PSI - Issue 26

Jesús Toribio et al. / Procedia Structural Integrity 26 (2020) 368–375 Toribio / Structural Integrity Procedia 00 (2019) 000 – 000

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7. Between Donatello and Michelangelo Previous section (fractographic analysis) showed that HAMD in pearlitic microstructure ( either oriented or not ) are produced at the finest micro-level by plastic tearing in the form, in general, of HDT with different appearances depending of the cold drawing degree , evolving from the so-called TTS in hot-rolled steel (not cold-drawn at all) to a sort of EOTTS in heavily drawn steels (the pronounced enlargement and marked orientation being along the wire axis or cold drawing direction). The following sub-sections discuss the cases of microstructural isotropy (non oriented or randomly-oriented pearlitic microstructures related to steels with zero or low degree of cold drawing, e.g., a hot rolled steel, not cold drawn at all) and microstructural anisotropy (oriented pearlitic microstructures related to steels with elevated degree of cold drawing and associated high level of cumulative plastic strain, i.e., heavily cold drawn pearlitic steels). 7.1. Randomly oriented pearlite with microstructural isotropy in hot rolled or slightly cold drawn pearlitic steels: Resembling Michelangelo Stone Sculpture Texture (MSST) In non-oriented (or randomly oriented) pearlitic microstructures the HAMD takes place in the form of TTS, as shown in Fig. 6, cf. Fig. 4b. It resembles the Michelangelo Stone Sculpture Texture (MSST), see Fig. 7.

Fig. 6. Hydrogen-assisted micro-damage (HAMD) in non-oriented pearlite: tearing topography surface (TTS), cf. Fig. 4b.

Fig. 7. Works by Michelangelo: Pietà di Firenze and Pietà Rondanini .