Phase Equilibria in the Carbide Region of Iron–Carbon Phase Diagram

Autor: S. V. Davydov
Rok vydání: 2020
Předmět:
Zdroj: Steel in Translation. 50:888-896
ISSN: 1935-0988
0967-0912
DOI: 10.3103/s0967091220120025
Popis: The main evolution stages of the phase diagram of Fe–C in the carbide region (on the right from the cementite line) is a recently discussed theoretical topic that has been considered. It has been determined that previously isolated e-Fe2C, χ-Fe5C2, and g-Fe7C3 carbides (except for cementite Θ-Fe3C) are nonstoichiometric compounds. Thus, they are variable composition phases containing stoichiometric composition or second-type interstitial solid solutions based on daltonides and berthollides. It has been stated that the iron–cementite phase diagram can be identified as the iron–e-Fe2C carbide phase diagram in the concentration range of 0–9.7% C. The following phase transformations are introduced to the diagram: reaction of nonvariant syntectic equilibrium of cementite Θ-Fe3C crystallization; reaction of peritectic equilibrium of carbide χ-Fe5C2 crystallization; low-temperature peritectoid transformation of carbide, at which solid solutions of ferrite and cementite form solid solution possessing broad homogeneity range based on e-carbide Fe2C berthollide. It has been shown that the carbide phases represent a uniform isomorphous quasi-carbide solid solution, while the carbide phase crystallizes in the form of the carbide phase mixture as quasi-eutectics.
Databáze: OpenAIRE
Externí odkaz: