Mechanical Behavior and Quantitative Fractographic Characterization of Hot-Stamped Usibor® 1500 Steel as a Function of Strain Rate

Abstract

Effects of strain rate on mechanical behavior and fractographic features are elucidated in Usibor® 1500 hot-stamped at extreme conditions. Uniaxial tensile tests have been performed at strain rates ranging from 10−4 to 103 per second. It is observed that the ductility and ultimate tensile strength are higher at the highest strain rate as compared to the lowest strain rate studied. Unbiased quantitative fractography has been applied to characterize the fracture surfaces after tensile tests. Numerous quantitative fractographic attributes including area fractions of the fractures surfaces generated by different fracture micromechanisms and number density of dimples in the dimpled fracture regions have been estimated from the quantitative fractographic data. These data reveal that ductile dimpled fracture is the dominant fracture micromechanism at all strain rates. Nonetheless, the extent of the fracture surface generated by ductile dimpled fracture increases with increase in the strain rate. Therefore, increase in the strain rate facilitates dimpled ductile fracture or increases resistance to brittle fracture (or both).