Synergistic Investigations of Post-Deformation Annealing and Initial Microstructure on the Mechanical Properties of High Strength Low Alloy (HSLA)-100 Steel

A high strength low alloy (HSLA)-100 steel with different initial microstructures (ferrite and martensite) is processed by cold rolling at room temperature to the reduction of thickness about 70%. It is found that the recrystallization kinetics of the sample with a martensitic microstructure is higher than the sample with a ferritic microstructure. Moreover, the results show that the partitioning factor of substitution alloying elements is less effective than the strain in the martensitic phase transformation. Also, hardness results show that the samples with a martensitic microstructure have drastic drop compared with the samples with a ferritic microstructure, which is related to continuous recrystallization. Remarkable ultimate tensile strength and elongation to failure (829 MPa and 27.7%, respectively) are achieved for cold-rolled martensite after tempering at 625 degrees C for 360 min. Accordingly, it is also found that the reason for remarkable mechanical properties is the simultaneous presence of recrystallized fine-grained and deformed martensite, which forms an inhomogeneous microstructure.