Structure restoration and coarsening of nanocrystalline cementite in cold drawn pearlitic wire induced by low temperature annealing

Lichu Zhou, Feng Fang*, Masayoshi Kumagai, Ed Pickering, Tianbo Yu, Xiaodan Zhang*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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 languageEnglish
Article number114696
JournalScripta Materialia
Volume215
ISSN1359-6462
DOIs
Publication statusPublished - 2022

Keywords

  • Nanocrystalline cementite
  • Structure restoration and growth
  • Pearlitic steel
  • Low-temperature annealing

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