An investigation on the deformation mechanisms of high carbon steel under the influence of thermal and rate-dependent loading

Abstract

In this paper, the effect of strain rates on the material and substructural behaviour of high carbon (1% C) steel (HCS) is experimentally investigated at ambient and elevated temperatures. Compression tests at different strain rates (2.56 × 10-4 - 2.56 × 10-1/s) as well as temperatures (25-175 °C) were performed and the corresponding structure-property correlations were established. The material exhibited transformation of austenite to martensite at ambient condition whereas formations of ferrite/tempered martensite (TM) and carbide precipitates were evidenced at higher temperatures. At the high-temperature regime, with increasing the temperature from 100 to 175 °C, a noticeable increase in yield strength is evidenced. Such an increase in yield strength is due to the increase in the volume fraction of carbides precipitation and dislocation strengthening associated with the phase transformation. An overall increase in the kernel average misorientation (KAM) values were found with an increase in the strain-rate whereas, in terms of increasing temperature, the lowest KAM values were exhibited when the material was deformed at 100 °C. Transmission electron microscopy (TEM) studies revealed decreasing dislocation cell size with increase in the temperature and strain rate that further indicates an increase in the dislocation density of the material. The width of the plate martensite displayed a declining trend with a rise in the strain rate irrespective of the deformation temperature.