Direct measurement of carbon enrichment in the incomplete bainite transformation in Mo added low carbon steels

The overall kinetics and carbon enrichment in austenite during the incomplete isothermal bainite transformation in Fe–0.1C–1.5Mn–(0, 0.03, 0.3, 0.5, 1)Mo (mass%) alloys were investigated with quantitative metallography and Electron Probe Microanalysis in the transformation temperature range of 773–873 K. The incomplete transformation appears at 823–873 K when Mo addition exceeds 0.3 mass%; at 773 K substantial carbide precipitation accompanies bainite transformation and no transformation stasis is observed. Transformed fractions in the stasis stage are hardly affected by prior austenite grain size. Carbon concentrations in austenite in the stasis stage are lower than T0 line and decrease with the increase of Mo addition and temperature. T0′ limit, solute drag and WBs limit theories are used to examine the experimentally measured carbon concentration limits in austenite, and their respective flaws are pointed out.