Rheological Properties of the EP742-ID Alloy in the Context of Integrated Computational Materials Science and Engineering: Part I. Results of Experimental Investigations

Rheological properties of the EP742-ID alloy are investigated during high-temperature compression tests of cylindrical samples with various ratios of homological initial sizes of diameter and height (d₀/h₀). It is shown by the results of tests in ranges of temperature t = 1000–1150°C and initial deformation rates ε̇₀= 3 × 10^–2–3 × 10^–4 s^–1 that an increase in the compression flow tension manifests itself at all temperatures and deformation rates with an increase in ratio d₀/h₀ with the linear dependence on the magnitude of ε̇₀ and ratio d₀/h₀. The procedure of recalculating characteristics of the deformation resistance for the specified ratio of homological parameters is proposed. An increase in the compression flow tension is associated with an increase in the rigidity coefficient of the samples and their specific contact surfaces. The temperature dependence of the apparent activation energy of the plastic deformation (Q_def) of the alloy and its relation with the phase composition and running conditions of the dynamic recrystallization of the γ-solid solution are established. The magnitude of Q_def in temperature conditions of the development onset of the dynamic recrystallization of the γ-solid solution (1000–1050°C) is 959 kJ/mol for samples with d₀/h₀ = 0.75. The largest values of Q_def for the samples with d₀/h₀ = 0.75 equal to 1248 and 1790 kJ/mol are observed in a temperature region of the intense dissolution and coagulation of the grain-boundary γ′-phase (1050–1100°C). The value of Q_def for the samples with d₀/h₀ = 3.0 increases to 2277 kJ/mol in this temperature range. The apparent activation energy of the plastic deformation lowers to 869 kJ/mol in the temperature region of the γ-solid solution with grain-boundary primary and secondary carbides (1100–1150°C). The results of compression of alloy samples during single and repeated sequential loading with various durations of pauses between deformation actions are presented. It is shown that no metadynamic recrystallization occurs in the experimental conditions in the γ + γ′-region, while it runs slowly in the γ-region.