Dependent Internal Friction Research Articles

A study of softening processes in heating of cold-deformed sheets of low-alloy aluminum alloys

Processes of polygonization and recrystallization in aluminum alloys with 0.3 at.% magnesium, zinc, or copper and their structure and hardness are investigated. The temperature, time, and amplitude dependences of internal friction are determined. A comparative analysis of the dislocation structure in the alloys is conducted.

On combining high damping capacity and high strength in nanocrystalline materials

Nanocrystalline materials obtained by the method of severe plastic deformation are studied. Successive recrystallization annealing operations are used to form different structural states in specimens. Tensile tests and measurements are performed to determine the amplitude and temperature dependences of internal friction in specimens of copper and stainless steel.

Effect of microadditions of magnesium and zinc in aluminum upon heating of cold-rolled sheets

Methods of structural investigations, measurements of hardness, temperature, time, and amplitude dependences of internal friction have been used to study processes of polygonization and recrystallization in Al-0.3 at % Mg and Al-0.3 at % Zn alloys. It has been established that the magnesium atoms more efficiently pin dislocations in the aluminum-based alloys as compared to zinc atoms. Therefore, in the alloy with zinc the process of polygonization occurs more intensely and the processes of softening upon recrystallization occur more slowly than those in the alloy with magnesium.

Improved mechanical property and internal friction of pure Mg processed by ECAP

Equal channel angular pressing was performed on the extruded pure Mg. The elongation to failure of the ECAPed pure Mg is enhanced to 27% without sacrificing the strength, which is mainly resulted from both the effective refinement of grain size and the weakening of the basal plane texture. The internal friction mechanisms of magnesium at room and elevated temperature were studied by dynamic mechanical analyzer (DMA). The strain independent internal friction is increased after ECAP processing, while the strain dependent part is obviously decreased. Three internal friction peaks were observed in the temperature dependent internal friction curves. The activation energy is 105kJ/mol for P1 peak, which may be related to the basal dislocation glide controlled by climb of jogs and diffusion of vacancies along dislocations. The activation energy of P2 peak is in the range from 95 to 181kJ/mol, and this obviously broadened peak is associated with grain boundary relaxation. The P3 peak is related to recrystallization.

Internal friction in (Fe80Ga20)99.95(NbC)0.05 alloy at elevated temperatures

The temperature and frequency dependent internal friction of a rolled (Fe80Ga20)99.95(NbC)0.05 alloy has been investigated using computer-controlled automatic inverted torsion pendulum instruments. The measurements were carried out in forced vibration mode from room temperature up to 973 K with frequency varying between 0.5 Hz and 11 Hz. Results obtained by standard methods of XRD, SEM and DSC show that the main phases in the specimen structure is the disorder A2 phase (random solid solution) and the NbC phase. Two internal friction peaks are observed in the temperature range from room temperature to 973 K. The low-temperature peak at about 423 K occurs only at high quenching temperature and may be a complex effect consisting of Snoek-type relaxation and vacancies/ordering effect. A pronounced thermally activated relaxation peak (P1) at about 750 K observed in all samples with activation energy of 2.21–2.84 eV and relaxation time of 1.71 × 10−20–8.79 × 10−17 s is classified as the Zener peak. The high damping background above P1 is caused by the interaction between NbC precipitates and Ga solution particles at high temperature. The high temperature peak (P2) at about 873 K is only observed in samples water quenched below 1173 K. The P2 peak disappears if the samples are water quenched from temperature above 1373 K. The P2 peak height is strongly dependent on annealing temperature and the damping background decreases quickly with increasing temperature. According to activation energy, the P2 peak is most probably originating by grain boundary relaxation. In particular, the particles on the grain boundaries lead to grain boundary relaxation.

Martensitic transformation and precursor phenomena in Au7Cu5Al4 alloys

Abstract The β (body centered cubic) phase in Au 7 Cu 5 Al 4 alloys is known to give a displacive martensitic transformation associated with shape memory effect and an interesting surface texture known as ‘Spangold’, as well being considered as a good candidate for biomedical implant applications due to gold being biocompatible and radio-opaque. Studies have been carried out on the martensitic transformation and precursor phenomena in three Au–Cu–Al alloys near Au 7 Cu 5 Al 4 composition, for the temperature ranging from 200 to −100 °C by means of dynamic mechanical analysis. Frequency dependent internal friction peaks have been observed for both cooling and heating processes in two of these alloys, which are associated with the glass behavior. The glassy state in Au 7 Cu 5 Al 4 alloys is a type of precursor phenomenon followed by martensitic transformation. Different defects or phases resulting from the different composition are believed to play a key role in the manifestation of a glass behavior.

Dynamical mechanical behaviors of Ce-based bulk amorphous alloy

The mechanical relaxation of Ce70Al10Cu20 bulk amorphous alloy has been investigated isothermally by dynamic mechanical analysis (DMA) from -70℃ to 70℃ in a frequency sweep mode. Our results show that the frequency- dependent internal friction curve has two different tendencies in the whole frequency range. The internal friction values decrease with frequency rising in the low frequency range, but increase in the high frequency range. It is proposed that these two different mechanical relaxations come from the different local structures in the metallic glass.

Internal friction study of the stress relaxation behavior in Cu–Ni–P alloys

The strain-amplitude dependence of internal friction in Cu–Ni–P alloys has been investigated to evaluate nondestructively the stress relaxation resistance. Annealing at 250 °C after cold rolling causes a suppression of the strain-amplitude dependence with increasing annealing time in the range between 10 and 10 4 s. It is revealed that the stress relaxation resistance linearly improves as the microplastic strain evaluated from the amplitude-dependent internal friction decreases.

Investigation of the Nanostructures Formation in the Irradiated by γ-Quanta Single-Crystal Silicon with Ultrasonic Method

It’s determined that a phasic dynamics of deformation strengthening of single-crystal silicon irradiated by γ-quanta (with energy ~1.27 MeV) in the range of radiation absorbed doses from 102 up to 109 rad by the internal friction measurement with widely known ultrasonic resonance method. We have detected appearance the maximum on the dependence of internal friction (Q-1) from dose at 5 × 105 rad in the specimens of p - Si with a density of the dislocations more than 103 cm-2. The instability of the dislocation structures has been established in the range of doses from 106 up to 109 rad, due to the formation and accumulation in the crystal lattice of the point like and the continuous radiation defects. On the time dependence of Q-1(t) per 1.5 - 2 hours after irradiation, the maximum has been established which position depends on dose of radiation. The monotonic decrease of Q-1(t) dependence was observed at the increase of the observation time after stopping of the specimen irradiation, which is connected with decreasing of the radiation defects densities as the result of their annihilation.

Stress Relaxation Behavior of Cu-Ni-P Alloys Evaluated from Amplitude-Dependent Internal Friction

The strain-amplitude dependence of internal friction in Cu-0.41Ni-0.11P (mass%) alloys has been evaluated to reveal the relation between the amplitude-dependent internal friction and the stress relaxation performance. Annealing at 250°C after cold rolling causes a suppression of the strain-amplitude dependence with increasing annealing time in the range between 10 s and 104 s. Analysis of the amplitude-dependent internal friction reveals the plastic strain of the order of 10-9 as a function of effective stress on dislocation motion. It is found that the microflow stress at a constant level of plastic strain increases with increasing annealing time. This result is in line with the improvement in the stress relaxation performance but disagrees with a decrease in the tensile strength and yield stress after annealing. We believe that the increase in the microflow stress after annealing is caused by inhibition of dislocation motion due to Ni-P clusters, which were revealed by three-dimensional atom probe (3DAP) experiments.

Mechanical Spectroscopic Study of Equal-Channel Angular Pressed Al-Ni Eutectic Alloy

In this study, temperature dependence of internal friction, tand, of ECAPed Al-Ni eutectic alloy was measured using a dynamic mechanical analysis (DMA) to discuss the recrystallization behavior of the alloy. The temperature dependence of internal friction of 8 passed samples shows a large peak at around 200 °C on heating, while this peak disappears on the subsequent cooling stage. Moreover, smaller peak was observed for 2 passed samples. Therefore, it can be concluded that the origin of the peak comes from the recrystallization of a-Al.

Effects of Pinning and Atomic Ordering on Damping Properties and Martensitic Transformation of Copper-Based Shape Memory Alloys

The effects of long-range atomic order and pinning of interfaces on anelastic properties of Cu-based martensite have been distinguished by means of studying strain amplitude dependences of internal friction and Young’s modulus defect, assuming that low-and high-amplitude stages of the strain amplitude dependence correspond to the oscillations within and beyond pinning atmospheres.

Amplitude Dependent Damping of Aluminum-Matrix-Nanoparticle-Composites

Aluminum-matrix-nanoparticle-composites were produced by ball milling of micro scale aluminum powder in air atmosphere with subsequent consolidation by hot extrusion and also additional hot swaging. They were investigated in this condition after step by step isochronal annealing with successive increasing annealing temperature and quenching into water to room temperature. The material was investigated by amplitude dependent damping, hardness and density measurements, all at room temperature. For all measured amplitude dependent internal friction (ADIF) curves the damping increases with increasing strain amplitude. After some annealing treatments a knee occurs in the medium strain amplitude region of these curves. Moreover between annealing temperatures from 360°C to 480°C the strain dependent damping becomes a maximum, i.e. a peak in the ADIF curves occurs. Other ADIF curves of quenched and fatigued material show characteristic peaks that can be attributed to individual single cracks. It is shown that all these effects are due to the formation, opening and compression of cracks present in the sample or created by thermally exerted stresses.

Amplitude Dependent Internal Friction of Magnesium Alloy AZ31 at Room Temperature

The aim of this work is to study the Amplitude Dependent Internal Friction (ADIF) of magnesium alloy AZ31 at room temperature at the frequency 20kHz. The internal friction of AZ31 at room temperature is mostly influenced by mechanical cycling at strain amplitudes in the microplastic deformation region. An excited state of the AZ31 alloy, which can be associated with a higher internal friction and lower dynamic modulus than usual state, was found immediately after mechanical cycling. When the strain amplitude drops, the diffusion of solute atoms restores the Zener atmosphere and the internal friction relaxes exponentially with the second root of time. The measurement methodology and obtained results are presented.

Interaction Potential between a Dislocation and a Pinning Atom in FCC Metals

Amplitude dependent internal friction (ADIF) was measured on 4N and 6N Cu crystals at 4K–40 K to study the interaction between a dislocation and a pinning atom. The temperature dependence of the stress amplitude necessary to produce a constant ADIF was well explained by assuming the Cottrell type interaction potential based on linear elasticity. This is clearly different from the case of Al crystals where it was necessary to consider a modified Cottrell potential including a deviation from linear elasticity near the dislocation center.

Damping behavior of Ti50.1Ni49.9 alloy in reverse martensitic transformation region

Damping behavior of Ti50.1Ni49.9 shape memory alloy during reverse martensitic transformation has been investigated by dynamic mechanical analyzer in a dual-cantilever mode. With the increase of strain amplitude, internal friction (IF) of the alloy increases in martensite and austenite states while decreases in transformation region. Based on the regularity of IF attenuation in isothermal condition, IFTr and (IFPT+ IFI) are decomposed from the strain amplitude dependent IF in transformation region. For practical application of shape memory alloys as a damping material, it is significant to evaluate the damping capacity by eliminating the influence of IFTr and consider its time independent real IF (IFPT+ IFI).

Internal friction, dilatometric and calorimetric study of anelasticity in Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga alloys

This paper investigates the structural transitions associated with different cooling rates from a high temperature disordered state and the effect of substitution of Ga atoms by Al atoms in Fe–Ga binary alloys on the ordering processes. Two iron-based low carbon (about 0.04 at.% C) alloys Fe–13 at.% Ga and Fe–8 at.% Al–3 at.% Ga are studied. Internal friction, dilatometric and calorimetric tests are carried out to check ordering in these alloys and contribution of structural defects to relaxation spectrum. Several thermally activated internal friction peaks have been observed and their activation parameters evaluated by means of temperature and frequency dependent internal friction tests using forced vibration. For most of these peaks physical mechanisms are proposed. Apart from these thermally activated relaxation peaks, a structural, frequency independent relaxation takes place at 250–300 °C. Dilatometric and DSC curves show the appearance of a contraction effect in the same temperature range. This effect was studied in alloys cooled down with different cooling rates. We believe that the frequency independent internal friction peak (denoted as the P3 peak in this paper) and peaks at dilatometric and DSC curves are controlled by the same structural mechanism and therefore the activation energy for this anelastic mechanism is derived from DSC data.

Thermally Activated Relaxation and Hysteretic Internal Friction in Ultrafine Grained Copper

Temperature and amplitude dependent internal friction (TDIF and ADIF) in ultrafine-grained copper (99.95% Cu) specimens processed by equal channel angular extrusion by route BC in 1, 4, and 8 passes and then subjected to annealing is investigated by means of dynamical mechanical analyzer DMA Q800 in the temperature range from -100 to 550 °C, amplitude range from 10-6 to 10-3, and frequency range from 0.05 to 100 Hz. Two IF peaks were registered and explained by structural relaxation due to the recrystallisation process and by thermally activated grain boundary relaxation with broad distribution of relaxation times. Increase in amplitude dependent damping in ultrafine-grained copper is due to dislocation but not grain boundary contribution.

Mechanisms of anelasticity in Fe–13Ga alloy

Thermally activated frequency and temperature dependent anelastic effects in Fe–Ga alloys are practically not studied as yet in spite of the capacity of these alloys to dissipate energy of mechanical vibrations due to magneto-mechanical damping. In this paper we have studied iron-based composition with 13 at.% Ga. Several thermally activated peaks have been discovered and their activation parameters are evaluated by means of temperature and frequency dependent internal friction tests using free-decay and forced vibrations. Physical mechanisms are proposed for most of these peaks. In addition to thermally activated relaxation peaks, an irreversible internal friction peak is recorded due to structural transformation around 200 °C. This peak is frequency independent and is accompanied by inverted modulus behaviour. High damping capacity of Fe–13Ga alloy is confirmed.

Mechanical Spectroscopy of Ultrafine Grained Copper

Temperature and amplitude dependent internal friction (TDIF and ADIF) in ultrafine-grained copper (99.95% Cu) processed by 1, 4, or 8 passes of equal channel angular pressing (route BC) and then subjected to annealing was investigated by means of mechanical spectroscopy. A dynamical mechanical analyzer DMA Q800 was used. The tests covered the temperature range from -100 to 550 °C, the strain amplitude range from 10-6 to 10-3, and the frequency range from 0.05 to 100 Hz. Two internal friction peaks were observed. They were explained by structural relaxation due to the recrystallisation process and by thermally activated grain boundary relaxation with a broad distribution of relaxation times. Increased amplitude dependent damping in ultrafine-grained copper is believed to be associated with a dislocation mechanism, rather than a grain boundary mechanism.