Effect of Intercritical Heat Treatment and Volume Fraction on the Morphological Properties, Mechanical Properties, and Work Hardening Behaviour of Dual-Phase Steel

An investigation aimed at determining the importance of carbon percentage in the microstructure development of dual-phase steel is carried out by intercritically annealing the different samples of low-carbon steels which consists of different percentage of carbon (0.16, 0.18, and 0.20%). The samples are heated in muffle furnace to above Ac3 temperature (920 °C), soaked the sample for 30 min and quenched in ice brine solution to get complete martensitic structure. Later the samples are intercritically annealed at 740, 760, 780, 800, and 820 °C (between Ac1 and Ac3) for 60 min and quenched in oil at room temperature. Microstructure examination revealed that steel containing 0.18%C yields a better microstructure which consists of around 46% martensite and remaining ferrite and minute amount of retained austenite, which is a good combination of strength and toughness. The uniaxial tensile test results show that at specimen containing 0.18%C with 46% martensite content yielded maximum tensile strength with comparatively higher toughness. Microhardness test shows that hardness increases with increasing carbon percentage and has higher values at 0.18%C.