Rate-dependent mechanical strength and flow behaviour of dual-phase high carbon steel at elevated temperatures: An experimental investigation

High carbon low alloy steel with dual phase structures of austenite and martensite is widely used in mining industries for grinding. Such applications of this material undergo deformations due to varying strain rates as well as temperatures. This paper is aimed to understand the rate dependent flow behaviour of high carbon steel at different regimes of operating temperatures. Compression tests were performed over a wide range of strain rates (2.56 x 10(-4) to 2.56 x 10(-1)/s) at different temperatures (25-175 degrees C) and the subsequent physical changes in the fracture surfaces were critically examined. Apart from the variation in yield strength and ductility, the effect of strengthening mechanisms on the strain hardening behaviour of the material was also investigated. The strain hardening rates were observed to be decreasing with an increase in the effective stress values for all the strain rates as well as temperature. Austenite to martensite transformation was observed at room temperature whereas formation of ferrite and cementite were noticed at elevated temperatures. Fracture surfaces revealed the presence of transgranular and intergranular cracks for the specimen deformed at low (2.56 x 10(-4)/s) and high (2.56 x 10(-1)/s) strain rates respectively under ambient conditions. At elevated temperatures, parabolic dimples and microvoids were observed indicating a plastic mode of deformation in addition to the formation of carbide precipitates.