A low-cost strategy to improve strength-ductility-toughness balance in a low-carbon steel

The current research introduces a low-cost strategy to improve strength-ductility-toughness balance in low-carbon steel containing 0.08 wt-% carbon by simple heat treatment. As the intercritical annealing temperature increased, the fraction of martensite enhanced. By increasing the annealing temperature from 770 to 830 degrees C, the hardness of dual-phase steel was increased from 183 HV to 212 HV, which was due to the increment of martensite fraction from 0.28 to 0.49. The strength of all dual-phase steel samples produced by intercritical annealing treatment was higher than that of the initial sample owing to the presence of hard martensite in the soft ferrite. The interesting point was that the ductility of the dual-phase steels was almost the same as the initial sample. This led to a remarkable increase in the toughness of dual-phase steels compared to the initial sample. All dual-phase steels revealed a perfect ductile fracture.