High Temperature Internal Friction Research Articles

Effect of Sc contents on the mechanical properties and damping capacity of Al–Zn–Mg–Cu–Zr–Sc alloys with different grain structures

Al–Zn–Mg–Cu–Zr–Sc alloys with different Sc contents were fabricated by casting, deformation, and T6 treatment. Deformation methods including rolling and friction-stir processing (FSP) were used to design their grain structure. A low additive amount (0.1) of Sc cannot refine the grains of the alloy with rolling and T6 treatment, and it instead coarsened the grains. The reason was the non-uniform distribution of nanosize Al3(Sc,Zr) phases that led to the occurrence of abnormal grain growth during homogenization. Meanwhile, the alloy with only 0.1Sc exhibited finer grains after FSP and T6 treatment than the alloys subjected to the same process but with higher Sc additive amount. Alloys with rolling-induced elongated grain structure exhibited better mechanical properties, and alloys with FSP-induced fine equiaxed grain structure exhibited higher high-strain and high-temperature internal friction values. These features are important performance parameters for applications in fields where vibration and noise are sensitive. The optimum additive amounts of Sc for alloys with elongated and fine equiaxed grain structures were 0.25 and 0.1, respectively.

Internal friction in thin-film ferrite bismuth with an amorphous structure

The internal friction spectra of an amorphous thin-film bismuth ferrite deposited on a silicon substrate were studied. The temperature dependence of mechanical losses near the glass transition temperature revealed a wide maximum of internal friction associated with α-relaxation of the amorphous structure. In this temperature region, two linear sections in the ln Q −1 vs (1/ T ) dependence are observed with an intersection point at the glass transition temperature. According to the results of low- and high-temperature internal friction investigation of the amorphous bismuth ferrite in the α-relaxation region, the values of the migration energy and the formation energy of vacancies-like defects were estimated, which are equal to E m = 0.80 ± 0.08 eV and E v = 0.88 ± 0.08 eV, respectively. • Internal friction Q −1 in amorphous bismuth ferrite BiFeO 3 at high temperatures was studied. • The Q −1 maximum is due to α-relaxation of the amorphous structure in thin-film BiFeO 3 . • Crystallization of the amorphous structure of BiFeO 3 is confirmed by the results of DTA and X-ray diffraction analysis. • Estimates of the migration energy and the formation energy of oxygen vacancies in the amorphous BiFeO 3 were made.

On the vacancy nature of the high-temperature background of internal friction in solids

High-temperature internal friction in an amorphous CuTi alloy is investigated. Exponential regions with different activation energies are observed on the dependence of internal friction on temperature on both sides of the glass transition temperature. An exponential increase in the background of internal friction with temperature in both sites is associated with the migration of vacancy-like defects in the amorphous structure under the influence of mechanical stresses, while frozen defects of constant concentration migrate to the glass transition temperature. After the transition to a state of thermodynamic equilibrium, the concentration the number of migrating defects increases exponentially. Based on the experimental results of measuring the high-temperature background, estimates of the activation energy of migration and the formation of vacancies of similar defects in the amorphous structure of the alloy under study are made. Keywords: Internal friction, relaxation time, high temperature background, amorphous alloy.

О вакансионной природе высокотемпературного фона внутреннего трения в твердых телах

High-temperature internal friction in an amorphous CuTi alloy is investigated. Exponential regions with different activation energies are observed on the dependence of internal friction on temperature on both sides of the glass transition temperature. An exponential increase in the background of internal friction with temperature in both sites is associated with the migration of vacancy-like defects in the amorphous structure under the influence of mechanical stresses, while frozen defects of constant concentration migrate to the glass transition temperature. After the transition to a state of thermodynamic equilibrium , the concentration the number of migrating defects increases exponentially. Based on the experimental results of measuring the high-temperature background, estimates of the activation energy of migration and the formation of vacancies of similar defects in the amorphous structure of the alloy under study are made.

Активационные характеристики вязкоупругих свойств жаропрочного сплава на основе системы Ni-Co-Cr, упрочненного объемным азотированием

The results of measurements of the high-temperature internal friction background of the heat-resistant alloy VZh171 in the initial state and after volume nitriding presented. The obtained data used to study the regularities of the transition from the elastic to the viscoelastic state of the material at elevated temperatures. Nitriding the alloy leads to an increase in the transition temperature to the viscoelastic state from 571 K (initial state) to 763 K (after nitriding). The values of activation energy of the high-temperature internal friction background obtained: U f = 0.63 ± 0.01 eV for the alloy VZh171 in the initial state and U f = 0.59 ± 0.01 eV for the alloy after volume nitriding. The activation energies U 0 of the processes responsible for the formation of the viscoelastic properties of the substance are estimated: U 0 ≈ 2.52 eV for the alloy in the initial state, U 0 ≈ 2.36 eV for the nitrided alloy. The obtained values U 0 correspond to the self-diffusion activation energy in nickel, the main component of the alloy matrix. The appearance of dispersed nitride phases in the matrix leads to a decrease in the activation energy of viscoelasticity processes by about 6%. Possible reasons for the change in the transition temperature and the activation energy of the viscoelastic state at moderately high temperatures as a result of nitriding discussed.

High-temperature phenomena in an advanced intermetallic nano-lamellar γ-TiAl-based alloy. Part I: Internal friction and atomic relaxation processes

Intermetallic γ-TiAl based alloys have found applications in the low-pressure turbine of aircraft engines as well as in the turbocharger unit of automotive engines. However, these light-weight alloys must still be improved, through micro-alloying and tailoring the microstructure, to increase their creep resistance and consequently their maximum working temperature. In this work, a fully nano-lamellar advanced γ-TiAl based alloy doped with small amounts of C and Si is investigated in order to gain a deeper understanding of the atomic mobility mechanisms taking place at high temperature, thus controlling the creep properties. The study was approached through internal friction measurements up to 1223 K. We demonstrate that C has a notable influence on Ti diffusion in α2 phase, leading to an increase of the activation energy for Ti diffusion, which is assessed at ΔETi(α2)=0.32 eV per at% C. An atomic model for the relaxation process is proposed capable to explain this phenomenon. An additional internal friction peak, which, up to now, remained hidden by the high temperature background, was observed in this nano-lamellar TiAl alloy and analyzed through a careful de-convolution of the internal friction spectra. This new relaxation process, with activation energy of 3.70 eV, is attributed to the short distance diffusion of Al atoms in the γ-TiAl lattice. A novel concept of stress-induced cell-lattice reorientation is proposed to explain this relaxation. Finally, a new experimental method to analyze the high temperature internal friction background, which is closely related to the creep behavior, was developed to study the fully nano-lamellar microstructure, whose high temperature background exhibits the highest activation energy ever measured in a γ-TiAl based alloy.

An ultrasonic study of relaxation processes in pure and mechanically alloyed tungsten

High-temperature internal friction in a pure tungsten single crystal, polycrystals with different grain sizes, and mechanically alloyed tungsten polycrystals was studied. Positron annihilation spectroscopy was used to prove that all studied materials contain a detectable amount of dislocations. Then, resonant ultrasound spectroscopy was applied to determine the internal friction evolution with temperature from room temperature up to 740 °C. For the pure tungsten samples, a sharp increase of internal friction was observed for temperatures above 470 °C (for the single crystal) or above 400 °C (for the polycrystals); the activation energy corresponding to this increase was the same as the activation energy for the ductile-to-brittle transition in tungsten reported in the literature. For the alloyed materials, direct observation of the onset of this relaxation mechanism was impossible due to additional effects resulting from the secondary phases in the material.

Effect of Sc addition on the microstructure, mechanical properties, and damping capacity of Al–20Zn alloy

In this study, hot rolling (HR), solid solution treatment (ST), and friction stir processing (FSP) were applied to Al–20Zn and Al–20Zn–0.5Sc alloys to obtain their elongated, coarsened, and fine-equiaxed grain structures. Sc addition refined the grains of Al–20Zn alloys in any state. The dynamic precipitation during deformation, such as HR and FSP, was promoted by the Al3Sc phase in the alloy containing Sc. The strength of Al–20Zn alloy was improved by Sc addition. Furthermore, a reasonable ductility was obtained in the ST sample when added with Sc. The fine grains and high density of Al3Sc particles with grain boundary pinning effect resulted in increased high-temperature internal friction value and excellent damping stability of the HR and FSP Al–20Zn–0.5Sc samples.

High temperature internal friction in Ni50.3Ti29.7Zr20 shape memory alloy

The internal friction at temperature up to 980 K in Ni50.3Ti29.7Zr20 (at.%) high temperature shape memory alloy was investigated. A relaxation peak was observed at about 750 K for 0.1 Hz. Its activation parameters were determined, Hact = 1.82 ± 0.04 eV, τ0 = 2.22 × 10−12 s. Similar relaxation peak with the activation enthalpy of about Hact = 1.42 eV was observed in NiTi binary alloy at a slightly lower temperature. Alloying of Zr is found to increase the activation enthalpy of this relaxation. The mechanism of this relaxation was discussed based on a Zener relaxation related to the short-range diffusion of Ni.

Effect of Sc addition, friction stir processing, and T6 treatment on the damping and mechanical properties of 7055 Al alloy

Sc addition, friction stir processing (FSP), and subsequent solid-solution treatment and aging to peak hardness (T6 treatment) were applied on a 7055 Al alloy. Fine equiaxed grains were obtained after FSP, and the size of the grains was further refined by minor Sc addition. Subsequent solid-solution treatment led to the dissolution of η phase, and aging led to the precipitation of η′ phase in the FSP samples. The Al3(Sc,Zr) particles effectively inhibited the grain coarsening in the Sc-containing FSP sample during the T6 process. Thus, a high density of η′ phase and a fine equiaxed grain structure were obtained in the Sc-containing 7055 alloy after FSP and T6 treatment. The special structure endowed this alloy with higher yield strength than the T6 treated 7055 alloy. FSP enhanced the high-temperature internal friction value of the Sc-containing 7055 alloy, and subsequent T6 treatment did not significantly reduce the value. The Sc-containing 7055 alloy exhibited greater high-temperature internal friction value than the T6 samples and the 7055 alloy fabricated using the same processing route.

High Temperature Internal Friction Relaxations in Cold-Rolled Titanium

The high temperature relaxation in cold-rolled Ti (CR-Ti) and commercial pure Ti (CP-Ti) has been investigated using internal friction apparatus operating in forced oscillations from room temperature to 650°C. It is shown that there is an internal friction peak at around 510°C for the CR-Ti and there is no 510°C internal friction peak in the CP-Ti. The internal friction peak shows typical features of phase transformation in the CR-Ti. It is tentatively suggested that this peak is due to the ordering of disordered lattices resulted from cold-rolling. The high temperature background damping (HTBD) in the CP-Ti is much lower than that in the CR-Ti. It is concluded that the HTBD is related to the microstructure observed inside the grains and does not dependent on grain size.

High-temperature internal friction and dynamic moduli in copper

New measurements of dynamic shear and Young's moduli and their associated internal frictions were made with torsional and flexural forced-oscillation methods, respectively, on three polycrystalline specimens of pure copper. The tests spanned the 1–1000 s range of oscillation periods, at temperatures ranging from those of annealing close to the melting point (1050 °C) down to room temperature. A broad internal friction peak, found at temperatures around 700 °C (at 1 Hz) for samples annealed at 1050 °C, is superimposed on a monotonic relaxation background. Non-linear viscoelastic behaviour is observed above strains around 5×10−6. The period- and temperature-dependence of both shear modulus and internal friction is adequately captured by an extended “background plus peak” Burgers model for viscoelastic rheology. Activation energies are found to be around 200 kJ mol−1 for both the high-temperature peak and monotonic damping background, consistent with common diffusional control of both the dissipation background and superimposed peak, plausibly involving stress-induced migration of dislocations. Complementary torsional microcreep tests at selected temperatures reveal that most of the inelastic strain is anelastic (viscous) for loading durations less (greater) than 1000 s. Such linear viscous deformation, observed at low stress in coarse-grained polycrystalline copper, involves much higher strain rates than expected from published rheology, plausibly attributable to the Harper-Dorn mechanism.

High temperature internal friction in a Ti–46Al–1Mo–0.2Si intermetallic, comparison with creep behaviour

Advanced γ-TiAl based intermetallics Mo-bearing have been developed to obtain the fine-grained microstructure required for superplastic deformation to be used during further processing. In the present work we have studied an alloy of Ti–46.8Al–1Mo–0.2Si (at%) with two different microstructures, as-cast material with a coarse grain size above 300 μm, and the hot extruded material exhibiting a grain size smaller than 20 μm. We have used a mechanical spectrometer especially developed for high temperature internal friction measurements to study the defect mobility processes taking place at high temperature. The internal friction spectra at different frequencies has been studied and analyzed up to 1360 K in order to characterize the relaxation processes appearing in this temperature range. A relaxation peak, with a maximum in between 900 K and 1080 K, depending on the oscillating frequency, has been attributed to Ti-atoms diffusion by the stress-induced reorientation of Al–VTi–Al elastic dipoles. The high temperature background in both microstructural states, as-cast and extruded, has been analyzed, measuring the apparent activation parameters, in particular the apparent energies of Ecast(IF) = 4.4 ± 0.05 eV and Eext(IF) = 4.75 ± 0.05 eV respectively. These results have been compared to those obtained on the same materials by creep deformation. We may conclude that the activation parameters obtained by internal friction analysis, are consistent with the ones measured by creep. Furthermore, the analysis of the high temperature background allows establish the difference on creep resistance for both microstructural states.

Mechanical Spectroscopy Of Equal-Channel Angular Pressed Fe-Cr Alloys And Tungsten

Abstract Internal friction technique was used to investigate the microstructural stability of equal-channel angular pressed (ECAP) 9Cr1Mo steel (T91), Fe-18wt.%Cr alloy, and pure W. Several non-relaxation internal friction peaks are observed in three ECAP-strained specimens, which are related to the microstructural transition from a severely deformed state to a static recovery state of dislocations, and to recrystallized state. Along with the disappearance of the P1 peak, another relaxation internal friction peak P2 is observed during the second heating run only in Fe-18wt.%Cr alloy, and it does not disappear even during subsequent third heating run. This peak is not observed in T91 steel and W. The P2 peak is likely associated with a process of grain boundary (GB) sliding. Unlike T91, no abundant carbide precipitates distribute on GBs to pin GB and repulse GB sliding, thus, the P2 peak only occurs in Fe-18wt.%Cr alloy. It is concluded that high-temperature internal friction measurements are required to detect the grain boundary peak in pure W.

High temperature internal friction measurements of 3YTZP zirconia polycrystals. High temperature background and creep

Abstract This work focuses on the high-temperature mechanic properties of a 3 mol% yttria zirconia polycrystals (3YTZP), fabricated by hot-pressureless sintering. Systematic measurements of mechanical loss as a function of temperature and frequency were performed. An analytical method, based on the generalized Maxwell rheological model, has been used to analyze the high temperature internal friction background (HTB). This method has been previously applied to intermetallic compounds but never to ceramics, except in a preliminary study performed on fine grain and nano-crystalline zirconia. The HTB increases exponentially and its analysis provides an apparent activation enthalpy which correlates well with that obtained from creep experiments. This fact shows on the one hand the plausibility of applying the generalized Maxwell model to ceramics, and on the other hand indicates the possibility of using mechanical spectroscopy as a complementary helpful technique to investigate the high temperature deformation mechanism of materials.

A Study on Influence of Annealing and Aging on High Temperature Internal Friction in Al-Zr Alloy

By using a low frequency inverted torsion pendulum, the high temperature internal friction spectra of Al-0.02wt%Zr and Al-0.1wt%Zr alloys were investigated respectively. In Al-0.02wt%Zr alloy, the conventional grain boundary internal friction peak (Pg) is observed with some small unstable peaks. In Al-0.1wt%Zr alloy, the bamboo peak is observed to appear at the high temperature side of the conventional grain boundary internal friction peak. The conventional grain boundary internal friction peak decreased and moved to higher temperature. The bamboo peak owns an activation energy of 1.75eV. When average grain size exceeded the diameter of samples, Pb strength was reduced and its position was shifted to a lower temperature. Based on the grain boundary sliding model, Pg and Pb peaks were explained. Their dependence on annealing temperature and time was determined by considering the effects of contained Ce atoms and other impurities on the relaxation across grain boundary.

High Temperature Internal Friction in Fine Grain and Nano-Crystalline Zirconia

Engineering ceramics are being developed to improve their high-temperature mechanical properties and in particular creep resistance. Recently the production of fine grain ceramics undergoes another step-forward with the development of new technologies to produce nanocrystalline materials. The question is whether the properties depending on the grain size can be extrapolated at nanoscale or, on the contrary, new microscopic mechanisms could appear to be dominant at this nanometer grain size. In the present work we study, by mechanical spectroscopy, the high temperature behavior up to 1350°C of a fine grain Zirconia and a nanocrystalline Zirconia sintered in a conventional way. A new forced torsion pendulum, recently built, has been used for the mechanical spectroscopy measurements. The high temperature background (HTB) of internal friction has been measured as a function of temperature for different frequencies in both materials. The analysis of the HTB shows that the fine grain Zirconia exhibits a single process of defects mobility, with an apparent activation enthalpy similar to the one measured by creep. On the contrary, the HTB of the nanocrystalline sample becomes more complex, showing a much higher energy loss, which will be discussed at the light of the internal friction spectra analysis.

Influences of Annealing and Deformation on the High Temperature Internal Friction Spectra of Al-0.013%Wt Ce Alloy

By using a low frequency inverted torsion pendulum, the high temperature internal friction spectra of Al-0.013wt%Ce alloy subjected to deformation at different tensile rates was measured, and three peaks, the conventional grain boundary peak (P1), the bamboo peak (P2) and the soild solution peak (P3) were found. Increases of annealing temperature and deformation rate make P1 and P2 lower with P1 shifting to higher temperature and P2 to lower temperature. P3 was only found in the as-received samples. The dependence of P1 and P2 on grain size indicates that the two peaks are originated from the grain boundary sliding, and P3 may be associated with the diffusion of Ce atoms or other impurities at grain boundaries.

Glass and crystallization like transitions at low temperature in Zr-Cu based glasses by internal friction measurements

Low temperature β internal friction peak evolution upon thermal cycles shows two peculiar peaks similar to high temperature internal friction peak. The modulus softening associated to these peaks suggest a phase transformation phenomenon and the relaxation time τo in order of 10 -23 -10 -35 s, close to that observed in grains boundary sliding are due to interface motions in the amorphous structure under combined thermal and mechanical energies.

Temperature dependence of the internal friction of polycrystalline indium

The temperature dependences of the internal friction and the elastic modulus of polycrystalline indium have been investigated in the temperature range 7–320 K at oscillatory loading frequencies of approximately 100 kHz. The effect of temperature on the amplitude dependence and the effect of high-amplitude loading at 7 K on the temperature and amplitude dependences of the internal friction of indium have been analyzed. It has been demonstrated that the thermocycling leads to microplastic deformation of indium due to the anisotropy of thermal expansion and the appearance of a “recrystallization” maximum in the spectrum of the amplitude-dependent internal friction. The conclusion has been drawn that the bulk diffusion of vacancies and impurities begins at temperatures of approximately 90 K and that, at lower temperatures, the diffusion occurs in the vicinity of dislocations. It has been revealed that the high-temperature internal friction background becomes noticeable after the dissolution of Cottrell atmospheres.