Abstract:
Due to rigid environmental laws and the fuel efficiency goals stipulated by the Federal Government, automakers seek new processing routes to reduce the mass of vehicles without compromising their mechanical strength. The most widely used is hot stamping of boron steels. However, after this process the steel does not have sufficient ductility to absorb energy during impact. Hence, the quenching and partitioning cycle (Q&P) has been recently proposed to recover the ductility through carbon partitioning from martensite to austenite (γ), which favors the transformation induced plasticity effect. This work discusses the effects of percentage of applied deformation and the partitioning temperatures on the carbon enrichment of γ, using synchrotron radiation in-situ, in a Gleeble 3S50TM thermomechanical simulator. Deformations in 10%, 20% and 30% at high temperatures, as well as partitioning temperatures of 260 °C, 300 °C and 340 °C were applied. Electronic microscopy, X-ray diffraction, microhardness and sub-size tensile test techniques were employed to characterize the samples. The results suggest that increasing the applied deformation increases the time required for maximum carbon partitioning. Similarly, as the partitioning temperature increases, the time of maximum partitioning is strongly increased. Therefore, it is concluded that 10% of deformation and 260ºC of partition temperature are the most appropriated parameters to minimize partitioning times.