PSI - Issue 40

S.V. Danilov et al. / Procedia Structural Integrity 40 (2022) 112–117 S.V. Danilov at al. / Structural Integrity Procedia 00 (2022) 000 – 000

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Table 1. Mechanical properties of the 06Mn2MoNb steel specimens obtained by means of tensile testing. Mode YS, MPa UTS, MPa BS, MPa UE, % LE, % Elongation, % I 445 ± 11 560 ± 18 290 ± 4 12.5 ± 0.8 17.5 ± 1.0 30.0 ± 1.0 II 515 ± 9 610 ± 12 310 ± 5 9. 0 ± 0.7 14. 0 ± 0.7 23.0 ± 1.0 III 545 ± 9 620 ± 10 275 ± 4 9. 0 ± 0.7 15. 0 ± 0.8 24.0 ± 0.6

Fig. 3. Fracture surfaces of cylindrical specimens after standard tensile testing (a – c) and plate central area microstructure in the form of EBSD orientation maps with highlighted <100> orientation orthogonal to the figure plane (d – f) of 06Mn2MoNb steel after different TMCP: (a), (d) – after mode I; (b), (e) – after mode II; (c), (f) – after mode III. The anisotropy of structure and shape alteration of the specimens is evidently associated with the presence of a pronounced crystallographic texture (Fig. 2). Therefore, the more disperse texture of specimens after mode I (Fig. 2, а) suggests a higher deformation isotropy during fracture – the reduced section of the specimen obtains a less pronounced ellipsoid shape (Fig. 3, а – с). Oxford Instruments software allows to construct microstructure orientation maps with any axial orientations highlighted by means of a specific processing of the diffraction pictures. It is also possible to plot the distribution of the angle deviations between the axes and some preset directions with respect to the hot rolling coordinate system. This was used to construct orientation maps with highlighted orientations, whose planes {001} were parallel to one of three planes forming a coordinate cube (Fig. 3, d – f). Geometrical location of the separations remains the same in all the specimens for all processing parameters. Positioning of the separations in the microstructure deffinetly corresponds to the presence of areas with {001}<110> orientation with one of the planes {001} parallel to the rolling plane and one of the directions <110> parallel to rolling direction (Fig. 3, d – f), which have been formed due to the formation of outstretched ferrite grains during rolling.