Non‐crystallographic symmetry of liquid metal, flat crystallographic faults and polymorph transformation of the M7C3 carbide

The fine lamellar fault structure of primary M7C3 carbide particles in the heat‐resistant Fe–Cr–Ni–C alloy of the HP series (0.45C–25Cr–35Ni) in the cast condition has been revealed using transmission electron microscopy. The lamellar fault structure is regarded as an inheritance of the initial melt structure. A one‐to‐one correspondence between the crystal structures of M7C3, M5C2, M3C and M23C6 carbides and constructions of the projective 103 Desargues configuration and its subconfigurations is shown. Mutual mapping between 103 Desargues subconfigurations determines transformations of the ten‐vertex equal‐edged triangulated clusters appearing as building units of these carbides. The crystal structures of M7C3, M5C2, M3C and M23C6 carbides are determined by the finite projective geometry constructions, namely the Desargues configuration 103 and its subconfigurations. The unique mechanism of the liquid‐crystal transition and in situ polymorph transformations between these carbides is described within the framework of the same approach.