High Temperature Internal Friction Peak Research Articles

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.

Anelastic Properties of Mg+3vol.%Gr Prepared by Ball Milling

Internal friction in ultra-fine grained Mg with 3vol% of Graphite was measured by forced vibration method at low frequencies of 0.1, 0.5, 1.0, and 2.0 Hz over a temperature range from room temperature to 753 K with continuous heating. The specimens were prepared by milling procedure in an inert atmosphere and subsequent compacted and hot extruded. Two developed peaks in the internal friction spectrum were obtained at temperatures ≈ 350 K and ≈ 550 K. While the position of the first peak is frequency dependent, the second peak position is stable, independent of measuring frequency. The activation energy of the low temperature peak was estimated. In the light of internal friction measurements, the high temperature internal friction peak is attributed to the generation and motion of dislocations produced by the difference in the coefficient of thermal expansion between the Mg matrix and Gr phase at the matrix–particle interfaces.

Activation volumes and site relaxation in mixed alkali glasses

Evidence is presented for site relaxations occurring in mixed alkali (cation) glasses based on activation volumes, VA(σ)=−RT[dlnσ/dp]T, which are determined for sodium aluminoborate glasses of varying Na2O content, and for mixed alkali glasses where Na+ is partially replaced by Li+, K+ or Cs+ ions. In accordance with the ‘updated’ dynamic structure model, activation volumes are identified here with local expansions that accompany the opening up of C′ sites to admit incoming ions. ‘Anomalous’ increases in activation volume in mixed cation glasses correlate with the size of minority (guest) cations. This anomaly is interpreted in terms of a ‘leader follower’ mechanism that involves dynamic coupling between the faster (majority) and slower (minority) cations. Because of mismatch effects in mixed cation glasses this coupling requires the opening up of additional cation sites by the slower follower cations. The resulting disturbances in the glass network are responsible for many characteristic features of the mixed alkali effect, including the appearance of high temperature internal friction peaks and observed minima in glass transition temperatures and melt viscosities.

Effects of macroscopic bulk defects on the damping behaviors of materials

A large number of macroscopic pores or graphite particulates were introduced into commercially pure Al and ZA27 alloy by infiltration process to comparatively study the influence of macroscopic defects on the damping behaviors of the materials. The mean diameter of the bulk defects is (1.0±0.5) mm, and the volume fractions of pores and graphite particulates are in the range of 50%—75% and 19%—94%, separately. It is shown that addition of a number of pores or graphite particulates can significantly improve the damping of commercially pure Al, due to the comprehensive effects of the macroscopic and microscopic defects. However, the pores have little effect on the damping capacity of high damping ZA27 alloy, and graphite particulates make the high temperature internal friction peak decrease. It is considered that graphite particulates may repress the intrinsic damping mechanism of ZA27 alloy.

High-temperature internal-friction peak in as-quenched bamboo crystalline aluminium

Abstract Soon after the discovery of the bamboo internal-friction peak (the BB peak) in bamboo crystalline aluminium, a new high-temperature internal-friction peak (designated the HT peak) was observed at a higher temperature when the specimen was quenched from high temperatures. Previous experiments with internal friction measured by the free-decay method showed that this peak is characterized by its high relaxation strength and high activation energy and it exhibits an anomalously amplitude-dependent effect. In this paper, these manifestations are critically studied by measuring the internal friction with the forced-vibration method. This HT peak is found to consist of two subpeaks, designated the HT-1 and HT-2 peaks respectively. The activation energy of the HT-1 peak is found to be 1.4 eV and the activation energy of the HT-2 peak is 2.1 eV. On the basis of the results of the transmission electron microscopy observation, it is suggested that the higher-temperature subpeak (the HT-2 peak) is attributed...

Anomalous non-linear amplitude effect associated with the high-temperature internal friction peak in as-quenched high-purity aluminium

Anomalous non-linear amplitude effect associated with the high-temperature internal friction peak in as-quenched high-purity aluminium

High-temperature internal friction peak in high-purity aluminium associated with quenching from high temperatures

High-temperature internal friction peak in high-purity aluminium associated with quenching from high temperatures

High-Temperature Internal Friction Peak in Al–0.008 wt% Sn Single Crystals

Internal friction of Al–0.008 wt% Sn single crystals prepared by the dynamic-annealing method is measured using an inverted torsion pendulum. Within the temperature range from 250 to 310°C, an internal friction peak which grows with annealings at 510°C accompanied by the displacement of the peak to higher temperatures is observed for the first time when the frequency of vibration is about 1.3 Hz in the experiments. This peak becomes stable after the specimen is annealed at 510°C for about 10 h, with parameters as follows: peak temperature 305°C, peak height 0.057, and activation energy 1.1 eV. Effects of quenching, aging, twisting, and stretching on this peak are also investigated. A preliminary analysis shows that this peak is originated by pipe diffusion of tin atoms along dislocations. Mit einem invertierten Torsionspendel wird die innere Reibung von Al–0,008 Gew% Sn-Einkristallen gemessen, die mittels dynamischer Temperungsmethode hergestellt werden. Im Temperaturbereich von 250 bis 310°C wird erstmalig ein Reibungsmaximum beobachtet, das mit Temperung bei 510°C anwachst, begleitet von einer Verschiebung des Maximums zu hoheren Temperaturen, wenn die Schwingungsfrequenzen etwa 1,3 Hz in den Experimenten betragt. Dieses Maximum wird stabiler, wenn die Probe bei 510°C etwa 10 h getempert wird, mit folgenden Parametern: Maximumtemperatur 305°C, Maximumhohe 0,057 und Aktivierungsenergie 1,1 eV. Einflusse von Abschrecken, Alterung, Verdrillung und Dehnung auf dieses Maximum werden ebenfalls untersucht. Die vorlaufige Analyse ergibt, das dieses Maximum durch Pipe-Diffusion von Zinnatomen langs Versetzungen verursacht wird.

Reply to the comments by leighly Jr. on high-temperature internal friction peak in aluminium

Reply to the comments by leighly Jr. on high-temperature internal friction peak in aluminium

Variations of internal friction in YBa2Cu3Ox superconductors

The internal friction (Q−1) spectrum of YBa2Cu3Ox superconducting ceramic exhibits several peaks. It has been confirmed that the high-temperature peak (around 240 K) depends on structural changes and varies during subsequent cycles of cooling and heating.Q−1 conductivity, X-ray spectra and the shielding effect have been measured on several samples having different superconducting properties obtained by various thermal treatments. Splitting is a characteristic feature of the high-temperature internal friction peak of the sample which exhibits good superconducting properties. In the case of the specimen exhibiting the worst properties the peaks decrease and overlap. In both cases an increase can be observed of this peak with the number of thermal cycles. After ageing at 470 K, the high-temperature peak disappears. Subsequent thermal cycles slightly recover it. Hysteresis of the Young modulus is also observed. The results are interpreted as transition of the 04 oxygen atom between two energy minima in the O4-Cu-O4 chain.

Origin of the high temperature internal friction peak introduced by twisting deformation in aluminium single crystals and bamboo crystals

The internal friction peak appeared around 310°C (l Hz) in single crystals and bamboo crystals of high-purity aluminium introduced by twisting deformation as previously reported has been further studied especially concerning its relaxation properties. This peak is thermally-activated having a very high relaxation strength up to 0.3 and a very high activation energy of about 2 eV. The fact that the peak disappears after rapid cooling of the specimen leads to the proposition that dislocation climb does not play a dominating role to the non-elastic motion of the dislocations giving rise to this peak. TEM observations show that the stable dislocation configuration in the twisted specimen after the 600°C anneal always consists of uniformly distributed dislocation networks. Subsequent tensile deformation destructs such dislocation networks and converts it into cell structures so that the twisting peak is suppressed. It is suggested that the dislocation slip enhanced by the non-conservative shift of the node of the dislocation network contributes dominately to the high relaxation strength of the twisting peak and the dislocation climb controls the relaxation time of the relaxation process.

High temperature internal friction peak in single-crystals and bamboo-crystals of aluminium after twisting and annealing

A high temperature internal friction peak has been observed around 310°C (1 Hz) in single crystals and bamboo crystals of 99.999 wt% aluminium after twisting and annealing at high temperatures. This peak appears only when internal friction measurements are performed in torsional vibration but not in longitudinal vibration mode. A tensile deformation applied afterward suppresses this peak. In the case of stretched specimens, no peaks were observed within the temperature region of the twisting peak. However the high temperature background is slightly raised in measurements performed both in torsional and longitudinal vibration modes. Laue pattern for twisted and stretched specimens examined after internal friction measurements are remarkably different. Preliminary analysis suggests that the stress field introduced by tensile deformation is localized and isotropic while that introduced by twisting deformation is long ranged and anisotropic. Consequently each stress field has its characteristic interaction with the stress field applied during internal friction measurements in torsional and longitudinal vibration modes and gives rise to different relaxation processes.

High Temperature Internal Friction Peak in High Purity Single Crystal Aluminium Sheets and Electron Microscopic Observation on the Related Dislocation Configurations

Electron microscopic observations on films from 99.999 wt%, thinned down aluminium single crystal sheets after internal friction measurements shows that the dislocation configuration responsible for the appearance of the internal friction peak (400 °C, f = 1.3 Hz) is a uniformly distributed spatial dislocation network and the disappearance of this peak after tensile deformation is due to the breakdown of this network and the occurrence of some kind of cell structure. Discussions are made on the cautions to be taken in correlating the results of internal friction measurements and electron microscopic observations.

Crystallization behaviour near the high temperature internal friction peak of a-Pd80Si20 alloy

The crystallization behaviour of a-Pd80Si20 in the high temperature internal friction peak region is systematically studied by DSC and x-ray diffraction techniques.

High-temperature internal friction peaks of dilute aluminum alloys

Internal friction of dilute aluminum alloys is measured with an inverted torsion/flexure pendulum. The effects of solute addition are as follows. (i) The grain boundary peak is shifted to higher temperature. (ii) The low-temperature peaks around 100 °C are suppressed. (iii) Two additional peaks are observed at about 400 and 500 °C. The strength of these effects depends on the kinds of solutes. The experimental results are explained by the preferential segregation of solutes on grain boundaries and dislocations. Die innere Reibung von verdunnten Aluminium-Legierungen wird mit einem inversen Torsions-oder Biegungspendel gemessen. Die Einflusse der Fremdatome sind folgende: (i) Das Korngrenzen-maximum ist nach hoheren Temperaturen verschoben. (ii) Die Tieftemperaturmaxima bei etwa 100 °C werden unterdruckt. (iii) Zwei neue Maxima werden bei etwa 400 und 500 °C beobachtet. Die Starke dieser Effekte ist von den Fremdatomarten abhangig. Diese experimentellen Ergebnisse werden durch bevorzugte Segregation der Fremdatome an Korngrenzen und an Versetzungen crklart.

High-Temperature Internal Friction Peaks of Pure Aluminum Single-, Bi-, and Polycrystals Measured with an Inverted Flexure Pendulum

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High-Temperature Internal Friction Peaks of Pure Aluminium

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Deformation and annealing effects on high-temperature internal friction peaks of aluminium single and polycrystals

Two peaks, K1 and K2, in place of the Kě one, are found by low amplitude internal friction measurements on annealed Al polycrystals. These K-peaks probably depend on dislocation damping since they appear also with bent single crystals having only dislocations, free or in polygonization walls. This view is supported by the occurrence of modulus defects corresponding to the K-peaks also with non-deformed single crystals, having only free dislocations. The activation energies of the two peaks are comparable with those characterizing Al creep above room temperature. Zwei Maxima. K1 und K2, werden im Gegensatz zu Kě bei Messungen der inneren Reibung beikleinen Amplituden an getemperten Al-Polykristallen gefunden. Diese K-Maxima hängen wahrscheinlich von der Versetzungsdämpfung ab, da sie auch in gebogenen Einkristallen auftreten, die nur Versetzungen, frei oder in Polygonisierungswänden, besitzen. Diese Ansicht wird bestätigt durch das Auftreten von Elastizitätsmoduldefekten, die den K-Maxima entsprechen, auch in nicht-verformten Einkristallen, die nur freie Versetzungen besitzen. Die Aktivierungsenergien dieser beiden Maxima sind vergleichbar mit denen, die Al-Kriechen oberhalb Zimmertemperatur beschreiben.