PHASE TRANSFORMATIONS IN INTERSTITIAL FREE AND LOW DENSITY STEELS

Abstract

The interstitial-free (IF) steel is extremely soft and ductile. The strengthening is the key focus of the present study by heat treatment. The samples have been soaked in the austenitic temperature domain followed by different rates of cooling (furnace cooling, air cooling and water quenching) in a Gleeble 3800® thermo-mechanical simulator. The outcome exhibits a dramatic improvement in strength as compared to reported conventional techniques. The electron microscopy along with EBSD has characterized lath martensite in this commercial grade steel. The hot deformation of austenite to martensite has also been investigated to study constraints in the martensite formation with variant selection in the present alloy system as well for a comparative study. The structure-property correlation is the key ingredient to address the role of the hierarchical structure (block and sub-block boundaries) against microstructural morphology for the obtained mechanical properties. In the additional part of the present work, some calculation with Dictra simulation has been performed to study phase transformations in low density steel. It is known that Al as the alloying element is inevitable for density reduction of steels. It in turns produces δ-ferrite in the system. The consequence of δ-ferrite to the austenite formation is the key theme in this part of work