Fatigue life behaviour of the dual-phase low carbon steel sheets

This paper presents the effect of heat treatment on the fatigue life of low carbon steel sheet with dual-phase microstructure. The steel sheets were heat treated with two different procedures; intermediate quenching, intermediate quenching and tempering. The properties of tensile strength, fatigue life, hardness, micro hardness and microstructure were evaluated by the mechanical tests and metallographic analysis, respectively. The results showed that dual-phase steel (DPS) microstructures, composed by ferrite and martensite had higher fully reversed plane bending fatigue strength when compared with as-received steel and tempered martensite (TM) steel. The experimental results showed that fatigue life of the heat-treated steel sheets enhanced with increasing amount of martensite in the microstructure. The highest fatigue strength was observed on the intermediately annealed steel sheets at 870 °C. Internal microstructures, fatigue crack initiation and propagation of the heat-treated steel were analyzed by scanning electron microscopy (SEM).