Probing the Characteristic Deformation Behaviors of Transformation-Induced Plasticity Steels

The characteristic micromechanical behaviors of contrasting transformation-induced plasticity (TRIP) steels were investigated under tensile loading by in-situ neutron diffraction and transmission electron microscopy in detail. As demonstrated by the lattice strain development from the neutron diffraction, in the TRIP steel with ∼10 pct RA, microyielding of soft ferrite was responsible for the first stress partition, but a second stress sharing was caused by effective martensitic transformation. In the TRIP steel with less than 5 pct RA, where the contribution from the martensitic transformation was minor, stress partition took place virtually between the ferrite and bainite phase. Probing with systematic transmission electron microscopy (TEM) observations, we pin down the inherent correlation between the microstructural evolutions and the stress partition mechanism. Based on the experimental observations, the factors influencing the work-hardening behavior of TRIP steels are discussed. This article is based on a presentation given in the symposium entitled “Neutron and X-Ray Studies for Probing Materials Behavior,” which occurred during the TMS Spring Meeting in New Orleans, LA, March 9–13, 2008, under the auspices of the National Science Foundation, TMS, the TMS Structural Materials Division, and the TMS Advanced Characterization, Testing, and Simulation Committee.