Electron diffraction analysis of quenched Fe–C martensite

Abstract

Martensite has a body-centered tetragonal (bct) structure in high carbon steels. However, body-centered cubic (bcc) {112} 〈111〉-type twins instead of bct twins always be observed as the substructure of martensite in high carbon steels. In this paper, martensitic substructure in a quenched high carbon Fe-1.4C (wt%) alloy has been investigated in detail using selected area electron diffraction (SAED) technique in a conventional transmission electron microscopy. The reciprocal lattice of martensite has been built based on the experimental SAED patterns. Two sets of diffraction spots (one face-centered cubic lattice and one hexagonal lattice) in the built reciprocal lattice suggest that two crystalline phases with bcc (or α-Fe) and hexagonal (ω-Fe) structure actually coexist in the twinned martensite. The two-phase diffraction spot patterns from the reciprocal lattice can match perfectly with the experimental results. The fact that the {0001}ω diffraction spot at the 1/3{222}α position and the {0002}ω at 2/3{222}α can support the ω-Fe existence in the twinned martensite.

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Acknowledgements

This work was supported by JSPS KAKENHI Grant Number JP15H02304.

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Correspondence to T. W. Liu or D. H. Ping.

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Liu, T.W., Ping, D.H., Ohmura, T. et al. Electron diffraction analysis of quenched Fe–C martensite. J Mater Sci 53, 2976–2984 (2018). https://doi.org/10.1007/s10853-017-1731-0

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Keywords

  • SAED Pattern
  • Extra Diffraction Spots
  • Reciprocal Lattice
  • High-carbon Martensite
  • Twin Boundary Region