Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties

Abstract In this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed quenching. Decreasing the IHT temperature from to leads to: (i) a decrease in volume fraction of austenite (martensite after quenching) 0.68 0.36; (ii) ~ 100 martensite start (Ms), mainly due higher carbon content its smaller grains °C; (iii) reduction block size 1.9 1.2 μm as measured EBSD. Having finer size, localized microhardness islands increases 380 HV (800 °C) 504 (750 °C). Moreover, despite different fractions DP microstructures, hardness steels remained unchanged changing (~ 234 238 HV). Applying lower (lower martensite), impact energy even decreased 12 9 J brittleness phase. The results tensile tests indicate that increasing temperature, yield ultimate strengths steel increase 493 770 MPa, 908 1080 respectively, while total elongation decreases 9.8 4.5%. contrast normalized sample, formation could eliminate point phenomenon curves, it generates free dislocations adjacent ferrite.