Varnita Bajpai , IDD, Metallurgical Engg., IIT (BHU), Varanasi (INDIA) (original) (raw)

Papers by Varnita Bajpai , IDD, Metallurgical Engg., IIT (BHU), Varanasi (INDIA)

Proceedings of CHT-17 ICHMT International Symposium on Advances in Computational Heat Transfer May 28-June 1, 2017, Napoli, Italy, 2017

In this work, continuous casting process of a billet caster has been simulated using a simple, bu... more In this work, continuous casting process of a billet caster has been simulated using a simple, but comprehensive mathematical model. The solidification process is modelled through finite-difference calculations of heat conduction within the solidifying steel shell which give thermal gradients and columnar front velocity along the billet mid-plane. In order to account for bulk convection due to the submerged-entry nozzle, an effective thermal conductivity within the mush is defined under the solid-liquid coexisting zone theory. The model predicts solidified shell thickness, local solidification time, metallurgical length and two important microstructural parametersprimary and secondary dendritic arm spacings (PDAS and SDAS)which are used to characterize inclusion redistribution during solidification. Inclusion-front interaction is modelled using a dynamic formulation that calculates the critical velocity for pushing or engulfment as a function of particle size and factors in the differences in thermal properties of particle and melt. Pushing of inclusions larger than the estimated PDAS and entrapment of inclusions smaller than SDAS is also considered.

In this study Mo-Nb-Ta-W refractory high-entropy alloys (R-HEAs) have been studied for their phas... more In this study Mo-Nb-Ta-W refractory high-entropy alloys (R-HEAs) have been studied for their phase stability for a wide temperature range (100 K to 2000 K). The equilibrium thermodynamic phases are determined by the changes in enthalpy and entropy. The enthalpy changes at any temperature are simulated by embedded atom method (EAM) potential based hybrid Monte Carlo molecular dynamics (MC/MD) simulations. Configurational entropy was calculated by quasichemical method. The EAM potentials were all calculated based on the physical input parameters of elements like atomic volume, cohesive energy, elastic constants etc. It was found that the MC/MD evolved equilibrium structures and the degree of local chemical short-range order/clustering (SRO/SRC) largely depend on the ordering enthalpies for various temperatures. The ordering transition temperature is close to 700 K, which is also substantiated by the experimental powder X-ray diffractions done in synchrotron beam. Large increase of deg...

Proceedings of CHT-17 ICHMT International Symposium on Advances in Computational Heat Transfer May 28-June 1, 2017, Napoli, Italy, 2017

In this work, continuous casting process of a billet caster has been simulated using a simple, bu... more In this work, continuous casting process of a billet caster has been simulated using a simple, but comprehensive mathematical model. The solidification process is modelled through finite-difference calculations of heat conduction within the solidifying steel shell which give thermal gradients and columnar front velocity along the billet mid-plane. In order to account for bulk convection due to the submerged-entry nozzle, an effective thermal conductivity within the mush is defined under the solid-liquid coexisting zone theory. The model predicts solidified shell thickness, local solidification time, metallurgical length and two important microstructural parametersprimary and secondary dendritic arm spacings (PDAS and SDAS)which are used to characterize inclusion redistribution during solidification. Inclusion-front interaction is modelled using a dynamic formulation that calculates the critical velocity for pushing or engulfment as a function of particle size and factors in the differences in thermal properties of particle and melt. Pushing of inclusions larger than the estimated PDAS and entrapment of inclusions smaller than SDAS is also considered.

In this study Mo-Nb-Ta-W refractory high-entropy alloys (R-HEAs) have been studied for their phas... more In this study Mo-Nb-Ta-W refractory high-entropy alloys (R-HEAs) have been studied for their phase stability for a wide temperature range (100 K to 2000 K). The equilibrium thermodynamic phases are determined by the changes in enthalpy and entropy. The enthalpy changes at any temperature are simulated by embedded atom method (EAM) potential based hybrid Monte Carlo molecular dynamics (MC/MD) simulations. Configurational entropy was calculated by quasichemical method. The EAM potentials were all calculated based on the physical input parameters of elements like atomic volume, cohesive energy, elastic constants etc. It was found that the MC/MD evolved equilibrium structures and the degree of local chemical short-range order/clustering (SRO/SRC) largely depend on the ordering enthalpies for various temperatures. The ordering transition temperature is close to 700 K, which is also substantiated by the experimental powder X-ray diffractions done in synchrotron beam. Large increase of deg...