HAL Id: jpa-00214559
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Submitted on 1 Jan 1971
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ON THE TEMPERATURE DEPENDENCE OF PINNING BY IRRADIATION-INDUCED POINT
DEFECTS IN COPPER
P. Winterhager, G. Roth, R. John, K. Lücke
To cite this version:
P. Winterhager, G. Roth, R. John, K. Lücke. ON THE TEMPERATURE DEPENDENCE OF PINNING BY IRRADIATION-INDUCED POINT DEFECTS IN COPPER. Journal de Physique Colloques, 1971, 32 (C2), pp.C2-151-C2-152. �10.1051/jphyscol:1971233�. �jpa-00214559�
JOURNAL DE PHYSIQUE Colloque C2, suppldment au no 7 , tome 32, Juillet 1971, page C2-151
ON THE TEMPERATURE DEPENDENCE OF PINNING BY IRRADIATION-INDUCED POINT DEFECTS IN COPPER
by P. WINTERHAGER, G. ROTH, R. JOHN and K. LUCKE
Institud fiir Allgemeine Metallkunde und Metallphysik der Technischen Hochschule Aachen - und Van de Graaff - Labor Aachen der Kernforschungsanlage, Jiilich.
RBsumB. - Le piegeage des dislocations dans le cuivre a et6 effectue par irradiation a basse temperature ou par chauffage d'echantillons prealablement irradies a basse temperature jusqu'8 des temperatures suffisamment elevkes. Des variations posterieures de temperature n'occasionnent aucun changement du nombre de points d'ancrage comme le montrgnt des mesures du frottement interieur dans 1es domaines du kilocycle et du mkgacycle. Ce resultat est en contradiction avecle modkle de Thompson et al. qui prkvoit un equilibre thermique entre les defauts ponctuels agissant comme points d'ancrage et les dkfauts ponctuels situes aux nceuds des dislocations.
Abstract. - Dislocations in copper were pinned by irradiation at or by warming up low temperature irradiated samples to sufficiently high temperatures. At subsequent temperature changes no change of the number of dislocations pinning points had been observed by means of kilocycle et megacycle damping measurements. This is in contradiction to the model of Thompson et al. where a thermal equilibrium between point defects on the dislocation acting as pinning point and point defects in dislocation nodes is assumed.
In a recent paper [l], Thompson, Buck, Huntington and Barnes developed a model in order to interprete their damping experiments during y-irradiation in the temperature range 3330-393 OK [2]. They assumed
(i) that the point defects produced in the lattice by the irradiation can get to the dislocation lines and subsequently along the dislocations to the nodular points by means of thermally activated migration processes.
(ii) that also the reversed migration processes are possible, but that they take place with larger time constants because of the lower energy of the point defects at the dislocation and at the nodular points.
The model leads to results fitting the data of Thomp- son et al. very well.
Because of the strong temperature dependence of the time constants this model predicts the occurrence of considerable damping changes when the temperature is changed, even after the irradiation is switched off.
It is the purpose of the present paper to investigate the validity of the model of Thompson et al. by checking this prediction. For that purpose two damping experi- ments after irradiation, one in the MHz- and one in the kHz-range, were performed the results of which are shown in figure l and figure 2.
In figure 1, the curve in the left half shows the decre- ase of damping measured in the MHz-range during irra- diation at 353 OK. After having switched off the irra- diation, the damping stayed constant if the tempera- ture was kept constant. Subsequent small temperature changes led to small damping changes (full curve) which are probably due to the temperature dependence of the damping constant B in the Granato-Liicke- theory. The damping changes predicted by the model
Time (Hours) -
FIG. 1. - Dislocation damping during (0-10.5 h) and after y-irradiation (r 10.5 h) as a function of time at various tempe-
ratures.
350 400 O K
TEMPERATURE
FIG. 2. - Number of pinning points per dislocation segment as a function of temperature evaluated from kHz-measurements after electron irradiation (full line) and according to a model
(dashed line, see text).
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1971233
C2-152 P. WINTERHAGER, G. ROTH, R. JOHN A N D K. LUCKE of Thompson et al. are given by the dashed lines.
These changes are much larger than the observed ones and go in the opposite direction.
Figure'2 shows the results of an experiment in the kHz-range. A copper sample was irradiated with electrons and at 78 OK annealed at 430 OK in order to enable theirradiation induced point defects to reach the dislocations. The subsequent measured dislocation damping turned out to be nearly independent of tempe- rature. This means that also the resulting number of pinning points which is given as full line in figure 2 is nearly independent of temperature. The model of
Thompson et al., however, predicts a strong increase with increasing temperature as shown by the dashed line.
According to the model, in both experiments the time constants should be small enough to observe actually the predicted damping changes. The fact that these changes do not occur can be considered as a proof that the reversibility of the processes, which is one of the main assumptions for the above model is not fullfilled. The present authors tend to assume that the point defects are collected in clusters, which only at high temperatures can be broken up.
References
[l] THOMPSON D. O., BUCK O., HUNTINGTON H. B. and [2] THOMPSON D. O., BUCK O., BARNES R. S. and HUNTING- BARNES R. S., J. appl. phys., 1967, 38, 3057. TON H. B., J. appl. phys., 1967, 38, 3051.
INTERNAL FRICTION MEASUREMENTS IN ALUMINIUM DURING Y-RAY AND ELECTRON IRRADIATION
H. R. KAUFMANN and G. ROTH
By Measuring the damping in the kHz and MHz region on Cu, Pb and Zn during and after electron and y-ray irradiation several dislocation pinning and depinning stages have been found in these metals.
In the present work the investigations have been extended to Aluminium.
The MHz-experiments were performed with unde- formed and slightly deformed AI-single crystals of different purity and 3-MeV-y-irradiation. The tempe- rature of irradiation was varied from 80 OKto 420 OK and the dose from 125 to 6 000 pAh where
1 pAh 1. 1 X 10'' point defects/cm3 .
In none of these experiments, however, an influence of
the irradiation on the MHz absorption was observed In the kHz-experiments the effects of electron irra- diation on the internal friction and Young's modulus of polycrystalline samples under electron irradiation up to an integrated electron flux of 1 X 10" elec- trons/cm2 have been investigated. Also here no effect of the irradiation upon the damping could be observed.
The modulus, however, showed an increase which was comparable to that found in copper.
These results seem to lead to the conclusion, that also in the case of AI dislocations are pinned by irra- diation induced defects but that this pinning does not give rise to a corresponding change in internal fric- tion.
