The cause of '475 C embrittlement' of ferritic steel Kh25 from the standpoint of fracture... more The cause of '475 C embrittlement' of ferritic steel Kh25 from the standpoint of fracture mechanics is considered. An upward shift of the curve of the temperature-dependent local yield stress is shown to have a decisive influence on the location of the brittle-to-ductile transition temperature and its increase due to 475 C aging. The effects under consideration are connected with
Shape memory effect and intrinsic damping capacity (amplitude dependent internal friction ADIF) o... more Shape memory effect and intrinsic damping capacity (amplitude dependent internal friction ADIF) of Ti-50.6 wt.%Ni alloy have been investigated in different structural states (cold- worked, polygonizing and recrystallization, quenching). Relationship between `normal' plastic deformation due to the dislocation motion and deformation due to martensite transformation are discussed.
ABSTRACT Dynamical mechanical and positron annihilation spectroscopies were applied to study the ... more ABSTRACT Dynamical mechanical and positron annihilation spectroscopies were applied to study the structure of two Fe-Ga alloys with 18 and 21 at. pct Ga after quenching and subsequent annealing. It was found that the alloy with 18 pct Ga has much better damping capacity (psi = 30 pct) than the alloy with 21 pct Ga (psi = 5 pct). The reason for that is the ordering of the Ga atoms in Fe-21Ga alloy. Ordering processes in both alloys are studied at heating by differential scanning calorimetry, dilatometry, and internal friction or by step-by-step annealing using positron annihilation spectroscopy and hardness tests. Experimental results are explained by sequence of ordering transitions: A2 - D03 - L12.
Anelastic effects caused by carbon and vacancy diffusion in Fe3Al based alloys with and without s... more Anelastic effects caused by carbon and vacancy diffusion in Fe3Al based alloys with and without strong carbide forming elements (Ti and Nb) are investigated by internal friction measurements. The decrease of the Snoek peak in Fe–26Al–2Ti and Fe–26Al–0.3Nb alloys with respect to the Fe–26Al alloy is related to a decrease in the amount of interstitially dissolved carbon (C). The so-called X peak, which is observed in the Fe–26Al alloy, also almost disappears after alloying. In order to elucidate the vacancy contribution to the origin of the X peak radiotracer measurements of 59Fe diffusion were performed. The results indicate that the change in the interstitially dissolved C concentration is the main reason of the observed changes in the X peak, although a certain influence of Ti and Nb alloying on the total vacancy concentration may be deduced from the diffusion study.
ABSTRACT Temperature dependent internal friction (TDIF) spectra in Fe–(25–26)at.%Al alloys were s... more ABSTRACT Temperature dependent internal friction (TDIF) spectra in Fe–(25–26)at.%Al alloys were studied using different mechanical spectroscopy techniques in a wide range of vibrating frequencies from 0.1 Hz to 1 kHz. Four relaxation peaks are observed (D, S, X, Z peaks), at least two of them (D, X) have not been reported earlier in Fe3Al intermetallic compounds. The nature of these peaks is discussed. Special emphasis is put in this paper on the instability of the Fe–Al structure with respect to heating during TDIF measurements.
The cause of '475 C embrittlement' of ferritic steel Kh25 from the standpoint of fracture... more The cause of '475 C embrittlement' of ferritic steel Kh25 from the standpoint of fracture mechanics is considered. An upward shift of the curve of the temperature-dependent local yield stress is shown to have a decisive influence on the location of the brittle-to-ductile transition temperature and its increase due to 475 C aging. The effects under consideration are connected with
Shape memory effect and intrinsic damping capacity (amplitude dependent internal friction ADIF) o... more Shape memory effect and intrinsic damping capacity (amplitude dependent internal friction ADIF) of Ti-50.6 wt.%Ni alloy have been investigated in different structural states (cold- worked, polygonizing and recrystallization, quenching). Relationship between `normal' plastic deformation due to the dislocation motion and deformation due to martensite transformation are discussed.
ABSTRACT Dynamical mechanical and positron annihilation spectroscopies were applied to study the ... more ABSTRACT Dynamical mechanical and positron annihilation spectroscopies were applied to study the structure of two Fe-Ga alloys with 18 and 21 at. pct Ga after quenching and subsequent annealing. It was found that the alloy with 18 pct Ga has much better damping capacity (psi = 30 pct) than the alloy with 21 pct Ga (psi = 5 pct). The reason for that is the ordering of the Ga atoms in Fe-21Ga alloy. Ordering processes in both alloys are studied at heating by differential scanning calorimetry, dilatometry, and internal friction or by step-by-step annealing using positron annihilation spectroscopy and hardness tests. Experimental results are explained by sequence of ordering transitions: A2 - D03 - L12.
Anelastic effects caused by carbon and vacancy diffusion in Fe3Al based alloys with and without s... more Anelastic effects caused by carbon and vacancy diffusion in Fe3Al based alloys with and without strong carbide forming elements (Ti and Nb) are investigated by internal friction measurements. The decrease of the Snoek peak in Fe–26Al–2Ti and Fe–26Al–0.3Nb alloys with respect to the Fe–26Al alloy is related to a decrease in the amount of interstitially dissolved carbon (C). The so-called X peak, which is observed in the Fe–26Al alloy, also almost disappears after alloying. In order to elucidate the vacancy contribution to the origin of the X peak radiotracer measurements of 59Fe diffusion were performed. The results indicate that the change in the interstitially dissolved C concentration is the main reason of the observed changes in the X peak, although a certain influence of Ti and Nb alloying on the total vacancy concentration may be deduced from the diffusion study.
ABSTRACT Temperature dependent internal friction (TDIF) spectra in Fe–(25–26)at.%Al alloys were s... more ABSTRACT Temperature dependent internal friction (TDIF) spectra in Fe–(25–26)at.%Al alloys were studied using different mechanical spectroscopy techniques in a wide range of vibrating frequencies from 0.1 Hz to 1 kHz. Four relaxation peaks are observed (D, S, X, Z peaks), at least two of them (D, X) have not been reported earlier in Fe3Al intermetallic compounds. The nature of these peaks is discussed. Special emphasis is put in this paper on the instability of the Fe–Al structure with respect to heating during TDIF measurements.
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Papers by Igor Golovin