J032 Change in microstructure and mechanical properties with low-temperature tempering in retained austenite included martensitic carbon steel

摘要

The hardness of as-quenched Fe-0.3%C alloy increases during low-temperature tempering at 373 K due to finely dispersed metastable carbides 1). On the other hand we reported that as-quenched Fe-0.3%C-10%Ni alloy including retained austenite (retained γ) is never hardened but softened continuously during tempering in the previous study 2). These results suggest that of the solid solution strengthening in martensite matrix significantly exceeds the effect of the precipitation strengthening by not only precipitation of metastable carbides but also carbon partitioning into retained y Thus, the carbon partitioning into retained y occurs markedly even at low-temperature tempering so that the strength-toughness balance may be improved in martensitic carbon steels when they are applied low-temperature tempering treatment In this study, microstructure and mechanical properties characterization were carried out in low-temperature tempered Fe-0.3%C-10%Ni alloy in order to clarify the effect of carbon partitioning on its microstructure, strength, ductility, and toughness.