Study on Cu48Zr43Al9 and Cu54Zr40Al6 Amorphous Matrix Alloys by Mechanical Spectroscopy

Anelastic properties of Bulk Metallic Glasses (BMG) were studied by mechanical spectroscopy using a flexural vibration apparatus. BMG’s samples, with nominal composition Cu48Zr43Al9and Cu54Zr40Al6, were produced by skull push-pull casting technique in rectangular cavity cooper mold. In both samples, the differential scanning calorimeter patterns have evidenced the presence of amorphous structure, although the X-ray diffraction for Cu48Zr43Al9composition has shown a heterogeneous microstructure embedded in the amorphous matrix. Anelastic relaxation spectra were obtained using an acoustic elastometer system with vibration frequency in the kilohertz bandwidth, a heating rate of 1 K/min, vacuum greater than 10-5mBar in the temperature range of 300 K to 620 K. In the flexural apparatus, an acoustic elastometer system, the internal friction (energy loss) and the elastic modulus were obtained by free decay of vibrations and by the squared of the oscilation frequency, respectively. Internal friction spectra were not reproducible among the measurements, which may imply atomic rearrangement in the samples due to consecutive heating. Normalized elastic modulus data showed distinct behavior from the first to the other measurements evidencing irreversible microstructural alterations in the samples possibly associated with mechanical relaxation due to the motion of atoms or clusters in the glassy state.

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Mechanical Spectroscopy Study on Cu53.5Zr42Al4.5 Alloy

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.312-315.1233 ◽

2011 ◽

Vol 312-315 ◽

pp. 1233-1237

Author(s):

Odila Florêncio ◽

Paulo Sergio Silva ◽

Fernando Henrique De Sá ◽

Paulo Wilmar Barbosa Marques ◽

Javier Andres Muñoz Chaves ◽

...

Keyword(s):

Internal Friction ◽

Amorphous Structure ◽

Nominal Composition ◽

X Ray Diffraction ◽

Mechanical Spectroscopy ◽

Temperature Function ◽

X Ray ◽

Casting Technique ◽

Dsc Curves

This study consists of the characterization of the anelastic properties of a Bulk Metallic Glasses (BMG) by mechanical spectroscopy, which can be defined as an energy absorption technique. The equipment used was the acoustic elastometer system, the anelastic relaxation spectra were carried out with a heating rate of 1 K/min and vacuum better than 10-5 torr, in the temperature range of 300 K to 640 K. The amorphous sample studied, with nominal composition of Cu53.5Zr42Al4.5, was processed by skull push-pull casting technique in a rectangular cavity cooper mould. Differential scanning calorimeter (DSC) curves have evidenced the amorphous structure although the X-ray diffraction (XDR) pattern has indicated a heterogeneous microstructure with amorphous matrix and some metaestable nanocrystalline phases which have not been identified yet. The dynamical elastic modulus of this alloy (between 54 GPa and 58 GPa at room temperature) and internal friction patterns as temperature function implied an increase of the crystalline phase during the measurements. This effect was confirmed with new X-ray diffraction measurements after the internal friction experiments.

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High-Temperature Mechanical Relaxation due to Dislocation Motion inside Dislocation Networks

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.137.21 ◽

2008 ◽

Vol 137 ◽

pp. 21-28 ◽

Cited By ~ 7

Author(s):

Andre Rivière ◽

Michel Gerland ◽

Veronique Pelosin

Keyword(s):

Internal Friction ◽

Relaxation Effect ◽

Dislocation Motion ◽

Relaxation Peak ◽

Mechanical Relaxation ◽

In Situ Tem ◽

Mechanical Spectroscopy ◽

Internal Friction Peak ◽

First Case ◽

Dislocation Walls

Internal friction peaks observed in single or polycrystals are clearly due to a dislocation relaxation mechanism. Because a sample observed by transmission electron microscopy (TEM) often exhibits in the same time various dislocation microstructures (isolated dislocations, dislocation walls, etc.) it is very difficult to connect the observed relaxation peak with a particular dislocation microstructure. Using isothermal mechanical spectroscopy (IMS), it is easier to compare, for instance, the evolution of a relaxation peak with measurement temperature to the microstructural evolution observed by in-situ TEM at the same temperatures. IMS was used to study a relaxation peak in a 5N aluminium single crystal firstly 1% cold worked and then annealed at various temperatures. TEM experiments performed in the same material at various temperatures equal to the temperatures used for the damping experiments made possible to link this internal friction peak with a relaxation effect occurring inside dislocation walls. In two other experiments in a 4N aluminium polycrystal and in a metal matrix composite with SiC whiskers, it is shown that the observed relaxation peaks are connected to the motion of dislocations inside polygonization boundaries in the first case and in dislocation pile-ups around each whisker in the second one. Theoretical models proposed to explain such relaxation peaks due to a dislocation motion inside a dislocation wall or network are discussed.

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Effects of Precipitation Hardedning in Co-Ni-Cr Alloy on Dissipative Motion of Dislocations by Amplitude-Dependent Internal Friction Measurements / Wpływ Utwardzenia Wydzieleniowego Stopu Co-Ni-Cr Na Rozpraszający Ruch Dyslokacji Badany Przez Zależne Od Amplitudy Pomiary Tarcia Wewnętrznego

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0493 ◽

2015 ◽

Vol 60 (4) ◽

pp. 3077-3082 ◽

Cited By ~ 2

Author(s):

R. Cosimati ◽

Daniele Mari

Keyword(s):

Elastic Modulus ◽

Internal Friction ◽

Thermoelectric Power ◽

Phenomenological Model ◽

Precipitation Hardening ◽

Thermal Cycles ◽

Mechanical Spectroscopy ◽

Threshold Strain ◽

Hardness Increase ◽

Friction Measurements

The effects of precipitation hardening occurring in a Co-Ni-Cr alloy after annealing treatments have been studied by using mechanical spectroscopy. The amplitude-dependent internal friction (ADIF) due to the dissipative motion of dislocations reveals the presence of a threshold strain for weakly pinned dislocations. The change of ADIF curves and the increase of the elastic modulus after thermal cycles producing precipitates suggest that dislocations motion is hindered leading to increasing strength of the material. Precipitation is confirmed by the changes of thermoelectric power (TEP) and by hardness measurements showing a hardness increase at the same temperature as the maximum in TEP curve. The ADIF spectra as well as the interaction between dislocations and precipitates are interpreted by proposing a phenomenological model based on the Granato-Lücke theory.

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Mechanical Spectroscopy Study on the Light Soaking Effect on Hydrogenated Amorphous Silicon

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.184.416 ◽

2012 ◽

Vol 184 ◽

pp. 416-421 ◽

Cited By ~ 1

Author(s):

H. Mizubayashi ◽

I. Sakata ◽

H. Tanimoto

Keyword(s):

Internal Friction ◽

Temperature Dependence ◽

Amorphous Silicon ◽

Hydrogenated Amorphous Silicon ◽

Wide Distribution ◽

Activation Energies ◽

Mechanical Spectroscopy ◽

Induced Changes ◽

Mild Temperature ◽

Hydrogenated Amorphous

For hydrogenated amorphous silicon (a-Si:H) films deposited at temperatures between 423 K and 623 K (a-Si:H423Kand so on), the light-induced changes in the internal friction between 80 K and 400 K were studied. The internal friction is associated with H2motion in microvoid networks, and shows the mild temperature dependence between about 80 K and 300 K (Q-180-300K) and the almost linear increase above 300 K (Q-1>300K). BothQ-180-300KandQ-1>300Kdecrease with increasing the deposition temperature, and show the mild temperature dependence ina-Si:H623K. The white light soaking with 100 mW/cm2(WLS100and so on) below 300 K caused a change inQ-180-300Kand no changes inQ-1>300K, respectively, and the light-induced changes inQ-180-300Krecovered after annealing at 423 K. The wide distribution of activation energies for H2motions between microvoids indicate that most of neighboring microvoids are connected through windows, i.e., the microvoid networks are existing ina-Si:H, and the spatially loose or solid structures are responsible for the low or high activation energies for the H2motion between microvoids, respectively. Furthermore, the light-induced hydrogen evolution (LIHE) was observed for WLS200to WLS400in a vacuum between 400 and 500 K, resulting in the disappearance of the internal friction due to the H2motion in the microvoid network.

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Analysis of Microstructural Changes with Temperature of Thermally Sprayed WC-Co Coatings by Mechanical Spectroscopy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.184.313 ◽

2012 ◽

Vol 184 ◽

pp. 313-318 ◽

Cited By ~ 5

Author(s):

Daniele Mari ◽

L.M. Berger ◽

S. Stahr

Keyword(s):

Elastic Modulus ◽

Sudden Increase ◽

X Ray Diffraction ◽

Mechanical Spectroscopy ◽

Hvof Spraying ◽

Mechanical Parts ◽

Spark Erosion ◽

Temperature Scanning ◽

First Time ◽

Thermally Sprayed

Thermally sprayed hardmetal coatings can be used to improve the wear or fatigue resistance of mechanical parts. Depending on the deposition conditions, their microstructure and phase composition are out of equilibrium at different levels due to the extreme heating/cooling rates. In the present study, the changes that occur with temperature variation are monitored by mechanical spectroscopy. Requirements to specimen of mechanical spectroscopy created the need to prepare WC-17%Co coatings of 1.2 mm thickness by high velocity oxy-fuel (HVOF) spraying. The coatings, separated from the substrate by spark erosion, were tested in a forced torsion pendulum between room temperature and 1570 K at a temperature scanning rate of 1K/min. The mechanical loss spectrum shows different features. At 800 K, a maximum M1 is observed in coincidence with a sudden increase of the elastic modulus. The change of the elastic modulus is due to a densification of the material possibly related to cobalt recrystallization. A relaxation peak located at about 1100 K is typically found in WC-Co hardmetals. It is attributed to the movement of dislocations in the cobalt phase. A sharp peak is observed at 1510 K on heating and at 1410 K on cooling. Such peak is due to the reversible transition from W3Co3C at high temperature to W6Co6C at low temperature as proven by X-ray diffraction. The reversibility of such transformation was observed for the first time.

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Critical Assessment Of The Issues In The Application Of Hilbert Transform To Compute The Logarithmic Decrement

Archives of Metallurgy and Materials ◽

10.1515/amm-2015-0267 ◽

2015 ◽

Vol 60 (2) ◽

pp. 1105-1108

Author(s):

M. Majewski ◽

L.B. Magalas

Keyword(s):

Internal Friction ◽

Hilbert Transform ◽

Computing Methods ◽

Critical Assessment ◽

Logarithmic Decrement ◽

High Dispersion ◽

Mechanical Spectroscopy ◽

Transform Method ◽

Twin Method ◽

Selection Of

Abstract The parametric OMI (Optimization in Multiple Intervals), the Yoshida-Magalas (YM) and a novel Hilbert-twin (H-twin) methods are advocated for computing the logarithmic decrement in the field of internal friction and mechanical spectroscopy of solids. It is shown that dispersion in experimental points results mainly from the selection of the computing methods, the number of oscillations, and noise. It is demonstrated that conventional Hilbert transform method suffers from high dispersion in internal friction values. It is unequivocally demonstrated that the Hilbert-twin method, which yields a ‘true envelope’ for exponentially damped harmonic oscillations is superior to conventional Hilbert transform method. The ‘true envelope’ of free decaying strain signals calculated from the Hilbert-twin method yields excellent estimation of the logarithmic decrement in metals, alloys, and solids.

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