Internal Friction Background Research Articles

High-temperature background of internal friction in alloys

Experimental results for the high-temperature background of internal friction in solids are analyzed. Common features are noted for the high-temperature background of internal friction in solids independent of structure. The exponential increase observed in internal friction is associated with point defect migration.

Anelastic Effects of Phase Decomposition in 14-Carat AuAgCu Alloy

A relaxation peak has been observed in the internal friction spectrum of 18-carat AuAgCu yellow gold alloys at about 750K for 0.5Hz. It is related to the presence of grain boundaries, since it is absent in the spectrum of single crystals. For the 14-carat yellow gold alloy (Au38%Ag32%Cu30%), a phase decomposition between silver-rich and copper-rich solid solution occurs in the same temperature range. The effects of the phase decomposition on the internal friction and the dynamic modulus are studied by isochronal and isothermal measurements and correlated with the microstructure evolution. Upon cooling, the phase decomposition starts at grain boundaries at about 840K, producing a fine lamellar structure, and the grain boundary peak amplitude strongly decreases. As the phase decomposition progresses at the interior of the grains upon further cooling, the internal friction background increases. It remains very high in heating until solid solution homogenisation, which occurs above 890K. Such an increase of the internal friction background is observed also in the single crystalline alloy and may be attributed to the interfaces between lamellae of the silver and copper-rich phase.

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.

An Ultra-High <i>Q</i> Silicon Cantilever Resonator for Thin Film Internal Friction and Young's Modulus Measurements

An audiofrequency (8.5 kHz) cantilever resonator with an extremely low background internal friction (Q-1≈2×10-8) at liquid helium temperatures has been developed. Above 30 K, theQof the resonator is dominated by thermoelastic loss;Q-1is nearly exactly described by Zener’s formula for thermoelastic damping. Below 30 K,Q-1decreases monotonically with decreasing temperature, reaching a typical baseline ofQ-1=1.5×10-8at 400 mK.

Temperature dependence of internal friction in enzyme reactions

Our aim was to elucidate the physical background of internal friction of enzyme reactions by investigating the temperature dependence of internal viscosity. By rapid transient kinetic methods, we directly measured the rate constant of trypsin 4 activation, which is an interdomain conformational rearrangement, as a function of temperature and solvent viscosity. We found that the apparent internal viscosity shows an Arrhenius-like temperature dependence, which can be characterized by the activation energy of internal friction. Glycine and alanine mutations were introduced at a single position of the hinge of the interdomain region to evaluate how the flexibility of the hinge affects internal friction. We found that the apparent activation energies of the conformational change and the internal friction are interconvertible parameters depending on the protein flexibility. The more flexible a protein was, the greater proportion of the total activation energy of the reaction was observed as the apparent activation energy of internal friction. Based on the coupling of the internal and external movements of the protein during its conformational change, we constructed a model that quantitatively relates activation energy, internal friction, and protein flexibility.

Nanostructure Characterization of Bismuth Telluride-Based Powders and Extruded Alloys by Various Experimental Methods

High-resolution transmission electron microscopy (HRTEM) observations of mechanically alloyed powders and bulk extruded alloys give experimental evidence of nanosized grains in bismuth telluride-based materials. In this study we combine HRTEM observations and x-ray diffraction (XRD) measurements, of both mechanically alloyed powders and extruded samples, with mechanical spectroscopy (MS) of extruded rods. Both HRTEM and XRD show that nanostructures with an average grain size near 25 nm can be achieved within 2 h of mechanical alloying from pure elements in an attritor-type milling machine. Residual strain orthogonal to the c-axis of powder nanoparticles has been evaluated at about 1.2% by XRD peak broadening. In contrast, XRD has been found unreliable for evaluation of grain size in highly textured extruded materials for which diffraction conditions are similar to those of single crystals, while MS appears promising for study of bulk extruded samples. Nanostructured extruded alloys at room temperature exhibit an internal friction (IF) background that is one order of magnitude higher than that of conventional zone-melted material with a grain size of several millimeters. IF as a function of sample temperature gives activation energies that are also different between bulk materials having nano- and millimeter-size grains, a result that is attributed to different creep mechanisms. Nanograin size, as well as orientation and volumetric proportion, provide valuable information for optimization of technological parameters of thermoelectric alloys and should be carefully cross-examined by various independent methods.

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.

Effect of precipitation on internal friction of AZ91 magnesium alloy

The effect of precipitation on the internal friction (IF) of AZ91 magnesium alloy was investigated by using X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) observation, and dynamic mechanical analysis (DMA). Six different states of alloy were prepared by applying different heat treatment processes: as-cast, in-complete solid solution, complete solid solution, micro-precipitation, continuous precipitation and continuous–discontinuous precipitation. It was found that the internal friction of in-completely solid-solutionized, completely solid-solutionized and micro-precipitated specimens showed a similar characteristic, and the grain boundary relaxation is completed depressed due to the Al atoms supersaturated in the α-Mg solution. However, a thermal relaxation internal friction peak was observed for continuously precipitated and continuously– discontinuously precipitated specimens at around 438 K and frequency of about 1 Hz, which was attributed to the grain boundaries relaxation. Furthermore, it was found that the relaxation of the β-Mg 17Al 12/ α-Mg phase interfaces should give its contribution to the background internal friction in the as-cast, continuously precipitated and continuously–discontinuously precipitated specimens.

High-temperature relaxation analysis in a fine-grain B2 FeAl intermetallic

The study of anelastic relaxation by means of mechanical spectroscopy gives a unique insight into the mechanisms of defect mobility, and provides crucial information for the development of new intermetallic materials. In this work, a new high-temperature mechanical spectrometer, working up to 1800 K, is used to perform such study in order to better understand the underlying processes controlling plasticity in an advanced Fe-38% Al intermetallic. The measured internal friction spectra, as a function of temperature for different frequencies, show one internal friction peak at about 1100 K with a background increasing exponentially with temperature up to 1350 K. In this work we apply a model that gives a consistent description of the high-temperature internal friction background in order to obtain the parameters characterizing the involved relaxation processes: H act = 5.4 ± 0.2 eV and τ 0 = 1.4 × 10 −19 s. This apparent activation energy of the high-temperature background is compared with results in the literature obtained by creep tests and discussed in terms of the possible microscopic mechanisms. Moreover, the subtraction of the obtained background allowed a more precise measure of the activation enthalpy for the 1100 K relaxation peak: H peak = 2.98 ± 0.02 eV. We conclude that the mechanisms operating in this temperature range should be related to those controlling creep in these materials.

High-temperature internal friction in a Fe–38 at.% Al intermetallic

A new sub-resonant inverted torsion pendulum has been used to measure the internal friction and dynamic modulus of an Fe–38 at.% Al alloy as a function of temperature from 600 to 1350 K and constant oscillating frequency ranging from 0.01 to 3 Hz. Two internal friction peaks and a background increasing exponentially with temperature were observed. Both peaks overlap and have different shifts to lower temperatures with decreasing frequency indicating different involved relaxation mechanisms. We measured the activation parameters of the main peak. Finally we applied a recently proposed model to remove the high-temperature internal friction background and perform a spectra de-convolution to find the parameters characterizing both relaxations. The mechanisms responsible for both relaxations are discussed.

Internal friction characterization of graphite

The effects of temperature on the damping behavior of bulk graphite were investigated and some novel phenomena were observed. The internal friction (IF) background of the bulk graphite has small temperature dependent and the IF value is much smaller than that of reported data. Moreover, two IF peaks were found in the IF-temperature spectrums. The first is proved to originate from the sweeping motion of in-plane dislocations and is a relaxation-type IF peak. The average activation energy of the peak is around 1.10 ± 0.06 eV and the pre-exponential factor τ 0 is 10−14 s. The second is a transformation peak, resulting from the transformation of asphalt that was used as binder in preparation of bulk graphite.

High-Temperature Internal Friction of Metallic Glasses with Widely Different Glass-Forming Ability

The internal friction (IF) of binary, ternary, quaternary, and quinary metallic glasses with widely different glass-forming ability (GFA) has been studied. A single-roller melt-spinning apparatus was used for preparing ribbon specimens. An inverted torsion pendulum was used in the IF measurement. The measurements were performed from room temperature, through the glass transition temperature, up to the crystallization temperature. The background IF monotonously increases with increasing temperature. The increase is of the thermal-activation type, and the activation energy E is determined. For alloys with higher GFA, the E value tends to be higher. IF is inversely proportional to the measurement frequency. The viscosity relaxation based on the Maxwell model is considered, and the relaxation time τ is determined. A linear relationship is seen between the logarithm of pre-exponential factor τ o and the activation energy E . Explanations of these results and discussions concerned are presented.

Internal Friction Behaviors of TiNi Shape Memory Alloy Fiber/Ni Matrix Composite

The objective of present work is to investigate the internal friction behavior of TiNi shape memory alloy fiber/Ni matrix composite. The TiNi fiber/Ni matrix composite was fabricated by an electroplating method using TiNi alloy fiber as the cathode and Ni plate as the anode. The internal friction as functions of temperature and strain amplitude was measured respectively. The results showed that the internal friction peaks of the TiNi/Ni matrix composites, which due to the martensitic reverse transformation of the TiNi fiber, broadened with increasing prestrain level. There was a sharp internal friction increment at the high temperature, which due to thermal expansion mismatch between the TiNi fiber and Ni matrix and recovery stress generated. Contrast to the pure TiNi alloys, the internal friction background of the TiNi/Ni composites increased with increasing temperature. Furthermore, the internal friction of the TiNi/Ni composites decreased with increasing strain amplitude measured.

Effects of macroscopic graphite particulates on the damping behavior of CuAlMn shape memory alloy

A novel composite was fabricated using a Cu-11.9Al-2.5Mn (wt%) shape memory alloy as the matrix and macroscopic graphite particulates as the second phase. The damping behavior of the resultant composite was examined in the present study through internal friction measurements. It was found that the net height of the internal friction peak relating to phase transformation decreased in the composite due to the constraining effect of the particulates, but the internal friction background significantly increased with increasing the volume fraction or decreasing the diameter of the particulates, giving rise to an improved damping capacity particularly at low temperatures. It is proposed that the interface damping, dislocation damping and the intrinsic damping of the matrix and the constraint are predominant in the composite.

Damping behavior of porous CuAlMn shape memory alloy

Internal friction measurements were conducted to examine the damping behavior of a porous Cu–11.9Al–2.5Mn (wt.%) shape memory alloy. It is found that the internal friction background significantly increased with increasing volume fraction or decreasing diameter of the pores due to stress concentration and mode conversion around pores when loaded, the refined microstructures and increased dislocation population.

Search for High Damping Metallic Glasses

In a hydrogen-doped metallic glass, there appear low-temperature and high-temperature internal friction peaks respectively associated with a point-defect relaxation and the crystallization. The high-temperature-side slope of low-temperature peak and also the low-temperature-side slope of high-temperature peak enhance the background internal friction near the room temperature. A hydrogen-doped Mg-base metallic glass was proposed as a high-damping material to be used near and somewhat above the room temperature. Stability of the high damping was also checked.

Low-temperature relaxation in faulted Cu-based martensites

An extensive investigation of elastic and anelastic properties, at an ultrasonic frequency of around 100 kHz, of a variety of binary and ternary Cu-based alloys forming faulted martensites evidences the existence of a strong anelastic relaxation over a wide temperature range propagating down to lowest temperatures achieved in experiments of around 10 K. The anelastic phenomenon observed is the most pronounced for low oscillatory strain amplitudes (approximately from 10 −7 to 10 −6) and results in a rapid decrease of Young's modulus (measured at low strain amplitudes) with increasing temperatures from the lowest values of around 10 K. The relaxation of Young's modulus is accompanied by a linear increase of the low-amplitude internal friction with increasing temperature. The low-temperature relaxational behaviour is strongly dependent on concentration of quenched-in vacancies: the relaxation is enhanced by β-phase ageing and is strongly suppressed by direct quenching of ternary Cu–Al–Ni, Cu–Zn–Al and Cu–Al–Be alloys. The anelastic effect observed exhibits an unusual property: the amplitude-independent internal friction background emerging as a result of this relaxation is non-additive with the amplitude-dependent internal friction. We suggest that this low-temperature relaxation is associated with a reversible transition from a cooperative to an individual mode of motion of the system of partial dislocations.

Correlation between internal friction background and the concentration of carbon in solid solution in a martensitic steel

A martensitic carbon steel was tempered in successive steps in order to vary the concentration of carbon in solid solution in the martensite. The actual solute content was assessed by thermoelectric power and X-ray diffraction. Internal friction was measured in a vibrating reed apparatus and in a torsion pendulum. The internal friction level around room temperature shows a surprising linear correlation with the carbon content even in the absence of the Snoek peak. This internal friction level is attributed to long-range interaction of edge dislocations with carbon in solid solution.

Thermal stresses in a macroscopic graphite particulates reinforced CuAlMn shape memory alloy studied by internal friction

In the present study, a novel metal matrix composite (MMC) has been fabricated with a Cu–11.9Al–2.5Mn (wt%) shape memory alloy (SMA) and macroscopic graphite particulates with the objective of damping enhancement. The functional properties of such MMC are directly related to the constraining behavior that the composite reinforcement has on the SMA. Following temperature changes large internal stress can be induced due to the difference in coefficient of thermal expansion (CTE) between reinforcement and matrix, resulting in the change of the configuration of martensite variants or the microplastic deformation of the matrix, leading to the appearance of high dislocation density. The damping behavior of the novel MMC has been measured using a multifunction internal friction apparatus (MFIFA) through the method of forced vibration at low frequencies of 0.5, 0.8 and 1.0 Hz. In addition to the remarkable elevation of the internal friction background an internal friction peak appears at around 240 °C, while it is absent for the corresponding block CuAlMn alloy. The internal friction peak has been attributed to the interaction between the dislocations and the cyclic stress applied during internal friction measurement.

Effects of quenched‐in vacancies on the damping behaviour of Cu–11.9Al–2.5Mn shape memory alloy

AbstractBy internal friction technique, the behaviour of quenched‐in vacancies and their influence on the martensitic transformation of the Cu–11.9Al–2.5Mn alloy has been studied. It is found that the reverse martensitic transformation temperature Tp follows a non‐monotonous dependence on quenching temperature Tp, of which the presence of a maximum Tp value is attributed to the different vacancy formation energies in the ordered and disordered phases. The background internal friction decreases with increasing ageing time due to migration of vacancies and resultant pinning effect on the phase interfaces and dislocations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)