.2/1 1 0,2/1 2 0.2/1 3 T c c c , (6) where c 1 , c 2 and c 3 are the approximation coefficients given in Table 2. Environment c 1 c 2 c 3 Temperature range, K VT1-0 air -1.25 -13.09 1054.6 800 – 1050 argon -0.96 -14.81 1194.5 950 – 1200 VT5-1 air -0.835 -16.59 1120.4 850 – 1100 argon -0.54 -20.74 1244.2 1000 – 1200 Table 2 : The values of the empirical coefficients in Eq. (6) The coefficients c 1 and c 2 are physically meaningless, and the coefficient c 3 can be treated as the temperature at which creep develops unaffected by external stresses. The experimental data on the determination conventional short-term creep strength 1/2.0  and the results of calculations by Eq. (6) are given in Fig. 6. Figure 6 : Conventional short-term creep strength as dependent on heating temperature (1.Ti–5Al - in the argon environment; 2. Grade 2. - in the argon environment; 3. Ti–5Al - in the air environment; 4. Grade 2 - in the air environment). 700 900 1100 1300 0 2 4 6 8 10 12 Temperature / K Creep strength / MPa 1 2 3 4