Experimental and finite element comparison of mechanical properties and formability of dual phase steel and ferrite - pearlite steel with the same chemical composition

Ferrite - martensite dual-phase (DP) steels are a subset of advanced high strength steels which can be produced by applying heat treatment on low-carbon steels. The strength and toughness of DP steels are greater than those in ferrite – pearlite steels with the same chemical composition. In this study, mechanical properties and forming limit diagram of ferrite – pearlite and DP steels with the same chemical composition were investigated and compared. For this purpose, inter-critical quenching heat treatment was applied on a low-carbon steel with ferrite – pearlite microstructure to produce ferrite – continuous martensite DP steel. Tensile and hardness tests were used to determine the mechanical properties, and Nakazima test was used to determine the formability of ferrite – pearlite and DP steels. Forming limit diagram of steels was also simulated using finite element method in macro scale, and compared with experimental results. The results of mechanical tests showed that the yield stress, tensile strength and hardness of produced DP steel were increased 65, 91, and 87% respectively, in comparison to the same mechanical properties of ferrite – pearlite steel. Based on Experimental and simulation results of Nakazima test, the formability of DP steel is better than ferrite – pearlite steel. There was good agreement between simulation and experimental results.