TY - THES

T1 - Ab initio calculations of alloying impact on structural properties and stability of cementite

AU - Sakic, Amin

N1 - no embargo

PY - 2020

Y1 - 2020

N2 - The longstanding search for suitable materials for the automotive industry, which should both increase passenger safety and reduce fuel consumption and thus CO2 emissions, has led to the development of the TBF and Q&P steels. These steels are alloyed with silicon to prevent cementite precipitation from the austenite. This stabilizes the austenite with higher carbon content and enables the TRIP effect. Based on density functional theory (DFT) calculations within the generalized gradient approximation (GGA), the influence of silicon and aluminum on the stability of cementite is theoretically assessed in this thesis. Namely, the influence of the alloying elements on the formation and partitioning enthalpy is examined. The elastic constants and the bulk and shear moduli using the Voigt-Reuss-Hill method are calculated and the directional dependence of the Young's modulus is investigated. Finally, the influence of the alloying elements on the local electron structure is analyzed in terms of the density of states and charge density.

AB - The longstanding search for suitable materials for the automotive industry, which should both increase passenger safety and reduce fuel consumption and thus CO2 emissions, has led to the development of the TBF and Q&P steels. These steels are alloyed with silicon to prevent cementite precipitation from the austenite. This stabilizes the austenite with higher carbon content and enables the TRIP effect. Based on density functional theory (DFT) calculations within the generalized gradient approximation (GGA), the influence of silicon and aluminum on the stability of cementite is theoretically assessed in this thesis. Namely, the influence of the alloying elements on the formation and partitioning enthalpy is examined. The elastic constants and the bulk and shear moduli using the Voigt-Reuss-Hill method are calculated and the directional dependence of the Young's modulus is investigated. Finally, the influence of the alloying elements on the local electron structure is analyzed in terms of the density of states and charge density.

KW - TBF and Q&P steels / Cementite / Ab initio calculations / Impact alloying elements on cementite / Structural properties / Stability

KW - TBF- und Q&P-Stähle

KW - Zementit

KW - Ab-Initio-Berechnungen

KW - Auswirkungen von Legierungselementen auf Zementit

KW - Struktureigenschaften

KW - Stabilität

M3 - Master's Thesis

ER -