High temperature deformation in ultrahigh carbon steels

Ultrahigh carbon steels (UHCS) contain from 1 to 2.1% carbon and have been shown to be superplastic at elevated temperature and strong, tough and ductile in tension at low temperature. The basis for achieving such properties is the ability to prepare these steels with fine ferrite grain sizes (1 to 5 mu m) and fine spheroidized carbides. The elevated temperature mechanical properties of these steels will be described with special emphasis on their behavior at large strains utilizing torsion and tension tests. The influence of carbon content and grain size on the deformation characteristics are considered. The results are discussed on the basis of deformation mechanisms involving grain boundary sliding and diffusion-controlled dislocation creep.