Banca de QUALIFICAÇÃO: JAMES BERGAMASCO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : JAMES BERGAMASCO
DATE: 11/11/2022
TIME: 14:00
LOCAL: Bloco B, Santo André
TITLE:

Effect of Niobium on the motion of dislocations in fire resistant steels: a computational approach

PAGES: 94
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Propriedades Físicas dos Metais e Ligas
SUMMARY:

After the attack on the Twin Towers on September 11, 2001, Fire Resistant (RF) steels have gained significant increase in demand in the construction industry, being a recognized material of great importance to the preservation of life. Accidents involving fires are common throughout the world and responsible for many lives lost due to catastrophic collapses caused by the reduced mechanical strength of structural steel subjected to heat. Numerous researches have been conducted to prevent a drop to dangerous levels of the yield strength of steel in case of fire accidents, and the literature shows that the most advantageous way is the addition of alloying elements, especially the transition metal niobium (Nb). Brazil currently holds 95% of the world's Nb reserves, making it the leader in the production of Fe-Nb alloys (average of 50 thousand tons per year), absorbing 80% of the world market. A deep understanding is needed to develop such alloys that meet the application needs. The movement of dislocations is the main phenomenon causing the plastic deformation of metals, the mobility of dislocations at high temperatures cause interaction between them and lower their density, reducing the value of the yield strength mechanical property of steel. This work investigates, through simulations of classical Molecular Dynamics (MD), the effect of the niobium alloying element as a barrier to the movement of dislocations at high temperatures. The mobility of a screw dislocation in four different systems was studied for room temperature (300 K) and for critical temperature reached in fires (900 K). Simulation results at 900K reveal that the substitutional atom of the Nb alloying element, having as its crystal lattice neighbor a vacancy, produces expressively higher Peierls barrier energy levels than the Nb alloying element having as its neighbor the Fe atom. This makes the use of Nb favorable compared to other substitutional alloying elements such as Mo, Cr, Ni, Mn, since the energy required for the formation of vacancy offered by the Nb substitutional atom is the lowest. Furthermore, the simulations show that the value of the critical shear stress for the dislocation slip with only one Nb-vacancy pair at the temperature of 900K in its path was almost 5 times higher compared to a system without alloying elements. The benchmarks obtained from the MD simulations lead to a better science of the effects of the Nb alloying element for FR steel fabrication, directing experimental studies and future works.

BANKING MEMBERS:
Presidente - Interno ao Programa - 1925199 - ANIBAL DE ANDRADE MENDES FILHO
Membro Titular - Examinador(a) Interno ao Programa - 1893637 - ALEJANDRO ANDRES ZUNIGA PAEZ
Membro Titular - Examinador(a) Externo ao Programa - 1957564 - CEDRIC ROCHA LEAO
Membro Suplente - Examinador(a) Interno ao Programa - 1765425 - MARCIO GUSTAVO DI VERNIERI CUPPARI
Membro Suplente - Examinador(a) Externo ao Programa - 1309493 - PEDRO ALVES DA SILVA AUTRETO