Austenite formation and mechanical properties of a cold rolled ferrite-martensite structure during intercritical annealing

The austenite formation behavior of 80% cold rolled low carbon steel with ferrite-martensite microstructure during intercritical annealing for different times was studied. Increasing annealing time led to the formation of austenite at the edge of fine recrystallized ferrite grain boundaries. The value of Avrami exponent for the austenite formation was 2 with an activation energy of 90.67 kJ/mol. The variation of hardness, strength and strain-hardening exponent of annealed samples were studied in terms of the microstructural features. The dual phase steel generated by annealing of deformed ferrite-martensite microstructure at 800 °C for 120 s showed a superior strength-elongation balance.