Crystal Structure of Carbon Steel Martensite
V. A. Lobodyuk, Yu. Ya. Meshkov
G. V. Kurdyumov Institute for Metal Physics, NAS of Ukraine, 36 Academician Vernadsky Blvd., UA-03142 Kyiv, Ukraine
Received: 29.05.2019; final version - 21.10.2019. Download: PDF
Results of the researches of the crystalline structure of carbon steels martensite are analysed. Embedding of carbon atoms in steel (up to 1,7% mass. or $\cong$ 8 at.%) on one of the $a$, $b$, $c$ edges of the b.c.c. lattice of the martensitic phase (b.c.c. $\alpha$-Fe type) results in the increase of this edge and corresponding changes of the closely spaced edges. In this case, the crystalline structure of the martensite can be presented as a set of blocks of four distorted b.c.c. lattices with different sizes of the $a$, $b$, $c$ lattice edges. Under the ordered location of carbon atoms only on $c$ lattice edge, a pseudotetragonal structure arises, that results in an appearance of doublets of the diffraction lines. In the case of unordered (chaotic) location of the C atoms (on any of the lattice edge $a$, $b$, $c$) martensitic structure remains cubic one and the diffraction lines are broadening. The crystalline structure of martensite is well enough described also by root-mean-square displacements of the Fe atoms from positions of equilibrium caused by periodic insertion of the carbon atoms on $c$ crystal edges of b.c.c. lattice of the martensitic phase.
Key words: carbon steel, martensite, crystal structure, ordering, blocks of sublattices, tetragonality, pseudotetragonality.
PACS: 61.50.Ks, 61.66.Dk, 61.72.Bb, 61.72.Dd, 61.72.S-, 81.30.Kf
Citation: V. A. Lobodyuk and Yu. Ya. Meshkov, Crystal Structure of Carbon Steel Martensite, Metallofiz. Noveishie Tekhnol., 42, No. 1: 123—142 (2020) (in Russian)