Superior work hardening behavior of moderately high carbon low alloy super strong and ductile multiphase steels with dispersed retained austenite

Abstract

The present paper discusses the superior work hardening behavior of a series of newly designed super strong (tensile strength~1100–2000MPa) and highly ductile (elongation~12–32%) multiphase steels comprising of intercritical ferrite, bainite, retained austenite and pearlite in various proportions. This combination of phases has been obtained by continuously cooling a moderately high carbon high silicon steel for various durations in air followed by austempering at different temperatures. Due to excellent response of retained austenite towards strain induced transformation, work hardening behavior of the current steels is observed to be similar to that of expensive austenite based TRIP steels. Room temperature strain hardening exponents of the developed steels are found to be at par with that of the austenite based steels. Effect of various factors, like carbon in retained austenite, volume fraction and grain size of retained austenite, presence of neighboring phases on the susceptibility of the steels towards strain induced transformation is also studied.