Thermo-kinetics of carbon ordering in carbon-supersaturated iron

抄録

Carbon ordering in supersaturated iron is known to induce the tetragonality of the martensite lattice. According to Zener and Khachaturyan, the ordering is determined by strain-induced carbon-carbon interactions. Carbon ordering is probably responsible for the nanostructuring of martensitic microstructures and the resulting high mechanical strength of Fe-C martensite. Understanding the role of carbon content, temperature and applied stress on carbon ordering necessitates the investigation of various phenomena related to carbon migration in the lattice, down to the atomic scale. In this article, we present a unified theoretical treatment of the thermodynamics and kinetics of carbon ordering applicable to ferrite and martensite phases. Our results are based on a mean-field thermo-kinetic model integrating long-range elastic carbon-carbon interactions. All parameters of the model originate from ab initio calculations. Various phenomena such as the effect of stress on the ordering, the thermo-elastic behavior, the anisotropy of carbon diffusion, the internal friction response and the carbon clustering in supersaturated carbon alloys are discussed.