Tuning strength-ductility combination of AISI 1008 steel through large strain single-roll drive rolling and intercritical annealing

Abstract

In this study, the influence of large-strain single-roll drive rolling and intercritical annealing on the microstructure evolution and mechanical behavior of AISI 1008 steel was investigated. The microstructures of all fabricated dual-phase (DP) steels exhibited equiaxed and homogeneously distributed fine ferrite grains and martensite islands. Compared to the as-received sample, the hardness of the produced dual-phase steels increased by up to 100%. As the temperature of intercritical annealing treatment increased, the hardness of the dual-phase samples increased from 233.2 HV to 258.4 HV. All fabricated DP steels showed much higher strength and toughness than the as-received sample. Overall, with increasing the temperature of intercritical annealing, the strength, ductility, and toughness of DP steels were improved due to increasing the martensite fraction. Also, by increasing the temperature of intercritical annealing from 770 to 860°C, the work hardening rate of the DP sample was enhanced. The hardness and strength of dual-phase steels had a good linear correlation to the fraction of martensite. The failure mechanism of the 80% rolled sample was mainly brittle while all DP samples exhibited a perfect ductile fracture characterized by many homogeneous deep dimples without any cleavage facets.