Carbon content of retained austenite in quenched steels

H. K. D. H. Bhadeshia

Abstract

Much effort has recently been directed towards the determination of the carbon concentration of retained austenite in directly quenched, or quenched and tempered martensitic steels. The results show that the concentration may be significantly larger than the average concentration in the alloy concerned. The interpretation of such data is difficult, but the present paper is concerned with the possibility that some redistribution of carbon may occur during the transformation of austenite to what is generally referred to as lath martensite. Thermodynamic analysis has been used to show that the experimental data are not consistent with diffusion occurring during transformation.

This scientific communication examines how carbon levels fluctuate within retained austenite during the cooling and tempering of low alloy steels. The researcher investigates the thermodynamic limits of carbon redistribution, specifically focusing on whether the element moves during the formation of lath martensite. By utilizing free energy curves and tie-line constructions, the text explains that certain chemical concentrations at the interfaces dictate the transformation speed and stability. The study compares calculated values against experimental data to determine if the growth process is strictly diffusionless or involves partial carbon movement. Ultimately, the findings suggest that the enrichment of austenite likely occurs during the actual growth phase of martensite rather than solely through subsequent processes.

Metal Science, Vol. 17, 1983, pp. 151-152.

Download PDF file of paper

Audio podcast Podcast about the work