The Hydrogen Influence upon Oxygen Snoek Relaxation in Nb-Ti Alloys

Golovin, I.S.; Blanter, M. S.; Vasiliev, Alexander

doi:10.1051/jp4:1996820

Cited by 3 publications

(6 citation statements)

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“…The change in activation energy for carbon diffusion in ␣ -Fe due to alloying by Al and ordering is explained using the latter case, the chemical attraction between C and Cr atoms is the main factor, but, in the case of Zener relaxation, the Khachaturyan theory of strain-induced interaction [20] and the simulation method [21][22][23][24][25][26][27][28][29] for internal-friction interpretawhere an elastic dipole is created by two neighboring atoms, the role of Cr is lower.…”

Section: E Effect Of Ordering and Ordering Kineticsmentioning

confidence: 99%

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Relaxation mechanisms in Fe-Al-C alloys

Golovin

Mukherji

Pozdova

et al. 2003

Metall Mater Trans A

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The relaxation spectrum of Fe-Al alloys has been studied as a function of Al content and ordering reaction in Fe-Al. Three types of relaxation peaks are observed, with activation energies between 0.8 and 3 eV. Snoek-type relaxation is studied in Fe-(0 to 50 at. pct)Al and compared with the Snoek relaxation in pure iron (C in ␣ -Fe), chromium (C in Cr), and niobium (O in Nb). The snoek-type relaxation peak in iron (at 314 K for 1 Hz) shifts to higher temperatures with increasing Al content in iron. Significant changes in the peak parameters occur when ␣ -Fe is alloyed with Al, because of the ordering reaction in Fe-Al. Peculiarities of the carbon-atom distribution in ordered and disordered Fe-Al alloys are discussed using an atom-interaction model, in which the elastic interaction is supplemented by the chemical C-Al interaction. Two other peaks are observed only when a certain Al content is exceeded: a Zener peak for Fe-(Ͼ10 pct)Al and an X peak for Fe-(Ͼ26 pct)Al. Parameters of these peaks are discussed with respect to alloy structure. Three hypotheses are discussed for the X-peak mechanism with an activation energy about 1.7 eV. A map of relaxation peaks in the Fe-Al system is constructed.

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Section: E Effect Of Ordering and Ordering Kineticsmentioning

confidence: 99%

“…This has been applied for an internal-friction applicaquestion of peak stability during measurement. In addition, the experimental results of this article are compared with tion in different bcc [9,[25][26][27] and fcc [22,28,29] alloys by Blanter and Golovin. Coupling effects from C-C atom interaction, available data from the literature.…”

Section: Introductionmentioning

confidence: 98%

Relaxation mechanisms in Fe-Al-C alloys

Golovin

Mukherji

Pozdova

et al. 2003

Metall Mater Trans A

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“…From one hand it takes only about 0.3 . s. to create the above mentioned hydrogen atmospheres at dislocations [4]. From the other hand the sharp yield point is observed on stress-strain compression test curves of hydrogenized Nb-Ti samples.…”

Section: Introductionmentioning

confidence: 79%

The Study of Microplasticity Mechanism in Ti-50 wt.%Nb Alloy with High Hydrogen Content

1996

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Abstract. The upper yield point ( = 700 MPa ) appears at the compression test curves (~0 . 0 2 4 sw-1) of b.c.c.Nb-50wt.%Ti due to the increase of hydrogen content from 0 to 0.2 wt.% and more and leads to the non monotonous increase in compressive lower yield stress from 400 to 550 MPa. Taking into account close connection between macro-and microplasticity of metallic materials the low frequency (-2 Hz) amphtude dependent internal friction (ADIF) spectrum (y = 1 .. 60.10-5) in hydrogenized Nb-50 wt.% Ti and Nb samples are studied. The ADIF investigation of the closed hysteresis loop "loading-unloading" shows the dependence of its width from the hydrogen content which evidences the fact of dislocation unpinning from hydrogen atmospheres in the 112 cycle of loading. The study of ADIF spectrum for samples with different hydrogen content before and after torsion deformation (y = 2%) shows the sharp increase of IF level at y = 1 .. 10 after =I hour of natural ageing. At that time the ADIF curves change its shape from r-shape to U-shape. The amplitude range of the IF increase depends on the hydrogen content. It is the interaction of hydrogen atoms with dislocations that caused the above mentioned effect which has not been observed in hydrogen free samples. The time estimation for the formation of thermodynamically stable hydrogen atmospheres on dislocations shows that hydrogen atmospheres could not follow the dislocation during compressive tests and that leads to the upper yield point appearance.

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“…The other situation with influence of more mobile interstitial atoms on diffusion under the stress of 'heavy' interstitial atoms is not enough studied. In particular, this case takes place with the hydrogen influence on oxygen Snoek relaxation in Nb [4,5]. Figure 4 illustrates the influence of hydrogen on oxygen Snoek relaxation in Nb.…”

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confidence: 93%

“…,K 50 [47] 79 [48,49] 106 [31,49] 77 [48] 60 [9] 50 [8] 126 [7] The Hydrogen Influence Upon Oxygen Snoek Relaxation in Nb [5] In the previous example we discussed the situation when practically immobile 'heavy' interstitial atoms (O, N) influence on Snoek-type hydrogen relaxation in Nb and Ta. In this case the mechanical relaxation spectra could be explained from the viewpoint of (O,N)-(H,D) interatomic pair interactions.…”

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Hydrogen Interaction with Dissolved Atoms and Relaxation Properties of Metal Solid Solutions

Blanter

Magalas²

2006

SSP

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The H(D) atom’s interaction with one another, ‘heavy’ interstitial atoms (O, N, C), and substitutional atoms is analyzed on the basis of strain-induced (elastic) interaction. The interaction energies are calculated for bcc, fcc, and hcp metal solid solutions with regard to the discrete atomic structure of the host lattice. The elastic constants, Born-von Karman constants of the host lattice, and concentration expansion coefficients of the solid solution lattice due to solute atoms, are used as the parameters for numerical input. It is shown that the interaction is long-range, oscillating, and anisotropic. In all cases, the coordination shells of both types - with attraction and with repulsion - exist. The interaction energy dependence on the distance is due mainly to the crystal lattice type. The strain-induced interaction should be supplemented by repulsion in the nearest coordination shells for the case of interstitial-interstitial interaction and by chemical interaction in the case of H-substitutional interaction. Two examples are given for the use of the strain-induced interaction energies in calculations relaxation processes.

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The Hydrogen Influence upon Oxygen Snoek Relaxation in Nb-Ti Alloys

Cited by 3 publications

References 5 publications

Relaxation mechanisms in Fe-Al-C alloys

Relaxation mechanisms in Fe-Al-C alloys

The Study of Microplasticity Mechanism in Ti-50 wt.%Nb Alloy with High Hydrogen Content

Hydrogen Interaction with Dissolved Atoms and Relaxation Properties of Metal Solid Solutions

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