Fatigue of a dual- phase steel

A study has been made of the fatigue of a V containing dual-phase steel, whose tensile strength is equivalent to that of SAE 980X high strength, low-alloy (HSLA) steels, as a function of prestrain. It is found that the cyclic stress-strain curve, strain-life response and notch sensitivity are little affected by pre-strains of up to 8 pct: This is in contrast to monotonie flow strength which increases substantially with prestrain. The fatigue performance of the dual-phase steel, while different in detail from that of other HSLA steels, is intermediate between that for SAE 950X and 980X steels. However, the notch fatigue behavior is equivalent to that of 980X steels. The fatigue response of dual-phase steel can be understood in terms of its high rate of work hardening which is a consequence of its ferrite plus martensite microstructure.