Deformation behavior of an ultrahigh carbon steel (UHCS-3.0Si) at elevated temperature

Isothermal compression tests were carried out on a spray-formed ultrahigh carbon steel (UHCS-3.0Si) by Gleeble 1500 system. The true stress increases with the decrease of temperature and increase of strain rate. The deformation activation energies, Q, of UHCS-3.0Si are not only temperature dependent but also strain rate dependent. The value of Q increases as the deformation temperature decreases and it is in proportion to the weight percent of undissolved carbides. At high deformation strain rates (5–30 s−1), dislocation slip and cross slip are the main deformation mechanism and at low deformation strain rates (0.1–1 s−1), climb-controlled dislocation creep is the main deformation mechanism. Microstructural evolution was analyzed during deformation at 800 °C, cementite lamellas have fair formability and some are broken up which leads to great softening.