Mechanical Spectroscopy of Nanocrystalline Metals

2000 ◽  
Vol 634 ◽  
Author(s):  
E. Bonetti ◽  
L. Pasquini ◽  
L. Savini
Keyword(s):  
Mechanical Behavior ◽  
Low Frequency ◽  
Creep Recovery ◽  
Mechanical Spectroscopy ◽  
Gas Condensation ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Mechanical Attrition ◽  
Nanocrystalline Iron ◽  
Disorder Degree

ABSTRACTThe mechanical behavior of nanocrystalline iron and nickel prepared by mechanical attrition and inert gas condensation was investigated using mechanical spectroscopy techniques in the quasi static-and low frequency dynamic stress-strain regimes. The measures were performed on samples previously stabilized by thermal annealing at low homologous temperatures. The results of elastic energy dissipation, creep, and creep recovery measurements performed in the low strain regime (ε = 10−5−10−3) allowed to trace a phenomenological picture of the anelastic and viscoplastic behavior of nanocrystalline Ni and Fe in the 300-450 K range with different grain sizes and interfaces disorder degree. Activation energies of the thermally activated anelastic and plastic mechanisms responsible for the mechanical behavior have been evaluated.

Low Frequency Relaxation Effect Observed in Al-Mg Alloy

2012 ◽  
Vol 184 ◽  
pp. 149-154 ◽  
Author(s):  
N. Benyahia ◽  
Michel Gerland ◽  
C. Belamri ◽  
Andre Rivière
Keyword(s):  
Low Frequency ◽  
Relaxation Effect ◽  
Solution Temperature ◽  
Transient Effects ◽  
Mechanical Spectroscopy ◽  
Slow Cooling ◽  
Thermally Activated ◽  
Measurement Experiment ◽  
Frequency Relaxation ◽  
Large Frequency

Al-12 wt% Mg alloys have been studied by isothermal mechanical spectroscopy. The samples were quenched then annealed at various temperatures. Experiments were performed in a very large frequency range (10-4Hz – 50 Hz) between room and solidus temperatures. For each temperature of measurement, experiment started after complete microstructure stabilization of the sample and therefore the transient effects due for instance to β (( and β′ precipitation were not observed. Nevertheless, a new relaxation effect was obtained in the reversion temperature range. This effect is not thermally activated. It is maximal at about 0.1 Hz and increases with the temperature of measurement. It completely disappears after annealing at solid solution temperature and successive slow cooling and therefore is linked to the β precipitates. This effect is interpreted as a phase transformation at the precipitate surface induced by the applied stress.

Eutectoid Al-51at%Zn Alloy Studied by Isothermal Mechanical Spectroscopy

2012 ◽  
Vol 184 ◽  
pp. 167-172 ◽  
Author(s):  
Andre Rivière ◽  
Veronique Pelosin ◽  
Michel Gerland
Keyword(s):  
Transition Temperature ◽  
Low Frequency ◽  
Mechanical Spectroscopy ◽  
Thermally Induced ◽  
Atom Diffusion ◽  
Thermally Activated ◽  
Relaxation Parameters ◽  
Zn Alloy ◽  
Large Frequency ◽  
Internal Friction Spectra

sothermal mechanical spectroscopy measurements were performed in an Al-51 at % Zn alloy at various temperatures below and above the eutectoid transition temperature: during a heating the α-β eutectoid mixture changes into α solid solution at 550 K. Damping experiments were performed in a very large frequency range (10-5– 50 Hz) between room temperature and 673 K. Internal friction spectra performed between 200 K and 540 K, exhibit two thermally activated relaxation peaks (P1 and P2). P1 decreases and disappears with the increase of measurement temperature while P2 appears and increases. P2 totally disappears above the eutectoid transition temperature. Above 550 K, a new peak (P3) is evidenced at very low frequency. The relaxation parameters of P3 (limit relaxation time τ0= 9×10-7and activation energy H = 105 kJ/mole (1.1 eV)) allow to associate this peak with the motion of sub grain boundaries. P1 and P2 (τ0≈ 10-7and H ≈ 70 kJ/mole (0.75 eV) for both peaks) are associated with a thermally induced atom diffusion across the α-β interface.

Low Frequency Mechanical Spectroscopy of High Damping Mg-3wt.%Ni Alloy

2010 ◽  
Vol 146-147 ◽  
pp. 1761-1764
Author(s):  
Di Qing Wan ◽  
Ya Juan Liu
Keyword(s):  
Grain Boundary ◽  
Low Frequency ◽  
Mechanical Analysis ◽  
Mechanical Spectroscopy ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Ni Alloy ◽  
Dislocation Movement ◽  
Boundary Relaxation ◽  
Two Peaks

The Dynamic Mechanical Analysis (DMA) was applied to investigate the low frequency mechanical spectroscopy response of as-cast high damping Mg-3wt.%Ni hypoeutectic alloys. There are two peaks appearing on the temperature dependent damping spectrum (-100 - 420 °C). The broad peak P1 is overlapped by some small peaks due to the thermally activated dislocation movement, while the P2 peak is a solute grain boundary relaxation peak.

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

Effects of residual thermal stress on mechanical behavior of cermets with different grain sizes

2021 ◽  
pp. 117428
Author(s):  
Jinghong Chen ◽  
Chong Zhao ◽  
Hao Lu ◽  
Yanan Li ◽  
Xuemei Liu ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Mechanical Behavior ◽  
Residual Thermal Stress ◽  
Grain Sizes

Toward High-Resolution Mechanical Spectroscopy HRMS - Logarithmic Decrement

2012 ◽  
Vol 184 ◽  
pp. 467-472 ◽  
Author(s):  
Leszek B. Magalas ◽  
M. Majewski
Keyword(s):  
High Resolution ◽  
Low Frequency ◽  
Logarithmic Decrement ◽  
Frequency Resolution ◽  
Mechanical Spectroscopy ◽  
Spectral Leakage ◽  
Experimental Noise ◽  
Relative Errors ◽  
The Way

In this work, we present the comparison between different methods used to compute the logarithmic decrement,δ. The parametric OMI method and interpolated DFT (IpDFT) methods are used to compute theδfrom free decaying oscillations embedded in an experimental noise typical for low-frequency mechanical spectrometers. The results are reported forδ= 5×10-4, = 1.12345 Hz and different sampling frequencies, = 1 kHz and 4 kHz. A new YM algorithm yields the smallest dispersion in experimental points of the logarithmic decrement and the smallest relative errors among all investigated IpDFT methods. In general, however, the IpDFT methods suffer from spectral leakage and frequency resolution. Therefore it is demonstrated that the performance of different methods to compute theδcan be listed in the following order: (1) OMI, (2) YM, (3) YMC, and (4) the Yoshida method, Y. For short free decays the order of the best performers is different: (1) OMI and (2) YMC. It is important to emphasize that IpDFT methods (including the Yoshida method, Y) are discouraged for signals that are too short. In conclusion, the best methods to compute the logarithmic decrement are the OMI and the YM. These methods will pave the way toward high-resolution mechanical spectroscopy HRMS.

Sign in / Sign up

Export Citation Format

Share Document