Impact-dynamic behaviour of Al-TRIP steel

In recent years TRIP-steels (TRansformation Induced Plasticity-steels) have been developed. TRIP-steels are composite steels composed of ferrite, bainite and retained austenite. During plastic deformation, the austenite phase transforms to martensite, and this gives rise to an exceptional mechanical behaviour of the material: high strength levels (yield strength, tensile strength, .) are combined with an excellent ductility. The resulting high energy dissipation makes TRIP-steels extremely suitable for energy-absorbing devices such as the bars used in the crumpling zone of a car. To guarantee a controlled dissipation of the energy released during a crash, knowledge and understanding of the impact-dynamic material properties is essential. In this contribution results of an extensive experimental program to investigate the strain rate dependent mechanical properties of a TRIP-Al-steel are presented. A split Hopkinson tensile bar set-up was used for the experiments. Next to the TRIP-material, also the three constituent phases of the TRIP-steel were produced and subjected to high strain rate loading. From the results it is clear that TRIP steels, also in dynamic circumstances, show excellent mechanical properties.