Metallurgical and Materials Transactions A

, Volume 38, Issue 9, pp 1991–2000 | Cite as

X-ray Diffraction Study on Cooling-Rate-Induced γ fccε hcp Martensitic Transformation in Cast-Homogenized Fe-26Mn-0.14C Austenitic Steel

  • P. SahuEmail author
  • A.S. Hamada
  • R.N. Ghosh
  • L.P. Karjalainen


The thermal stability of a cast homogenized austenitic steel with basic composition Fe-26Mn-0.14C has been studied using the Rietveld entire X-ray diffraction (XRD) pattern fitting technique. The decomposition of austenite was observed to be very sensitive to the cooling rate. A very high proportion (49 to 70 pct) of ε-martensites was found in the differently cooled specimens as well in the as-cast specimen. The density of various planar (stacking and twin) faults was also estimated in both ε-martensites and retained austenite. The significant variation in the extent of γ fccε hcp martensitic transformation was interpreted in terms of athermal and isothermal martensites formed during cooling and grain size of austenite. The austenite grains were found to be comprised of a high to moderate density of stacking faults (∼10−3 to 10−2) and negligible twin fault probability (∼10−5). On the other hand, in the ε-martensites, the dominant planar fault was twins (∼10−3). Approximate values of the dislocation density within the retained austenite were also evaluated using the crystallite size and root-mean-square (rms) strain values obtained from the “size-strain-shape” analyses.


Austenite Martensite Crystallite Size Dislocation Density Stack Fault Energy 
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Two of the authors (PS and RNG) are grateful to Professor S.P. Mehrotra, Director, National Metallurgical Laboratory, Jamshedpur, for his kind permission to publish the results.


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Authors and Affiliations

  • P. Sahu
    • 1
    Email author
  • A.S. Hamada
    • 2
  • R.N. Ghosh
    • 1
  • L.P. Karjalainen
    • 2
  1. 1.Materials Science and Technology DivisionNational Metallurgical LaboratoryJamshedpurIndia
  2. 2.Materials Engineering Laboratory, Department of Mechanical EngineeringUniversity of OuluOuluFinland

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