Issue 74

M. C. Marinelli et alii, Fracture and Structural Integrity, 74 (2025) 129-151; DOI: 10.3221/IGF-ESIS.74.09

such as dislocation tangles, wall-like dislocation structures, and interactions between dislocations and precipitates (highlighted in Fig. 3a). These characteristics are typical of ferritic-pearlitic steel sheets, where rolling induces dislocations that accumulate producing strain hardening [6,11]. Additionally, Fig. 3b shows randomly distributed cementite precipitates, while Fig. 3c provides a detailed view of pearlite as a lamellar structure composed of alternating ferrite and cementite layers. The average interlamellar spacing within the pearlite is 0.3 μ m.

(a) (c) Figure 3: TEM BF micrograph showing dislocation structure in the as-received condition: (a) dislocation tangles, wall-like dislocation and dislocation-precipitate interactions in ferrite; (b) non-uniform distribution of cementite; (c) uniform distribution of cementite. (b)

(a)

(b)

(c) Figure 4: Texture analysis of HSLA-420: (a) X-ray Diffractogram; (b) Normalized experimental and recalculated pole figures; (c) Φ 2 = 45° ODF section. The crystallographic texture of the HSLA-420 steel was analysed using XRD. The diffractogram presented in Fig. 4a indicates that, despite the steel containing approximately 20% pearlite, the diffraction peaks corresponding to cementite are scarcely visible. The nanometric spacing of cementite lamellae within the pearlite colonies induce an extreme peak broadening, resulting in low cementite peak intensities that are indistinguishable from background noise. Furthermore, the diffraction pattern is dominated by reflections from the ferrite phase, with the overall crystallographic texture governed by the body-centred cubic (BCC) ferrite matrix.

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