Tempering of Low–Temperature Bainite

Abstract

Electron microscopy, X-ray diffraction and atom probe tomography have been used to identify the changes which occur during the tempering of a carbide free bainitic steel transformed at 200◦C. Partitioning of solute between ferrite and thin-films of retained austenite was observed on tempering at 400◦C for 30min. After tempering at 400◦C and 500◦C for 30min cementite was observed in the form of nanometre scale precipitates. Proximity histograms showed that the partitioning of solutes other than silicon from the cementite was slight at 400◦C and more obvious at 500◦C. In both cases the nanometre scale carbides are greatly depleted in silicon.