MICROSTRUCTURE EVOLUTION IN MEDIUM Mn (14 WT.%) HIGH Al (13 WT.%) LOW-DENSITY STEEL

Automobiles are the second largest source of greenhouse gas emissions in the world because of which stringent environmental regulations to control emissions have been incorporated globally in recent years. There is call for weight saving in the body-in-white (BIW) of conventional vehicles and also to compensate the weight of batteries/cells in upcoming Electric/Hybridvehicles. A weight saving of 10% results in 6-8% improvement in fuel economy and eventually reduces emission. As steel comprises, 50-70% weight of vehicle, an approach that can be adopted, is to make the steel lighter without compromising the required mechanical properties. In this context, Al (density=2.7 g/cc) has emerged as the chief alloying element for density reduction in steel. For every 1% addition of Al there is a decrease in density of 1.3% due to combined effect of lower atomic weight and lattice dilatation. An attempt was made to design a suitable steel composition consisting of high Al along with Mn, Ni, C and Si through thermodynamic study in ThermoCalc software and was taken up for the study.