Crystallography of in-situ transformations of the M7C3 carbide in the cast Fe–Cr–Ni alloy

Abstract

In the process of holding of the cast heat-resistant Fe–Cr–Ni (0.45C–25Cr–35Ni) alloy at 1150°C, the eutectic chromium carbide present in its structure undergoes a gradual transition M₇C₃ → M₂₃C₆. The gradual formation of domains of the M₂₃C₆ carbide inside the particles of the M₇C₃ carbide makes it possible to assume that the observed phase transition is the well-known carbide transformation of the in situ type. The mechanism of the in situ transformation of the crystal structure of the carbide from M₇C₃ into M₂₃C₆ with a change in the number of nearest metal neighbors of carbon atoms is explained within the previously developed combinatory model of polymorphic transitions in the metals.