Non-crystallographic symmetry of liquid metal, flat crystallographic faults and polymorph transformation of the M sub(7)C sub(3) carbide

The fine lamellar fault structure of primary M sub(7)C sub(3) 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 M sub(7)C sub(3), M sub(5)C sub(2), M sub(3)C and M sub(23)C sub(6) carbides and constructions of the projective 10 sub(3) Desargues configuration and its subconfigurations is shown. Mutual mapping between 10 sub(3) Desargues subconfigurations determines transformations of the ten-vertex equal-edged triangulated clusters appearing as building units of these carbides. The crystal structures of M sub(7)C sub(3), M sub(5)C sub(2), M sub(3)C and M sub(23)C sub(6) carbides are determined by the finite projective geometry constructions, namely the Desargues configuration 10 sub(3) 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.