Advanced High Strength Steels (AHSS), bainite, microstructure, mechanical properties, formability, modeling
File number: MAT2016-81031-R
Program: Programa Estatal de I+D+i Orientada a los Retos de la Sociedad
Despite the great development of recent years, the potential of Advanced High Strength Steels (AHSS-) has not been fully exploited. The new steps in optimizing these steels require a systematic approach, combining experimental characterization with simulation based on physical models. To date, much of the work has been devoted to the correlation between the process parameters, the characteristics of the bainitic microstructure, and certain mechanical properties, but current models only predict the transformation kinetics of bainite, and still do not provide information about the morphology of the microstructure. In fact, there is still no microstructure-based model to predict the mechanical behavior of bainite. In addition to all this, very little attention has been paid to the effect that the presence of small martensite fractions or martensite / austenite islands in the matrix can have on strength and formability. However, recent studies indicate that even small percentages of martensite can greatly affect the mechanical and damage properties of bainitic steels.
The objective of the project is to improve the cold formability of advanced high resistance bainitic steels with applications in the automotive industry, by controlling second phases and optimizing the microstructure. This involves combining high tensile strength with adequate ductility and good behavior under orifice expansion test conditions. In bainitic microstructures, the presence of second phases such as martensite or retained austenite play a crucial role, although the subject has so far been little studied. Knowledge of microstructural transformation mechanisms and deformation and damage processes may allow better control of these properties. As a result of the project, guidelines will be defined for the production of advanced high resistance bainitic steels (Bainitic AHSS) with optimal properties.