Activation Energy Measurement of Oxygen Ordering in a Nb-Ti Alloy by Anelastic Relaxation

Abstract

Metals with bcc structure are able to dissolve large amounts of interstitial element atoms in the form of oxygen. These atoms diffuse through the lattice by jumping into octahedral sites with equivalent symmetry, causing strong alterations in the anelastic behavior. This paper reports on a study of Snoek relaxation in Nb-Ti alloys with oxygen in solid solution, based on internal friction as a function of temperature. The internal friction measurements were taken in a torsion pendulum operating at temperatures in the range of 350 to 650 K, with frequencies varying from 6 to 36 Hz. The results show relaxation spectra in which thermally activated relaxation peaks produced by the stress-induced ordering of oxygen atoms around niobium atoms of the metallic matrix were identified.

Anelastic relaxation caused by interstitial atoms in β-type sintered Ti–Nb alloys

“…[7][8][9][10][11][12]. Oxygen jumps in bcc solution are the main physical mechanism of the peak [7][8][9][10][11][12]. In Ti-Nb alloy, it is extremely difficult to remove oxygen even though the heat treatment is conducted at high vacuum.…”

Research Progress on the Point-defect Relaxation in β-Ti Alloys

“…It has been known that there must be interstitial impurity C and O atoms in the steel. Similarly, Ti alloys contain the interstitial impurity O,N atoms, which is common interstitial impurity atoms [3,[15][16]. In β-Ti alloys, O or N atoms occupying the octahedral interstitial positions can produce the anelastic relaxation under the applying of cycle stress.…”

“…The complex factors result in the complicated relaxation processes and the broadened Snoek peaks. In Nb-3.1at.%Ti alloys, the stress-induced ordering of the interstitial impurity O atoms around Nb atoms of metallic matrix (Nb-O),stress-induced ordering of oxygen atoms around Ti atoms of metallic matrix (Ti-O) and stress-induced ordering of nitrogen atoms around niobium atoms of the metallic matrix (Nb-N process) [36].Niemeyer et al [15] studied the internal friction of Nb-0.3 (wt. )% Ti, which should belong to anelastic relaxation of β-type Nb alloys.…”

Espectroscopia anelástica em ligas de Nb-16% p. Ti

“…Os resultados obtidos neste trabalho estão em discordância com os resultados apresentados na literatura [8][9][10][11] . Desta forma, podemos concluir inicialmente, que o pico em questão não é somente devido à reorientação induzida por tensão de áto-mos de oxigênio em torno de átomos de nióbio da matriz metálica.…”

“…Três processos de relaxação anelástica foram propostos: a reorientação induzida por tensão dos áto-mos de oxigênio em torno de átomos de nióbio (Nb-O); a reorientação induzida por tensão de pares de átomos de oxigênio em torno de átomos de nióbio (Nb-O-O) e a reorientação induzida por tensão de átomos de oxigênio em torno de átomos de titânio (Ti-O), descrevendo o processo de interação substitucional-intersticial. As entalpias de ativação para os três processos propostos foram fixadas, baseando-se em valores determinados por experimentos de atrito interno [9][10][11] , isto é, 1,15, 1,18 e 1,23 eV, respectivamente. As Figs.…”