Abstract: Heightened automobile fuel economy standards necessitate development of economically viable sheet steels with exceptional mechanical properties. The quenching and partitioning (Q&P) heat treatment is designed to create carbon-enriched metastable austenite, which transforms to martensite during deformation, and leads to enhanced strength and ductility. During industrial forming operations, deformation temperatures tend to diverge from ambient conditions, and strain rates tend to exceed quasi-static rates (>0.001 s-1). In this study, tension testing of Q&P steels at strength levels of 980 and 1180 MPa was performed at strain rates from 0.0001 to 0.1 s-1, while adiabatic heating was evaluated using thermocouples and thermal imaging. Scanning electron microscope fractography was used to identify a mechanism for ductile failure, and retained austenite was measured with x-ray diffraction to evaluate the extent of austenite transformation.
Authors: Christopher Finfrock, Gus Becker, Trevor Ballard, Grant Thomas, Kester Clarke, and Amy Clarke
Keywords: Transformation-induced plasticity, AHSS, Dynamic tensile testing, Adiabatic heating, Fracture