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An atomic transition model of a face-centered cubic(fcc) crystal to a primitive hexagonal x and body-centered cubic(bcc) structures has been crystallographically built. The fcc structure can transform into the x structure through a local shuffling or displacement of atoms about 0.4014 in iron for afcc iron= 3.59 . The bcc structure can form either after the x formation or concurrently by the similar mechanism, or the x structure can be treated as an intermediate stage during the transition of fcc→ω + bcc. Such a transition(fcc→ω + bcc transition) can be confirmed by Widmansta¨tten pattern formed in an iron meteorite, pearlitic structure and martensite composed of bcc-ferrite and ultra-fine x particles in iron–carbon steels. The present fcc–bcc orientation relationship matches with Pitsch’s one.
An atomic transition model of a face-centered cubic (fcc) crystal to a primitive hexagonal x and body-centered cubic (bcc) structures has been crystallographically built. The fcc structure can transform into x structure through a local shuffling or displacement of atoms about 0.4014 in iron for afcc iron = 3.59 . The bcc structure can form either after the x formation or concurrently by the similar mechanism, or the x structure can be treated as an intermediate stage during the transition of fcc → ω + bcc. Such a transition (fcc → ω + bcc transition) can be confirmed by Widmansta¨tten pattern formed in an iron meteorite, pearlitic structure and martensite composed of bcc-ferrite and ultra-fine x particles in iron-carbon steels. The present fcc- bcc orientation relationship matches with Pitsch’s one.