The influence of austenisation on the kinetics of tempering—Mössbauer effect study

The Mössbauer effect in ⁵⁷Fe is used to investigate the kinetics of carbide precipitation in plain carbon steel. The investigated carbides were extracted chemically after the steel had been treated at various austenisation and tempering temperatures. The relative amount of cementite precipitated after a certain heat treatment was determined from the spectral area. The activation energy of the process is found to be 0.3 eV. A formula is suggested for the dependence of carbide formation rate on the austenisation temperature.It is found that in the process of the chemical extraction, amorphous iron gel or oxyhydroxide isomers form, rather than iron oxides. The effective internal field H_n and the isomer shift of the extracted carbides depend on the tempering temperature, while the carbide formation rate depends on the austenisation temperature as well.This research is sponsored by the USA National Bureau of Standards Grant No. G-87 (1968).In partial fulfilment of the requirements for the D.Sc. degree.