Modelling of the Mechanical Properties of Low Alloyed Multiphase Steels with Retained Austenite Taking into Account Strain-Induced Transformation

The objective of this work is to understand the correlations between the microstructure and the mechanical properties of modern high strength multiphase steels with retained austenite (RA-steels) on a microstructural level and to describe them by models quantitatively. In addition, special attention is paid to the course and the influence of the strain-induced transformation of the retained austenite to martensite. To achieve this target, the literature was intensely evaluated and moreover, an extensive experimental investigation program was carried out. As test materials industrially manufactured hot and cold rolled multiphase steels were chosen. On the basis of the test results a mathematical model for the numerical description of the kinetics of the strain-induced transformation was set up. Then under use of a recently published rule of mixture a model system to calculate the flow curve of RA-steels was developed. It takes into account the strain-induced transformation. For the strain region above ɸ = 0.03 the calculated flow curve agrees well with the measured values, so that an application of the model system is possible in the practice of steel development and steel manufacturing.