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We have investigated the influence of the deformation temperature from 25°C (RT) to -196°C on the dislocation structures associated with strain localization phenomena in an austenitic Fe-30Mn-6.5Al-0.3C (wt.%) low-density steel by combined electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD) techniques. The main characteristics of the dislocation structures were evaluated on the main texture components, i.e. <111>//tensile axis, <112>//tensile axis, and <001>//tensile axis directions. Cryogenic deformation temperatures promote the inhomogeneous character of the plastic behavior due to the enhanced formation of dislocation structures associated with strain localization, namely microbands (MBs) and deformation bands (DBs). The deformation temperature has a strong influence on the thermal-assisted dislocation processes controlling the dislocation configurations and MB formation mechanisms. MB nucleation mechanism evolves from a cross-slip assisted mechanism (RT) to a slip band-assisted mechanism (cryogenic temperatures). This effect has a profound effect on the grain orientation dependence of the MB structure but does not influence its crystallographic alignment. From a mechanical standpoint, cryogenic deformation temperatures enhance strain-hardening due to the activation at moderated strain levels (0.3) of a hardening stage associated with secondary twinning. This effect is associated with the reduction of the γ_SFE at cryogenic temperatures. ECCI analysis reveals MBs and DBs have a small contribution to strain-hardening and ductility. These effects are associated with the small mechanical resistance of these dislocation structures against the advance of twin boundaries and dense dislocation layers, and the comparatively small plastic strain accommodated by these structures, respectively.

権利情報:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

キーワード: FeMnAlC low-density steels, Strain localization, Austenitic steels, Strain-hardening, Electron channeling contrast imaging (ECCI)

刊行年月日: 2023-12-02

出版者: Elsevier BV

掲載誌:

• Acta Materialia (ISSN: 13596454) vol. 264 119566

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1016/j.actamat.2023.119566

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更新時刻: 2024-11-21 16:30:25 +0900

MDRでの公開時刻: 2024-11-21 16:30:25 +0900