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A Brief Review of κ-Carbide in Fe-Mn-Al-C Model Alloys
Applied Microscopy 2018;48:117-21
Published online December 28, 2018
© 2018 Korean Society of Microscopy.

Jae Bok Seol

National Institute for Nanomaterials Technology (NINT), POSTECH, Pohang 37673, Korea
Correspondence to: Seol JB,, Tel: +82-54-279-0220, Fax: +82-54-279-0249, E-mail:
Received December 21, 2018; Revised December 26, 2018; Accepted December 27, 2018.
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

The multiple length scale analysis of previously designed Fe-Mn-Al-C based low-density model alloys reveals the difference in ordered κ-carbide, (Fe,Mn)3AlCx, between Fe-25Mn-16Al-5.2C (at%) alloy and Fe-3Mn-10Al-1.2C (at%) alloy. For the former alloy composition consisting of fully austenite grains, κ-carbide showed majorly cuboidal and minorly pancake morphology and its chemical composition was not changed through aging for 24 h and 168 h at 600°C. Meanwhile, for the isothermally annealed ferritic alloy system for 1 hr at 500 and 600°C, the dramatic change in the chemical composition of needle-shape κ-carbide, (Fe,Mn)3(Fe,Al)Cx, was found. Here we address that the compositional fluctuations in the vicinity of the carbides are significantly controlled by abutting phase, either austenite or ferrite. Namely, the cooperative ordering of carbon and Al is an important factor contributing to carbide formation in the high-Mn and high-Al alloyed austenitic steel, while the carbon and Mn for the low-Mn and high Al alloyed ferritic steel.

Keywords : Low-density steels, High manganese and aluminum alloyed steels, Ordered carbides, Transmission electron microscopy, Atom probe tomography
Fig. 1. TEM micrographs of κ-carbides, obtained from (A) high-Mn high-Al austenitic steels (; ) and from (B) low-Mn high-Al ferritic steels ().
Fig. 2. Atom maps of C, Mn and Al, and corresponding concentration profiles across matrix-carbide interfaces, taken from (A) high-Mn high-Al austenitic steels () and (B) low-Mn high-Al ferritic steels ().
Fig. 3. SEM image of slip formation during nano-indentation testing.
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December 2018, 48 (4)
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