Formation of Fe₇C₃ and Fe₅C₂ type metastable carbides during the crystallization of an amorphous Fe₇₅C₂₅ alloy

The crystallization of a sputter-deposited Fe75C25 film has been studied by transmission electron microscopy. The crystallization process can be described by the successive reactions. Amorphous → Amorphous + MS I → MS I + MS II → Fe3C, where the metastable phases MS I and MS II have been identified as Fe7C3 and Fe5C2 type carbides. The first reaction gives rise to a resistivity decrease at about 460 K, while the second reaction takes place at about 590 K. Diffusion lines, associated with a [00.1] linear disorder, are observed on the electron diffraction patterns of "Fe7C3". The crystallization mechanisms of amorphous FeC alloys are similar to those of (Fe, Co, Ni)SiB with three carbon concentration ranges. They are discussed in connection with the Gaskell model of amorphous transition metal-metalloid alloys. © 1981.