Abstract

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 ε-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–ε-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 ε-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.

中文翻译：

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铁碳相的碳化物区的相平衡

摘要

在碳化物区域（渗碳体线的右边），Fe-C相图的主要演变阶段是最近讨论的理论话题。已经确定的是先前分离的ε -铁₂ C，χ -铁₅ Ç ₂和g-的Fe ₇ Ç _3个碳化物（除渗碳Θ -铁₃ C）是化学计量的化合物。因此，它们是可变组成的相，包含基于配尔顿类和伯醇类的化学计量组成或第二类间隙固溶体。已经指出，铁渗碳体相图可被标识为铁的ε-Fe ₂在0-9.7％C.以下的相变的浓度范围C碳化物相图被引入到图：渗碳Θ -铁的非变体同熔平衡的反应₃以下结晶; 碳化物的包晶平衡的反应χ -铁₅ c ^ ₂结晶; 碳化物的低温蠕变转变，铁素体和渗碳体的固溶体形成基于ε-碳化物Fe ₂ C缩合物的均质性较宽的固溶体。已经表明，碳化物相代表均匀的同质准碳化物固溶体，而碳化物相则以准共晶的形式以碳化物相混合物的形式结晶。