Mechanical properties of cementite

Abstract

This review focuses on the mechanical properties of cementite as a single phase. The mechanical properties of interest are 1) sound velocity, 2) elastic constants, 3) hardness, 4) plastic deformation mechanism, 5) wear, 6) fracture toughness, and 7) crystal orientation anisotropy. The effect of temperature, magnetic transition and alloying element on sound velocity, elastic constants and hardness were reviewed. Experimental values of the above mechanical properties were collected together with the specimen shape, the amount of alloying elements, the measurement method, etc. A large variation was found in the reported experimental values. The main reason for this is that cementite is metastable and it is difficult to prepare large single-phase samples. Other factors such as sample shape, measurement method, alloying element, magnetic transformation, and crystal orientation anisotropy also influenced the measured values. The studies using the first-principles calculation on cementite were also reviewed. The crystal orientation anisotropy of the elastic constant of single crystal cementite based on the first-principles calculation was summarized and its comparison with experiment was discussed. Comparing the elastic constants obtained by the first-principles calculation with the measured values, the former values are several % to several tens of % larger than the latter values. The cause of this is thought to be the difference in temperature between 0 K (first-principles calculation) and room temperature (measured value), and theoretical and experimental researches in which the temperature is changed are expected.