Mechanical properties of nanostructured, low temperature bainitic steel designed using a thermodynamic model

Nanostructured, low temperature bainitic steels with remarkable combination of ultimate tensile strength of about 2.5 GPa and high uniform elongation have been developed in the recent decade. To reduce the production cost of these steels, two chemical compositions were designed by using a thermodynamic model which was developed in Cambridge University by Bhadeshia. To attain optimum mechanical properties, the designed steels were transformed isothermally at the temperature range of 200-300 deg. C for different times. The optimum times for each temperature were estimated by evaluation of hardness and XRD results. The measurements of tensile properties and the fracture surface examination by scanning electron microscopy indicated that by modification of chemical composition the cost production of steel not only reduces, but also the mechanical properties particularly total elongation enhances slightly. The results of this study suggest that by using a thermodynamic model and without try and error it is possible to design a new steel with remarkable combination of mechanical properties.