ABSTRACT Cementite occurs in steels, in meteorites, possibly at the core of the Earth and has uses in its pure form. It's composition can deviate from , but not by much because the Fe–C bond contributes to its cohesion. Its crystallographic unit cell is orthorhombic and primitive, with large lattice parameters, explaining its hardness. Many of its properties are anisotropic. Its single-crystal elastic properties have been investigated using first-principles calculations and by clever experiments. The iron atoms in the cell occupy two types of positions with different point symmetries; the four carbon atoms lodge within prismatic interstices. The structure can develop defects such as dislocations, faults and vacancies. Cementite is metallic and ferromagnetic with a Curie temperature of about 187C. When alloyed, metallic solutes substitute on to the iron sites; smaller atoms such as boron replace carbon at interstitial sites. This review focuses on cementite as a single phase.

中文翻译：

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渗碳体

摘要 渗碳体存在于钢、陨石中，可能位于地球的核心，并以其纯净的形式使用。它的成分可能会偏离 ，但不会偏离太多，因为 Fe-C 键有助于其内聚力。它的晶体晶胞是正交和原始的，具有大的晶格参数，解释了它的硬度。它的许多特性是各向异性的。已经使用第一性原理计算和巧妙的实验研究了它的单晶弹性特性。晶胞中的铁原子占据两种不同点对称性的位置；四个碳原子位于棱柱形空隙中。该结构会产生缺陷，例如位错、断层和空位。渗碳体是金属和铁磁性的，居里温度约为 187C。合金化时，金属溶质替代铁位点；较小的原子（如硼）在间隙位置取代碳。本综述重点关注渗碳体作为单相。