Crystallography of upper bainite in Fe-Ni-C alloys

T. Furuhara, H. Kawata, S. Morito, T. Maki

Research output: Contribution to journalArticlepeer-review

160 Citations (Scopus)


The upper bainite structures were investigated in Fe-9Ni-(0.15-0.5)C (mass%) alloys transformed at temperatures between 723 and 623 K. A bainite packet similar to lath martensite is formed and is partitioned into blocks containing lath-shaped bainitic ferrite with the same parallel close-packed plane relationship of the K-S relationship. Its feature is categorized into three types: (A) a packet contains laths of two K-S variants with a small misorientation (sub-blocks), (B) a packet is divided by blocks largely misoriented and each block contains sub-blocks and (C) a packet is divided by blocks containing a single variant of laths. A packet of type (A) is formed at 723 K in each alloy whereas the packet type becomes (B) or (C) at lower temperatures. As a result, bainite blocks are refined with decreases in transformation temperature and carbon content. In contrast, blocks and packets of lath martensite are refined with increasing carbon content.

Original languageEnglish
Pages (from-to)228-236
Number of pages9
JournalMaterials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
Issue number1-2
Publication statusPublished - 2006 Sept 15


  • Bainite
  • Crystallography
  • Martensite
  • Phase transformation
  • Steel


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