IFISUR   23398
INSTITUTO DE FISICA DEL SUR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Effect of a hydrogen pair on the embrittlement of a γ-Fe55Cr25Ni20 alloy
Autor/es:
C. LANZ; S. SIMONETTI
Reunión:
Congreso; 4th International Advances in Applied Physics and Materials Science Congress & Exhibition; 2014
Resumen:
During service, the introduction of atomic hydrogen into alloys causes the metal to become embrittled. Due to the engineering significance, it is important to determine the conditions under which embrittlement occurs and in quantifying the effects. The interaction of two-hydrogen atoms in a γ-Fe55Cr25Ni20 alloy was studied by the atom superposition and electron delocalization molecular orbital method. The H impurities are located aligned both along 1-10 direction and with a vacancy, in the (111) plane. This behavior can be related with a lineal hydrogen-vacancy clusterization, as a precursor to crack initiation. The electronic structure of the Fe, Cr and Ni atoms near the vacancy, changes after hydrogen?s location. The interactions mainly involve Fe 4px and Cr 4py atomic orbitals. The 3dx2-y2, 3dz2 and 3dxz metallic orbitals have also participation in the hydrogen-alloy interactions. An electron transfer to the H atoms from the Fe, Cr and Ni nearest neighbor atoms contributes to form the H-metal bonds. The metal-metal bonds weakened as the H-Fe, H-Cr, and H-Ni pairs were formed. The Cr atoms have an important role in the embrittlent process; the strengths of the Cr-Fe, Cr-Cr and Cr-Ni bonds are the most affected while the H-Cr interaction has the highest overlap population. Same H-H interaction is observed and could be associated with the precursor of hydrogen bubble but it is far away to a typical H2 chemical bond. All cited physical and chemical processes play a key role in subsequent localized corrosion nucleation such as the initiation of stress corrosion cracking.