Research Projects

Abstract: Extensive studies have been performed on the microalloy precipitates in steels by the Indian industries and academia. However, detailed investigation on the chronological stages of precipitation, starting from the atom clusters, GP zones to metastable phases and finally stable precipitate phase and the corresponding evolution of size, morphology, structure, composition and stoichiometry of the precipitates in steels have hardly been studied in India. That sets of objectives of the proposed project as listed in next section. The global research interest on atomic cluster strengthening in addition to precipitation strengthening emerged a possibility of developing even higher strength steels than that can be achieved relying solely on precipitation strengthening. The effects of atomic clusters along with the precipitates on other properties such as ductility and toughness may be need to be explored. The proposed project aims to perform a detailed investigation on the precipitates, their evolution and effects in microalloyed steels by involving at one side the thermal and thermomechanical processing, precipitate characterization, and mechanical property assessment and on the other side study of thermodynamic and kinetic aspects of precipitation, first-principles calculations on precipitate stability and MD and DD based simulations of dislocation-precipitation interaction. Objectives: • To thoroughly characterize the NbC, NbN, and Nb(C,N) precipitates in Nb microalloyed low-C steels and understand the stages of evolution starting from atom clusters, GP zones, metastable precipitates to stable precipitates. • Particular emphasis to be laid on the evolution of atomic ratios and compositions within the atom clusters and precipitates (the precipitate stoichiometry), including the concentration of Fe atoms and vacancies. • Density functional theory (DFT) based calculation to understand the atomic structure (including the vacancies) and composition (including the solubility of Fe) of precipitates. • At present, a clear thermodynamic and kinetic basis of the evolution of atom clusters and precipitates is missing. The proposed study aims to establish that. • Finally, the interaction between atom clusters and precipitates with dislocations will be characterized and simulated. Major Activities: Steel melting, Thermal and thermomechanical processing, Precipitate characterization, Thermodynamic and kinetic calculations, DFT based first-principles calculation, MD and DD based simulations on precipitate-dislocation interactions, Assessment of bulk mechanical properties like hardness, strength, ductility and impact toughness. Project duration: Three (3) years Proposed Budget: INR 74,71,200/- (the entire fund is requested to be given to IIT Kharagpur)

Atom-clusters precipitates