Temperature Dependence Of Internal Friction Research Articles

Internal friction study of dislocation dynamics in neutron irradiated iron, and iron–copper alloys

The temperature dependent internal friction spectra of cold-worked and neutron irradiated iron and iron–copper binary alloys are investigated. By increasing dose, both γ - and Snoek-Köster-relaxation peaks exhibit strong shift towards low temperatures, as a consequence of the reduction of double kink activation energy. This shift is found to be the largest in alloys with the highest copper content. Besides, new modes appear in the spectra at energies of about 410 and 540 K. The 410 K peak intensity increases at the expense of Snoek-Köster peak intensity, indicating that redistribution of carbon takes place under irradiation, most probably as a result of grain boundary segregation. The presence of copper impedes the carbon redistribution by influencing the formation of carbon-vacancy complexes, which causes the grain boundary segregation, and activation of the 410 K relaxation process at larger neutron fluence in comparison with pure iron.

A new viewpoint to the mechanism for the effects of melt overheating on solidification of Pb-Bi alloys

The effects of melt overheating treatment on solidification of Pb-Bi alloys were studied from the viewpoint of liquid-liquid structure change (LLSC). Anomalous temperature dependence of internal friction, electrical resistivity, and entropy of liquid Pb-Bi alloys suggested that discontinuous LLSC occurred within about 520–740 °C, based on which the solidification experiments were carried out with different states of Pb-Bi melts. The results revealed that the LLSC affected the solidification behavior and microstructures significantly, that is, the enlarged undercooling, increased nucleation rate, and refined and improved morphologies were brought about when solidifying from the melt experienced LLSC. It is assumed that the LLSC changed the energy constitution of the melt system, and further affected the effective partition coefficient, thermodynamics, and kinetics of crystal growth, then finally altered the solidification behavior and solidified microstructures. This work brings a novel insight into the effect of melt overheating treatment on solidification, by which it could be more effective to manipulate melts.

High-temperature internal friction, stiffness and strength of Zr–Al(Si)–C ceramics

The temperature dependence of internal friction, stiffness and strength of Zr-Al(Si)-C ceramics was studied. For glass-free Zr-Al(Si)-C ceramics, the internal friction curve followed an exponential-like background. For liquid-phase-sintered Zr(3)Al(3)C(5), an internal peak present at 1590 K revealed the grain-boundary sliding due to wetting of glass phase at grain boundaries and triple junctions. Zr-Al(Si)-C ceramics exhibited high degrees of stiffness and strength at high temperatures up to 1600 and 1400 degrees C, respectively, which render them good high-temperature structural materials. (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Mechanical spectroscopy study of thermo-mechanically treated 51CrV4 steel

The CrV-alloyed heat-treatable steel (51CrV4) used for shafts is studied with respect to the influence of different heat treatment and deformation regimes on amplitude (strain amplitude 10 −6–10 −3) and temperature dependent (293–800 K; 1–600 Hz) damping. Specimens with different metallographic constituents were measured with and without magnetic field to distinguish between dislocation and magnetoelastic damping. Coercivity of all samples as well as microhardness increases in the order: ferrite–pearlite, as received, bainite and martensite. A clear difference in temperature and amplitude dependent internal friction was detected, too. A Snoek-Köster peak was found to be highest in martensitic state correlating with the dislocation density and reversible relaxation strength. Reversible stress relaxation measurements performed at room temperature from 3 s to 1 h and at a strain of 2 × 10 −5 led to a reversible relaxation strength of 0.001 for all mentioned metallographic constituents except the martensitic one which was observed to be about four times higher.

Al2TiO5-MgTi2O5セラミックス－高分子複合制振材料における内部摩擦の温度依存性

Al2TiO5-MgTi2O5セラミックス－高分子複合制振材料における内部摩擦の温度依存性

A sodium ordering transition above room temperature in Na xCoO 2 deduced by mechanical spectrum

The mechanical spectrum of Na 0.66CoO 2 above room temperature was measurement using the vibrating reed method at kilohertz frequency. A novel transition was observed around 427 K as indicated by temperature-dependent internal friction and resonance frequency. The characteristic transition temperature is defined as the start of a step increase of resonance frequency with the decrease of temperature, which is concurrent with the decrease of internal friction below a plateau. At the same time, this characteristic transition temperature shifts towards lower temperatures at a lower cooling rate, or higher heating rate during its respective thermodynamic processes. This unconventional behavior seems to be explained by critical slowing down at a second-order phase transition. Furthermore, sodium ordering is expected for this phase transition.

Effect of pulse electron beam characteristics on internal friction and structural alterations in epoxy

Temperature dependence of internal friction is experimentally studied in epoxy irradiated by 2.5 MeV pulse electron beam to different doses. Time dependence of internal friction characteristics associated with radiation-induced processes of polymer scission and cross-linking is analyzed and discussed. Experimental data on kinetics of structural transformations in epoxy are interpreted on the base of analytical solutions of differential equations for free radical accumulation during and after irradiation subject to the pulse irradiation mode and an arbitrary effective order of radical recombination.

Dose rate effect on internal friction and structural transformations in electron-irradiated carbon-armored composites

Temperature dependence of internal friction and specific electric resistance of multi-layer carbon-armored epoxy-based composites is experimentally studied in the temperature range of 20–300 °C before and after irradiation with 2 MeV electrons. It is shown that carbon penetration into the polymer matrix causes intense polymer cross-linking in the basic layers of the composite even at low irradiation doses. The strong effect of dose rate on radiation-induced structural transformations was observed.

Laser fluence dependence of the elastic properties of diamond-like carbon films prepared by pulsed-laser deposition

We studied the temperature dependence of internal friction of variety of amorphous diamond-like carbon films prepared by pulsed-laser deposition. Like the most of amorphous solids, the internal friction below 10 K exhibits a temperature independent plateau, which is caused by the atomic tunnelling states—a measure of structure disorder. In this work, we have varied the concentration of sp 3 versus sp 2 carbon atoms by increasing laser fluence from 1.5 to 30 J/cm 2. Our results show that the internal friction has a nonmonotonic dependence on sp 3 / sp 2 ratio with the values of the internal friction plateaus varying between 6 × 1 0 − 5 and 1.1 × 1 0 − 4 . We explain our findings as a result of a possible competition between the increase of atomic bonding and the increase of internal strain in the films, both of which are important in determining the tunneling states in amorphous solids. The importance of the internal strain in diamond-like carbon films is consistent with our previous study on laser fluence, doping, and annealing, which we will review as well. In contrast, no significant dependence of laser fluence is found in shear moduli of the films, which vary between 220 and 250 GPa.

The neutron structural analysis in studies of diffusionless phase transitions in shape memory alloys

The characteristics of alloys with the shape memory effect are presented. The physical nature of the process of a change in the shape is examined. The structure of the high-manganese alloys of Mn-Cu system with shape memory is described. The role of neutron analysis in studies of structural transformations in Mn-Cu alloys is shown. On the basis of the results of measuring the temperature dependences of internal friction in the magnetic fields of different magnetizing force, the presence of the magnetic contribution to the pretransition anomalies in Mn-Cu alloys is assumed. The prospects of applying the neutron analysis in studies of alloys with the shape memory generally and, in particularly, in the Mn-Cu alloys are shown.

Effect of alloying α-Fe with aluminum, silicon, cobalt, and germanium on the snoek relaxation parameters

Parameters of Snoek relaxation in binary alloys of iron with Co, Ge, Al, and Si have been studied. The concentration of Al was varied from 1.5 to 16 at. %, and that of Si, from 3 to 10 at. %, in binary (Fe-Al, Fe-Si) and ternary (Fe-Al-Si) alloys. It has been shown that Co and Ge added to α-Fe in amounts to ∼3 at. % only wekaly affect the parameters of the Snoek peak, i.e., the height, width, and shape of the peak, as well as the activation energy for diffusion of carbon atoms. Aluminum and silicon lead to a qualitatively the same effect—a broadening of the Snoek peak on the high-temperature side, which indicates an increase in the activation energy for carbon diffusion and carbon redistribution in iron. The quantitative effects of Al and Si are different. To analyze these effects, a computer analysis of the curves of the temperature dependence of internal friction has been applied.

Internal friction and brittle-ductile transition in structural materials

The temperature dependences of internal friction (ultrasound decrement) and impact toughness of bcc metals (Fe-12Cr-W-V-Ta-B-C ferritic/martensitic steel, V-4Ti-4Cr vanadium-based alloy) have been studied in a temperature range from 100 to 300 K. The acoustic and mechanical characteristics exhibit correlated variation. The use of nondestructive acoustic techniques for the investigation of mechanisms of the brittle-ductile transition in metallic structural materials is experimentally justified.

Internal friction behavior of the reverse martensitic transformation in deformed Mn [sbnd]Cu alloy

In order to study the reverse transformation dynamics of Mn Cu alloys with deformed martensitic phase, the temperature dependence of internal friction (IF) is measured under various heating rates and vibration frequencies, while the deformed martensite microstructure of the alloy is observed with scanning electron microscopy and electron backscatter diffraction at room temperature. It is found that variant reorientation of twinning martensite is induced by the applied tensile stress through detwinning and diminishing of unfavorable orientation. Meanwhile, the IF peak occurring during the reverse transformation shows different nonlinear relationships to heating rate and vibration frequency, when the martensite microstructure is deformed to different plastic strains. The coefficient n and l describing the transformation dynamics are determined from the heating rate and frequency dependent IF peaks, and the variation as well as the physical meaning of the coefficients corresponding to the changes in martensite microstructure are discussed.

Analysis of Internal Friction on Silicon Nitride with Visco-Elastic Model

Temperature dependence of internal friction on silicon nitride ceramics with yttria and alumina sintering aids was discussed using 4-elements visco-elastic model. It is known that the internal friction of this ceramic material shows a characteristic peak at around 1040 oC and an exponential increase over 1200 oC. This temperature dependence of internal friction was well approximated with using parallel Maxwell model. The parameters for this model and the relaxation time on this model were obtained. The relaxation time was very short, compared to the transient creep deformation of this ceramics. The analyzed results on internal friction could not be related with the creep deformation.

Modulus softening during the γ → ɛ martensitic transformation in Fe–25Mn–6Si–5Cr–0.14N alloys

The temperature dependences of internal friction and modulus were measured for the Fe–25Mn–6Si–5Cr–0.14N (wt.%) shape memory alloys. Compared with other Fe–Mi–Si based alloys without nitrogen, a modulus softening of the parent γ phase was observed during the γ → ɛ martensitic transformation, although the rather strong softening has been always recognized to occur during the reverse ɛ → γ transformation, due to the enhanced strength and the increased stacking fault energy of the parent phase by nitrogen alloying. A coupled stacking faulting-modulus softening mechanism is proposed as the modification of the currently accepted faulting mechanism for the ɛ martensite nucleation.

Martensitic microstructure and its damping behavior inNi52Mn16Fe8Ga24single crystals

In the present study, the martensitic microstructure and its damping behavior in ${\mathrm{Ni}}_{52}{\mathrm{Mn}}_{16}{\mathrm{Fe}}_{8}{\mathrm{Ga}}_{24}$ single crystals were investigated using differential scanning calorimetry (DSC), x-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamical mechanical analyzer (DMA). A structural transition from the cubic austenite to orthorhombic seven-layered modulation martensite was confirmed by XRD experiments and TEM observations. The measurements of temperature dependence of internal friction (IF) reveal an additional very broad IF peak in the low-temperature martensite phase. Moreover, the IF peak is frequency independent but it shows a pronounced amplitude dependence behavior, i.e., the IF peak broadens, decreases in height, and shifts to lower temperature with the increase of amplitude. The related mechanisms are also discussed in terms of the martensitic microstructure.

Reconsideration of Anelastic Relaxation Peaks in PureAluminium

The temperature dependence of internal friction (T−tan φcurves) in pure aluminium (Al) is measured at sixteen differentfrequencies. Based on T−tan φ curves, the frequencydependence of internal friction (f−tan φ curves) is alsoobtained by the interpolation method. An internal friction peak isobserved in both the T−tan φ curves and the f−tan φ curves. Theactivation energy of the peak in the f−tan φ curves is found to be2.08±0.02 eV and compared to the value of 1.60±0.04 eV inthe T−tan φ curves. It is suggested that the change of relaxationstrength with temperature should be considered when one calculates theactivation energy of the peak in T−tan φ curves.

The effect of oxygen content on the magnetic cluster in the paramagnetic region of La0.67Ca0.33MnOy

We have measured the temperature dependence of internal friction Q−1(T), Young's modulus E(T), and resistivity ρ(T) in situ along with the measurements of magnetization M(T) on optimally doped manganites La0.67Ca0.33MnOy with different oxygen contents. With the reduction of the oxygen content y, the Q−1 peak in the paramagnetic region, suggested to originate from the formation of the magnetic clusters (MC), shifts to a lower temperature and its magnitude decreases and finally disappears. The results of M(T) and ρ(T) indicates that both the effective magnetic moment μeff and the hopping distance of electrons decrease with the increase of oxygen vacancies, which may suppress the MC. In addition, the analysis of the results of E(T) indicates that the cooperative effects of lattice distortions may favour the formation of MC.

Stability and hydrogen-induced internal friction of Ti-rich multicomponent glassy alloys

Hydrogen-induced internal friction behavior of ternary Ti 37 Zr 12 Cu 51 and quaternary Ti 34 Zr 11 Cu 47 Ni 8 , which is also expressed by (Ti 0.37 Zr 0.12 Cu 0.51 ) 92 Ni 8 , glassy alloys with a wide supercooling region have been investigated by measuring temperature dependence of internal friction above 90 K. It is found that they show a broad peak depending hydrogen content. With increasing hydrogen content, the peak internal friction of both glassy alloys increases, while the peak temperature decreases. It should be noted that the peak internal friction of quaternary Ti 34 Zr 11 Cu 47 Ni 8 glassy alloys are larger than that of ternary Ti 37 Zr 12 Cu 51 glassy alloys in the hydrogen content dependence of the peak internal friction. This is attributable to the increase of local strain anisotropy due to the change of local atomic arrangement when adding Ni, i.e. the change from ternary to quaternary. On the other hand, there are no distinguished effects of the change on the hydrogen content dependence of the peak temperature, suggesting changes not only the activation energy but also the frequency factor (pre-exponential factor) in the relaxation process by the change.

Modulus characteristics during the γ→ε martensitic transformation in Fe–Mn–Si–Cr–N alloys

The temperature dependences of internal friction and modulus were measured for the Fe–Mn–Si–Cr– xN alloys. A stable modulus softening of parent was newly observed to associate with the γ→ε martensitic transformation in the alloys containing certain amount (e.g. >0.086 mass%) of nitrogen, although the rather strong softening has been always recognized to occur during its reverse transformation. The enhanced strength and the increased stacking fault energy of γ matrix by nitrogen alloying are suggested to make contribution to the soft mode.