Low frequency relaxation effect observed on 2024 aluminium alloy

2000 ◽  
Vol 310 (1-2) ◽  
pp. 173-175 ◽  
Author(s):  
A Rivière ◽  
V Pelosin
Keyword(s):  
Aluminium Alloy ◽  
Low Frequency ◽  
Relaxation Effect ◽  
Frequency Relaxation

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.

Investigating the dielectric properties and low-frequency relaxation process of TlGaSe2 crystals

2017 ◽  
Vol 31 (12) ◽  
pp. 1750134 ◽  
Author(s):  
Oktay Samadov ◽  
Oktay Alakbarov ◽  
Arzu Najafov ◽  
Samir Samadov ◽  
Nizami Mehdiyev ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Relaxation Time ◽  
Constant Electric Field ◽  
Low Frequency ◽  
Constant Field ◽  
Impedance Spectra ◽  
Ionic Contribution ◽  
Frequency Relaxation ◽  
Average Relaxation Time ◽  
Diagram Analysis

The dielectric and impedance spectra of TlGaSe2 crystals have been studied at temperatures in the 100–500 K range in the alternating current (AC [Formula: see text]1 V). It has been shown that the conductivity of TlGaSe2 crystals is mainly an ionic characteristic at temperatures above 400 K. The well-defined peak at the frequency dependence of the imaginary part of impedance [Formula: see text] is observed in the 215–500 K temperature range. In a constant field, there occurs a significant decrease in electrical conductivity [Formula: see text] in due course. The ionic contribution to conductivity (76% at [Formula: see text]) has been estimated from a kinetic change in electrical conductivity [Formula: see text] under the influence of a constant electric field. The diagram analysis in a complex plane [Formula: see text] has been conducted by applying the method of an equivalent circuit of the substation. It has been determined that the average relaxation time of the electric module of the sample is [Formula: see text].

Low-Frequency Relaxation Phenomena in α-LiIO3: The Nature and Role of Defects

2002 ◽  
Vol 168 (1) ◽  
pp. 76-84 ◽  
Author(s):  
Y. Mugnier ◽  
C. Galez ◽  
J.M. Crettez ◽  
P. Bourson ◽  
C. Opagiste ◽  
...  
Keyword(s):  
Low Frequency ◽  
Relaxation Phenomena ◽  
Frequency Relaxation

Dynamics of Ferroelectric and Nematic Liquid Crystals Confined in Porous Matrices

1994 ◽  
Vol 366 ◽  
Author(s):  
Fouad M. Aliev
Keyword(s):  
Liquid Crystals ◽  
Heterogeneous Media ◽  
Volume Fraction ◽  
Low Frequency ◽  
Pore Wall ◽  
Polar Molecules ◽  
Average Pore ◽  
Surface Polarization ◽  
The Difference ◽  
Frequency Relaxation

ABSTRACTWe performed dielectric spectroscopy measurements to study dynamics of collective modes of ferroelectric (FLC) and molecular motion of nematic (NLC) liquid crystals with polar molecules confined in silica macroporous and microporous glasses with average pore sizes of 1000 Å (volume fraction of pores 40%) and 100 Å (27%) respectively. For FLC the Goldstone and the soft modes are found in macropores. The rotational viscosity associated with the soft mode is about 10 times higher in pores than in the bulk. These modes are not detected in micropores although low frequency relaxation is present. The last one probably is not connected with the nature of liquid crystal but is associated with surface polarization effects typical for two component heterogeneous media. The difference between the dynamics of orientational motion of the polar molecules of NLC in confined geometries and in the bulk is qualitatively determined by the total energy Fs of the interaction between molecules and the surface of the pore wall, which is found Fs ≈ 102erg/cm2.

Kinetics of Cavitation Bubble in Ultrasonic Degassing of Casting Aluminium Alloy

2017 ◽  
Vol 896 ◽  
pp. 175-181
Author(s):  
Miao Liu ◽  
Peng Zhai ◽  
Qiang Long ◽  
Chun Yang Wang ◽  
Bo Han Xiao
Keyword(s):  
Aluminium Alloy ◽  
Cavitation Bubble ◽  
Previous Experiment ◽  
Low Frequency ◽  
Silicon Alloy ◽  
Cavitation Bubbles ◽  
Low Frequency Vibration ◽  
Calculation Results ◽  
Coefficient Of Viscosity ◽  
Kinetics Of

Severe regassing was detected by previous experiment on degassing method for aluminium-silicon alloy by injecting argon with rotation. In order to further degas, ultrasonic degassing was adopted. To describe the cavitation bubbles’ movement, traditional Rayleigh-Plesset equation was modified. Classic Rayleigh-Plesset equation is strongly restricted by the applicable condition that the centre of the bubble is fixed. In this paper, a position-related Rayleigh-Plesset equation is proposed to describe the cavitation bubble's floating movement in aluminium-silicon alloy of 750°C with the coefficient of viscosity of 0.0012. As the calculation results, a bubble stimulated by high-low-frequency vibration can float up faster with violent vibration.

Effects of Low Frequency Electromagnetic Field on Segregation Layer during Hot-Top Casting of Aluminium Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 3795-3798
Author(s):  
Xiang Jie Wang ◽  
Jian Zhong Cui ◽  
Hai Tao Zhang ◽  
Hui Xue Jiang ◽  
Gao Song Wang
Keyword(s):  
Electromagnetic Field ◽  
Aluminium Alloy ◽  
Surface Segregation ◽  
Low Frequency ◽  
Casting Process ◽  
Direct Chill ◽  
Direct Chill Casting ◽  
Chill Casting ◽  
Direct Chill Casting Process

Surface segregation layer are frequently encountered during aluminium alloy direct chill casting process, and the removal of the surface segregation layer before further processing of the ingot decreases the ingot yield. In this work, the low frequency electromagnetic field was applied to study the effects of low frequency electromagnetic field on segregation layer during the direct chill casting process. The results show that under the effect of the low frequency electromagnetic field, the surface quality of ingot is improved, the structure of the ingot is refined, and the thickness of segregation layer is decreased.

Low-frequency relaxation modes and structural disorder inKTa1−xNbxO3

1990 ◽  
Vol 41 (4) ◽  
pp. 2398-2408 ◽  
Author(s):  
J. P. Sokoloff ◽  
L. L. Chase ◽  
L. A. Boatner
Keyword(s):  
Low Frequency ◽  
Structural Disorder ◽  
Relaxation Modes ◽  
Frequency Relaxation
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