Sara Chentouf - Doctorante
Equipe : Métaux et Alliages
Encadrant : Pr. H. Aourag
e-mail : [email protected]
Equipe : Métaux et Alliages
Encadrant : Pr. H. Aourag
e-mail : [email protected]
Magister en physique
Option: Physique de la Matière Condensée et des Semiconducteurs. Université Abou Bekr Belkaïd de Tlemcen.
Intitulée: Etude de l'efffet des éléments d'addition dans les joints de grain dans le système FeAl. Soutenue en mai 2008.
Intitulée: Etude de l'efffet des éléments d'addition dans les joints de grain dans le système FeAl. Soutenue en mai 2008.
Résumé des principaux résultats
Transition metal impurities have interesting effects on the phase stability in DO3 -Fe3Al, particularly in modifying the transition temperature of this phase towards the B2 one. The fundamental mechanisms responsible of these effects are not clearly understood. This motivates our basic analysis of titanium and zirconium impurities energetic in DO3 -Fe3Al. First principle calculation seems to be the most adapted tool to acquire such an understanding.
Accordingly, systematic and comprehensive study of the alloying impurities effect Ti and Zr on the properties of Fe3Al has been carried out using electronic Density Functional Theory. The total energy has been calculated employing ultrasoft pseudopotentials and the generalized gradient approximation. The impurity formation energies of Ti and Zr are calculated for different configurations both in the bulk material and in grain boundary in DO3 lattice.
A number of conclusions can be drawn from our calculation results. In the following are resumed the most important ones:
(i) In bulk material:
The calculated formation energies correctly predict the experimentally known behavior of Titanium, namely its preference to occupy the FeI site. Zirconium atom presents the same behavior preferring to reside in the FeI lattice site. However, formation energy of this later is greater than that found for titanium. This implies that titanium atoms form stronger bonding with iron atoms than do zirconium ones. Also, vacancies are found to occur more likely on FeII lattice site again in agreement with experiment.
(ii) In grain boundary:
Comparing the impurity formation energies of Ti and Zr at the grain boundary and bulk material, we found that Ti and Zr at grain boundary have the lowest impurity formation energies. We predict that both Ti and Zr prefer to segregate at grain boundary in DO3 -Fe3Al. From energetic point of view, Ti and Zr atoms can lower the grain boundary energy.
So the actions of Ti and Zr at grain boundary play an important cohesive role suggesting that both Ti and Zr reinforce bonds through the grain boundary. This is to be correlated with the previous statement that there exist strong interatomic interactions between Ti and its adjacent FeII atoms. On another hand, Zr-doped grain boundary, it is found that the strong interatomic interactions are between Zr and its adjacent FeI atoms.
In conclusion, our calculation results suggest that the strengthening effect of Ti and Zr in DO3 -Fe3Al originates from the grain boundary energy lowering by the segregation of these alloying elements.
Most probably that more careful analysis of electronic charge density transfer subsequent to the impurity presence is most important for a comprehensive understanding of the physics and mechanisms of this enhancement. This work, relatively more cumbersome than the energy calculations is obviously our next objective.
Accordingly, systematic and comprehensive study of the alloying impurities effect Ti and Zr on the properties of Fe3Al has been carried out using electronic Density Functional Theory. The total energy has been calculated employing ultrasoft pseudopotentials and the generalized gradient approximation. The impurity formation energies of Ti and Zr are calculated for different configurations both in the bulk material and in grain boundary in DO3 lattice.
A number of conclusions can be drawn from our calculation results. In the following are resumed the most important ones:
(i) In bulk material:
The calculated formation energies correctly predict the experimentally known behavior of Titanium, namely its preference to occupy the FeI site. Zirconium atom presents the same behavior preferring to reside in the FeI lattice site. However, formation energy of this later is greater than that found for titanium. This implies that titanium atoms form stronger bonding with iron atoms than do zirconium ones. Also, vacancies are found to occur more likely on FeII lattice site again in agreement with experiment.
(ii) In grain boundary:
Comparing the impurity formation energies of Ti and Zr at the grain boundary and bulk material, we found that Ti and Zr at grain boundary have the lowest impurity formation energies. We predict that both Ti and Zr prefer to segregate at grain boundary in DO3 -Fe3Al. From energetic point of view, Ti and Zr atoms can lower the grain boundary energy.
So the actions of Ti and Zr at grain boundary play an important cohesive role suggesting that both Ti and Zr reinforce bonds through the grain boundary. This is to be correlated with the previous statement that there exist strong interatomic interactions between Ti and its adjacent FeII atoms. On another hand, Zr-doped grain boundary, it is found that the strong interatomic interactions are between Zr and its adjacent FeI atoms.
In conclusion, our calculation results suggest that the strengthening effect of Ti and Zr in DO3 -Fe3Al originates from the grain boundary energy lowering by the segregation of these alloying elements.
Most probably that more careful analysis of electronic charge density transfer subsequent to the impurity presence is most important for a comprehensive understanding of the physics and mechanisms of this enhancement. This work, relatively more cumbersome than the energy calculations is obviously our next objective.
Date d’inscription en doctorat : Décembre 2008
Intitulé:
Description du sujet de Thèse:
Intitulé:
Description du sujet de Thèse:
Communications internationales
- Energetics of Ti and Zr transition metals in a DO3 Fe3Al S5 (310) [001] grain boundary. S. Chentouf, J-M. Raulot, H.I. Faraoun, H. Aourag and T. Grosdidier. 5th Discussion Meeting on the Development of Innovative Iron Aluminium Alloys. Prague, Czech Republic, September 21-24, 2009.
- Transition metal Zr and Ti effect on bulk and S5 (310) [001] grain boundary in DO3 Fe3Al intermetallic. S. Chentouf, H.I. Faraoun, J-M. Raulot, H. Aourag and T. Grosdidier. 5ème Congrès International en Sciences et Génie des matériaux, CISGM-5 Guelma - Algérie. 22-24 novembre 2008.
Communications nationales
- “Ab-initio energies of Ti and Zr transition metals in a DO3 Fe3Al S5 (310) [001] grain boundary”. S. Chentouf, H. Faraoun, J-M. Raulot, T. Grodidier et H. Aourag. Colloque National sur les Techniques de Modélisation et de Simulation en Science des Matériaux, Sidi Bel-abbès, 23-24 Novembre 2009 (Algérie).