Influence of hydrogen saturation on the structure and mechanical properties of Fe-17Cr-13Ni-3Mo-0.01С austenitic steel during rolling at different temperatures

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 2 2021 ties (Fig. 1, Table 1). At 25 % reduction, that is, at early deformation degrees, hydrogen saturation and a decrease in the test temperature insignificantly suppress the formation of {220}-type texture in the rolling plane. With an increase in the reduction up to 50 %, over against, both these factors contribute a significant increase in the relative intensity of austenitic 220γ line in comparison with a lower strain (Table 1). To - gether with data on the change in CSR values, this may indicate the activation of deformation twinning and/ or γ→ε deformation-induced transformation at low strains due to preliminary saturation with hydrogen and the decrease in the test temperature. Both these mechanisms contribute the formation of special boundaries Σ3 n , which inhibit dislocations motion, propagation of microshear bands, and impede the formation of a misoriented grain/subgrain structure with boundaries of general type [28–30]. As a result of the destruction of the grid of the special boundaries, which has been formed at small strains, the rolling texture is formed during subsequent rolling to 50 % reduction by analogy with specimens deformed without preliminary saturation with hydrogen (Fig. 1, Table 1). Results of transmission electron microscopic studies The initial specimens have the homogeneous grain structure. The average grain size of austenite is 15 μm, as it is determined by EBSD-maps. Chemical-deformation processing promotes significant grain refinement and the formation of a grain/subgrain structure with a high density of defects of the crystal structure (Figs. 2 and 3). The dislocation density increases from ~1012 to ~1015 m –2 during rolling. c d Fig. 2. TEM images of the microstructure in steel after processing in regime I: а , c – rolling of hydrogen-free specimens; b , d – rolling of hydrogen-charged specimens. Reduction:25%( a , b )and50%( c , d ).Selectedareaelectrondiffractionpatternsareobtainedfrom an area of 1.4 μm 2 a b