Abstract
Internal structure of nano-scale cementite has exhibited a critical
impact on mechanical performance for various heavily strained
high-carbon steel materials. Through a combination of post-annealing and
in-situ annealing transmission electron microscopy
observations, we investigated the structural evolution of heavily
strained cementite during low-temperature annealing. During annealing,
the morphology of the cementite lamellae is stable when the temperature (Ta) is lower than 350 °C. Meanwhile, lattice structure restoration and coarsening of nanocrystalline cementite (θ-NC) occur. Cementite lamellae, with a nanocrystalline structure in the as-drawn state were observed to transform into a coarsened isometric shape θ-NC (140 °C < Ta < 210 °C) or elongated θ-NC (210 °C < Ta < 350 °C). The coarsening activation energy of heavily strained cementite nanocrystals in the lamellae is estimated to be in a range of 37–50 kJ mol−1. The coarsening behavior is limited by the ferrite-cementite phase boundary.
Original language | English |
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Article number | 114696 |
Journal | Scripta Materialia |
Volume | 215 |
ISSN | 1359-6462 |
DOIs | |
Publication status | Published - 2022 |
Keywords
- Nanocrystalline cementite
- Structure restoration and growth
- Pearlitic steel
- Low-temperature annealing