Internal Friction Apparatus Research Articles

Anomalous temperature dependence of modulus in water-cooled beta Ti-Mo-based alloys

The internal friction (Q-1) and relative dynamic modulus (RDM) of the specimens were measured using a multifunctional internal friction apparatus during heating and cooling. DSC (Differential Scanning Calorimetry) experiments were also carried. It is shown that the anomalous temperature-dependence(ATD) of RDM occur only in water-cooled Ti-12Mo alloys with medium Mo contents, being mainly attributed to either α”→ω or α”→ɑ+β transformation during heating. The water-cooled Ti-5Mo alloy possesses α” phase, but it cannot form ωth phase when heated. The Ti-12Mo-2X(where X = 0,Nb,Sn,Fe,Al) alloys have the ATD of RDM since they contain α” and βM phases, which can be transformed into the phases with large modulus such as ɑ, β, causing the RDM to raise with increasing temperature.DSC experiments show the occurrence of the ATD of RDM is accompanied by the phase transformation.

The Influences of Third Alloying Element on the Internal Friction Behavior and the Mechanical Properties in the Water Quenched Ti-12Mo Alloys

The influences of third alloying element on the internal friction behavior and the mechanical properties in the water quenched Ti-12Mo alloys were investigated using multifunctional internal friction apparatus and mechanical testing machine, respectively. The two relaxational internal friction peaks that are named as P1 and P2 peaks were found in the water quenched Ti-12Mo alloys. Third alloying element has influences on the P1 and P2 peaks. In addition, the young modulus and yield strength are also influenced by the addition of Third alloying element.

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.

Relationship Between Bake Hardening, Snoek-Köster and Dislocation-Enhanced Snoek Peaks in Coarse Grained Low Carbon Steel

AbstractIn the present work, specimens prepared from coarse grained low carbon steel with different prestrains were baked and then, their bake hardening (BH) property and internal friction were determined. TEM was used to characterize the dislocation structure in BH treated samples. The measurements of internal friction in prestrained samples and baked samples were carried out using a multifunctional internal friction apparatus. The results indicate that, in coarse grained low carbon steel, the bake hardening properties (BH values) were negative, which were increased by increasing the prestrain from 2 to 5%, and then were decreased by increasing the prestrain from 5 to 10%. In the specimen with prestrain 5%, the BH value reached the maximum value and the height of Snoek-Köster peak was observed to be the maximum alike. With increasing the prestrain, both of the BH value and Snoek-Köster peak heights are similarly varied. It is concluded that Snoek-Köster and dislocation-enhanced Snoek peaks, caused by the interactions between interstitial solute carbon atoms and dislocations, can be used in further development of the bake hardening steels.

Microstructure and internal friction of Ni–Ti alloys absorbing hydrogen

The microstructure and internal friction of Ni–Ti alloys after hydrogen absorption have been investigated by means of optical microscopy, X-ray diffraction, differential scanning calorimetry and low frequency torsional internal friction apparatus. The results show that, after hydrogen absorption, the grains tend to be elongated, and the nucleation and growth of hydrides are mainly concentrated at the grain boundaries. In addition, a new phase ultimately identified as Ti2NiH0·5 phase forms after absorption of hydrogen. The hydrogen induced martensite promotes the emergence of a two-stage transformation. However, the growth of hydrides causes a reduction of the hydrogen induced martensite. The hydrides act as strong pinning points, resulting in a dramatic increase in the internal friction. In addition, the marked change of the internal stress, caused by the microscopic strain and the mismatching of the volumes, also improves the internal friction.

Grain Boundary Internal Friction Peak in Nanocrystalline Aluminum Studied by Continuously Changing-Temperature

The bulk nanocrystalline aluminum are fabricated by cryomilling and hot-press sintering. The internal friction (IF) and relative dynamic modulus measurements in the nanocrystalline aluminum (Al) have been made using a multifunction internal friction apparatus (MFIFA) at low frequencies (0.2-3.0 Hz) over the wide temperature ranges from room temperature to 450 °C, while continuously changing-temperature forced vibration measurement. In the temperature spectrums of IF during heating process and cooling process, a distinct IF peak is found. Corresponding to the IF peak, the relative dynamic modulus decreases rapidly. The peak temperature of the IF peak shifts towards higher temperature with increasing frequency, i.e., the IF peak seem due to the thermal activated relaxation process. The IF peak is a grain boundary IF peak, which is associated with the diffusive grain boundary of Al/Al. Its activation energy has been calculated to be 2.21±0.04×10-19 J and the pre-exponential factor is 10-14 s in IF measurements.

Measuring of Low Frequency Internal Friction in Solids

The principles and apparatus of measuring low frequency internal friction are described in this paper. The low frequency internal friction apparatus have been evidently improved in automation and functions since the Ke,s pendulum was invented in 1947. The degree of automation of the internal friction apparatus is elevated and the functions of the apparatus are increased/ strengthened. The resolution of internal friction is increased. The accuracy of strain and frequency is also enhanced. The scope of measuring parameters such as temperature, strain, frequency and so on is enlarged.

Interstitial Solution Carbon Concentration and Defects of Ti + Nb ULC-BH Steel by Internal Friction and Positron Annihilation Methods

The interstitial solution carbon concentration and defects in continuously annealed Ti+Nb bearing ULC-BH (ultra-low carbon bake hardening) steel samples are investigated by multi-functional internal friction apparatus, positron annihilation lifetime spectroscopy (PALS) and coincidence Doppler broadening spectroscopy (CDBS). The relationship of internal friction peaks, interstitial solution carbon concentrations and movable dislocations in the samples under different conditions is analyzed. A correlation of lifetime component τ1 values with interstitial solution carbon concentrations in the samples for different continuous annealing processes is established, while a correlation of lifetime component τ2 values with multi-vacancies, vacancy clusters, microvoids and other types of defects for various continuous annealing processes is also demonstrated. Furthermore, the average lifetime results illustrate the overall defect densities for various continuous annealing processes. The CDBS analysis reflects the chemical surroundings of the defects at the annihilation sites and reveals that the peak heights of the ratio curves relate to the total number of defects such as interstitial carbon atoms, dislocations, vacancies and other types of defects. The results show that internal friction, PALS and CDBS are effective techniques to identify and characterize the interstitial solution carbon concentration, multi-vacancies, vacancy clusters, microvoids and other types of microscopic defects in annealed Ti+Nb bearing ULC-BH steel.

High Temperature Phase Transformation in a Cold-Rolled Fe-Mn-Si Alloy

The internal friction of a cold-rolled Fe-Mn-Si alloy has been investigated using a multifunctional internal friction apparatus though forced vibration method from room temperature to 950 °C. It has been shown that an internal friction peak is found on the IF-T curves during first heating at around 640 °C for the cold-rolled Fe-Mn-Si alloy. The internal friction peak is confirmed to be crystallizing peak of amorphous. The amorphous is resulted from the cold-rolling of the Fe-Mn-Si alloy.

Fabrication and internal friction behaviors of novel porous CuAlMn shape memory alloy filled with polystyrene

Polystyrene layer with adjustable thickness was introduced into a porous CuAlMn shape memory alloy, and the internal friction behaviors of the resultant materials were investigated using a multifunctional internal friction apparatus through the method of forced vibration. Two relaxational internal friction peaks accompanied by a sharp decrease of the relative dynamic modulus were found at around 95°C and 119°C, respectively. The two internal friction peaks have been ascribed to the relaxation process in a thermal equilibrium state of the polystyrene over its glass transition temperature. The damping capacity of the resultant materials was greatly elevated due to the superposition of several individual damping sources in them.

Microstructures and Damping Properties in Ni-Al-Based Alloys

The binary Ni-rich Ni64Al36 (nominal compositions, all compositions are in atomic percent unless otherwise stated,) alloy and ternary Ni-21.2 Al-20 Fe alloy ingot were prepared by melting commercial pure Ni and pure Al in a vacuum arc furnace under an argon atmosphere. The ingots were then hot rolled into a rectangle with the length of 55 mm. The microstructures of Ni-Al-based alloys were investigated using optical microscope and X-ray diffraction. The damping capacity of oil-quenched ternary Ni-21.2 Al-20 Fe alloy from different temperature is investigated using a multifunctional internal friction apparatus.

Fabrication and Damping Properties of Porous Cu

The porous Cu specimens were prepared using infiltration process. Its damping behavior was investigated using multifunction internal friction apparatus over the temperature range from 40°C to 500°C.The size of macroscopic pore is in the order of a millimeter (1.0mm) and in large proportions, typically up to 60vol%. The measured IF (internal friction) shows that the damping capacity of porous Cu is higher than that of its bulk metal. It’s found that two IF peaks present at the internal friction against temperature curves at around 280°C and 400°C.The high-temperature arises from the relaxation of grain boundaries. The low-temperature peak may origin from the interaction of dislocation and grain boundaries. TEM observations showed the dislocation substructures exist in the porous Cu. Based on the observed experimental phenomena, a four-parameter mechanical model was used for describing the operative damping mechanism of the low-temperature peak in the porous Cu specimen.

Effects of Macroscopic Pores on the Damping Behavior of Zn-Al Eutectoid Alloy

The objective of present work is to investigate the effect of macroscopic pores on the damping behavior of Zn-Al eutectoid alloy. The damping behavior of the foamed Zn-Al (FZA) eutectoid alloy prepared by air pressure infiltration process with macroscopic pores is characterized by internal friction (IF). Macroscopic pores size are on the order of a millimetre (0.51.0mm). The IF was measured on a multifunction internal friction apparatus (MFIFA) at frequencies of 0.5, 1.0 and 3.0 Hz over the temperature range of 25 to 400°C, while continuously heating temperature. The damping capacity of the FZA eutectoid alloy, with two different porosity and sizes of macroscopic pores, were compared with that of bulk Zn-Al eutectoid alloy specimen. The damping capacity of the materials is shown to increase with introducing macroscopic pores. Finally, the operative damping mechanisms in the FZA eutectoid alloy were discussed in light of IF measurements.

Low-Frequency Damping Behavior of Porous Magnesium

The well-distributed porous magnesium was prepared through powder metallurgy route basing on space-holding method. The damping behavior of the porous magnesium was characterized by internal friction and measured by a multi-function internal friction apparatus. Experimental results revealed that the damping capacity of the porous magnesium was increased compared to that of the bulk magnesium, which can be understood by a dislocation damping mechanism associated with an inhomogeneous stress and strain distribution around the pores. In addition, an internal friction peak was observed in the spectra of internal friction against temperature. It was suggested that the dislocation sliding arising from a thermal activation process should be responsible for the peak appearance.

Grain Boundary Relaxation in a Fe-Cr-Al Alloy

The features of grain boundary relaxation of a (wt.%)Fe-25Cr-5Al alloy have been investigated using a multifunction internal friction apparatus. The grain boundary relaxation peak appears at about 630oC on the internal friction-temperature curves for the alloy. The peak temperature shifts toward high temperature with increasing frequency. In terms of Arrihenius relation, the activation energy is calculated to be 4.07(±0.15)eV and the pre-exponential factor is 6.2×10-24±1s. Grain boundary relaxation strength remarkably decreases with increasing grain size. When grain size reaches 520μm, the grain boundary relaxation peak almost disappears.

Internal fraction of polymer composites with nanosilicas fabricated by ultraviolet irradiation

The internal friction behavior of the nanocomposite polymer was studied using a multifunction internal friction apparatus. It is shown that the internal friction peak in the polymer has a relaxation feature and the peak height is almost independent of frequency for the polymer without nanosilica. Nevertheless, the peak height for the polymer with nanosilica increases not only with increasing vibration frequency, but also with increasing nanosilica content, which results from the stronger interaction between nanosilica with polymer chains. For the nanocomposite polymer with 3 wt% nanosilica, the activation energy of polymer chain motion is bigger than that of neat copolymers.

Internal Friction of Polymer Composites with Nanosilicas Fabricated by Ultraviolet Irradiation

The internal friction behavior of the nanocomposite polymer was studied using a multifunction internal friction apparatus. It is shown that the internal friction peak in the polymer has relaxation feature and the peak height is almost independent of frequency for the polymer without nanosilica. Nevertheless, the peak height in the polymer with nanosilica increases not only with increasing vibration frequency, but also with increasing nanosilica content, which results from the stronger interaction between nanosilica with polymer chains. For the nanocomposite polymer with 3 wt.% nanosilica, the activation energy of polymer chain motion is higher than that of neat copolymers.

Effects of Macroscopic Pores on the Damping Behaviors of Metal Materials

A large number of macroscopic pores were introduced into commercially pure aluminum (Al) and Zn-Al eutectoid alloy by air pressure infiltration process to comparatively study the influence of macroscopic pores on the damping behaviors of the materials. Macroscopic pores size are on the order of a millimetre (0.5~1.4mm) and in large proportions, typically high 76vol.%. The damping behavior of the materials is characterized by internal friction (IF). The IF was measured on a multifunction internal friction apparatus (MFIFA) at frequencies of 0.5, 1.0 and 3.0 Hz over the temperature range of 25 to 400 °C, while continuously changing temperature. The damping capacity of the metal materials is shown to increase with introducing macroscopic pores. Finally, the operative damping mechanisms in the metal materials with macroscopic pores were discussed in light of IF measurements.

Phase transformation in oil-quenched Ni–21.2Al–20Fe alloy

The internal friction ( Q −1) and the relative dynamic modulus (RDM) of the oil-quenched Ni–21.2Al–20Fe alloy were measured using a multifunctional internal friction apparatus by forced-vibration methods from room temperature to 200 °C. An internal friction peak is represented on the internal friction-temperature curve at about 113 °C during heating and the peak is shifted to about 38 °C during cooling for the oil-quenched alloy. The peak temperature does not change for different vibration frequencies during both heating and cooling, and therefore the peak is non-relaxational. It has been shown that the peak-heights decrease with increasing f and decreasing heating rate ( T ˙ ) and are linearly and directly proportional to T ˙ / f . DSC measurements show that there is an endothermal peak at 107 °C and an exothermal peak at 42 °C on the heating curve and cooling curve, respectively. Both temperature values are similar to those of the internal friction measurements during heating and cooling, respectively. XRD results show that the oil-quenched Ni–21.2Al–20Fe alloy possesses martensitic structures (L1 0) in addition to Ni 3Al and Ni 5Al 3. It can be deduced that the internal friction peak during heating is resulted from reverse martensitic transformation of L1 0 → γ and originated from martensitic transformation of γ → L1 0 during subsequent cooling. The internal friction peak height increases when Fe content is raised.

Anelastic Behavior of Nanocrystalline Fe-Cr Alloy Obtained by Mechanical Alloying

Anelastic behavior of nanocrystalline Fe-17 wt.%Cr alloy obtained by mechanical alloying was investigated using a multifunctional internal friction apparatus. Internal friction (Q-1) and relative dynamic modulus (f2) have been measured as a function of temperature by free-decay method from room temperature to 400oC for the ball-milled Fe-17 wt.%Cr alloy The specimens with different milling time were examined by XRD to determine the solid solubility of Fe and Cr atoms and detect the lattice strain of the compacted specimen before and after annealing. TEM observation was employed to obtain further information about the morphology and microstructure, especially crystalline size, of the milled Fe and Cr mixture powders. It has been suggested that the anelastic behavior of ball-milled nanocrystalline Fe-17 wt.%Cr alloy origins from the viscoelastic sliding at the interfaces resulting from the thermally-activating process. The damping increasing of the specimen with smaller grain sizes is larger than that of the specimen with larger grain sizes with increasing temperature since the former contains more interfaces. The increase in the relative dynamic modulus is attributed to the structural reordering with the lowering of lattice micro-strain that is produced during milling when temperature is over 300oC.