KINETICS AND MICROSTRUCTURAL EVOLUTION DURING ISOTHERMAL BAINITIC TRANSFORMATION

摘要

Kinetics and microstructural evolution during isothermal bainitic transformation in SAE 52100 bearing steel, 1.01C-1.36Cr-0.32Mn-0.25Si (wt.%), are investigated. The kinetics (the fraction of bainite as a function of holding time) is measured with dilatometry at various temperatures and the microstructural evolution during the bainite transformation at 503 K is characterized based on the results from magnetic measurements, x-ray diffraction and optical microscopy. The volume fraction of existing phases at room temperature, bainite, carbide, retained austenite and martensite, are quantitatively determined, in which the martensite is formed from the least stable fraction of austenite during quenching from 503 K.