Abstract:Hans-Jürgen ChristInstitute for Materials Science -University of Siegen / Germany. E-mail: crist@ifwt.mb.uni-siegen.de
Ulrich KruppApplied University of Osnabrück / Germany. E-mail: u-krupp@fh-osnabrueck.de
ResumoUma previsão razoável da durabilidade de estruturas ou equipamentos que operam em temperaturas elevadas e atmosferas agressivas requer um completo entendimento dos mecanismos de degradação dos materiais causados por cargas mecânicas e corrosão. O objetivo geral desse estudo é simular processos de corr… Show more
“…where D O is the diffusion coefficient of oxygen, t is the specific simulation time and γ an appropriate kinetics parameter that can be calculated via use of the diffusion equations [11,17,18] seen above. The region 0 > x > ξ(t), known as the oxidation zone, is where the oxygen diffusion is confined.…”
A numerical model is presented to simulate the diffusional transport of oxygen and that of an alloying element, within a 1-D binary Ni alloy, leading to the selective oxidation of the alloying element and the formation of an internal oxide precipitate. This specific model is written in MATLAB and, with the aid of the Matlab Toolbox, is coupled to the ThermoCalc extensive database. A reaction time is introduced to overcome problems related to the difficulty of formation of the internal oxide. Two cases are considered: Al as the alloying element for which the solubility product of the oxide forming elements is small, and Mn for which it is large.
“…where D O is the diffusion coefficient of oxygen, t is the specific simulation time and γ an appropriate kinetics parameter that can be calculated via use of the diffusion equations [11,17,18] seen above. The region 0 > x > ξ(t), known as the oxidation zone, is where the oxygen diffusion is confined.…”
A numerical model is presented to simulate the diffusional transport of oxygen and that of an alloying element, within a 1-D binary Ni alloy, leading to the selective oxidation of the alloying element and the formation of an internal oxide precipitate. This specific model is written in MATLAB and, with the aid of the Matlab Toolbox, is coupled to the ThermoCalc extensive database. A reaction time is introduced to overcome problems related to the difficulty of formation of the internal oxide. Two cases are considered: Al as the alloying element for which the solubility product of the oxide forming elements is small, and Mn for which it is large.
“…Calphad (Dinsdale, 1991) method allows the theorectical modelling of phase diagrams taking advantage of the current development of powerful computers and sophisticated softwares. A powerful commercial software using the Calphad methodology is the FactSage (Bale et al, 2002;Trindade et al, 2009), which was used in this work for the thermodynamics calculations for the binary Al-Si, Fe-Al and Fe-Si systems as well as the ternay Fe-Al-Si and quaternary Fe-Al-Si-O systems.…”
High-strength steels are commonly used in the automobile industry in order to reduce the weight of the vehicles. However, a technical difficulty appears due to the need of hot stamping of the components, which leads to oxidation. Therefore, the application of a coating on the substrate to avoid high-temperature oxidation is used. In this work, experimental analysis and computer thermodynamic calculation were used to describe the phase transformations within an Al-Si coating on a quenchable high strength steel. The Al-Si coating was deposited by hot dipping and its characterization was done using SEM and XRD techniques. Computer thermodynamics calculations were done using the commercial software FactSage using the Calphad methodology. It demonstrated a good relationship between the experimental results and the computer calculations of phase stabilities for the as-deposited condition and after diffusion experiment at 920 o C for 7 minutes, which simulates the thermal cycle of hot stamping of the quenchable steel used.Keywords: Al-Si coating, hot stamping, computer thermodynamics, interdiffusion, ultra-high-strength steel.
Vicente Braz Trindade
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