Structure-Property Correlations of a Medium C Steel Following Quenching and Isothermal Holding above and below the M<sub>s</sub> Temperature

The processing of advanced multiphase high strength steels often includes isothermal treatments around the martensite start temperature (Ms) for achieving a refined microstructure comprising bainite-austenite and/or bainite-martensite-austenite phase constituents. objective this research work was to investigate structure-property relationship medium carbon, high-silicon DIN 1.5025 steel (Fe-0.529C-1.67 Si-0.72Mn-0.12Cr (in wt.%)) following holding close Ms (~275°C) enable low austenite decomposition. For realizing microstructures, samples were austenitized at 900°C 5 min and then quenched temperatures 350 250°C various times ranging from 3600 s. Microstructural investigation corroborated formation tempered martensite, bainite, retained austenite, fresh in both isothermally held above (350°C) below (250°C) temperature. sample showed much more comparison that 350°C due presence fraction initial laths which acted as potential sites bainite nucleation. Also, evaluation mechanical behaviour best tensile properties terms good ductility achieved with volume fractions interlath blocky particularly those treated 200 s 600 s, respectively.