DISLOCATION MOTION IN VA METALS STUDIED BY INTERNAL FRICTION

1981 ◽  
Vol 42 (C5) ◽  
pp. C5-67-C5-72
Author(s):  
S. Okuda ◽  
H. Mizubayashi ◽  
N. Kuramochi ◽  
S. Amano ◽  
M. Shimada ◽  
...  
Keyword(s):  
Internal Friction ◽  
Dislocation Motion

EVIDENCE OF NONLINEAR DISLOCATION MOTION IN INTERNAL FRICTION EXPERIMENTS

1987 ◽  
Vol 48 (C8) ◽  
pp. C8-113-C8-117
Author(s):  
H.-J. KAUFMANN ◽  
P. P. PAL-VAL ◽  
V. M. CHERNOV ◽  
D. A. KAMAJEV
Keyword(s):  
Internal Friction ◽  
Dislocation Motion

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

2008 ◽  
Vol 137 ◽  
pp. 21-28 ◽  
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.

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

2012 ◽  
Vol 184 ◽  
pp. 245-250
Author(s):  
Yasuhiro Aruga ◽  
Yoshiki Morikawa ◽  
Satoshi Tamaoka ◽  
Yoichi Nishino
Keyword(s):  
Stress Relaxation ◽  
Plastic Strain ◽  
Internal Friction ◽  
Strain Amplitude ◽  
Annealing Time ◽  
Three Dimensional ◽  
Atom Probe ◽  
Dislocation Motion ◽  
Amplitude Dependence ◽  
Stress Relaxation Behavior

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.

Internal Friction Study of Vacancy Hardening in B2 Fe Al Alloys

2012 ◽  
Vol 184 ◽  
pp. 81-86 ◽  
Author(s):  
Yoichi Nishino ◽  
Kazuya Ogawa ◽  
H. Tanaka
Keyword(s):  
Plastic Strain ◽  
Internal Friction ◽  
Strain Amplitude ◽  
Peak Height ◽  
Dislocation Motion ◽  
Al Alloys ◽  
Anomalous Increase ◽  
Internal Friction Peak ◽  
Quenching Temperature ◽  
Friction Study

nternal friction behaviour of B2 FeAl alloys has been examined to reveal the correlation of the microplasticity and thermal vacancies. The internal friction peak for Fe60Al40 appears at around 550 K, and the peak height increases with increasing quenching temperature. The curves of internal friction against the strain amplitude shift to larger strain amplitude as the quenching temperature increases. Analysis of the amplitude-dependent internal friction provides 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 the plastic strain of 1×10-9 increases linearly with the square root of the net peak height. Remarkably, the microflow stress decreases with rising temperature but turns to increase above 500 K when measured after holding for 1 h at test temperatures. The anomalous increase in the microflow stress is caused by the creation of thermal vacancies at intermediate temperatures.

Internal Friction in Plastically Deformed High-Purity NiAl Single Crystals

1998 ◽  
Vol 552 ◽  
Author(s):  
M. Hirscher ◽  
D. Schaible
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
High Purity ◽  
Formation Enthalpy ◽  
Dislocation Motion ◽  
Zone Melting ◽  
Interstitial Impurity ◽  
Impurity Atoms ◽  
Kink Pair ◽  
Friction Measurements

ABSTRACTHigh-purity stoichiometric NiAl single crystals have been prepared by crucible-free inductive zone melting and afterwards well annealed at temperatures below 1200 K. Internal friction measurements of torsionally deformed single crystals show two relaxation maxima at 500 and 800 K which anneal during the measurement. The first maximum can be assigned to the dislocation motion by kinkpair formation and the annealing to pinning of these dislocations by interstitial impurity atoms. The second maximum is attributed to the Snoek-Köster relaxation of dislocations in the presence of mobile interstitial impurity atoms and the annealing to the pinning of dislocations by vacancies. The kink-pair formation enthalpy in NiAl was estimated.

Thermally Activated Dislocation Motion Studied by Internal Friction

2002 ◽  
Vol 203-205 ◽  
pp. 249-252 ◽  
Author(s):  
Zuzanka Trojanová ◽  
Pavel Lukáč ◽  
Werner Riehemann
Keyword(s):  
Internal Friction ◽  
Dislocation Motion ◽  
Thermally Activated

Investigation of Defect Dynamics in Al-Si-Mg Polycrystals by Simultaneous Measurements of Internal Friction and Acoustoplastic Effect

2012 ◽  
Vol 184 ◽  
pp. 155-160
Author(s):  
K. Sapozhnikov ◽  
S. Golyandin ◽  
Sergey Kustov
Keyword(s):  
Internal Friction ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Heat Treatments ◽  
Mg Alloys ◽  
Structural Defects ◽  
Natural Ageing ◽  
Simultaneous Measurements ◽  
Combined Action

Dynamics of structural defects was investigatedin situduring quasistatic deformation of polycrystalline Al-1wt.%Si-0.3wt.%Mg and Al-12wt.%Si-0.3wt.%Mg alloys by means of simultaneous measurements of internal friction and acoustoplastic effect. The alloys were subjected to different heat treatments after quenching: natural ageing at room temperature (T4 treatment) and peak ageing at 433 K for 8 hrs (T6 treatment). This enabled us to study the effect of different microstructure components – solute clusters (for the T4 treatment), GP zones and β (( precipitates (for the T6 treatment), coarse Si particles (for Al-12wt.%Si-0.3wt.%Mg) – on the irreversible and reversible components of dislocation motion under the combined action of oscillatory and quasistatic stress. Based on the data obtained, conclusions have been drawn about microstructural mechanisms of the acoustoplastic effect.

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