Data necessary to determine the activation energy and volume of the creep process in zinc have been obtained in the temperature range 1.5 to 80 °K by means of a differential technique. While calculating the activation parameters the influence of quantum phenomena on fluctuation‐induced dislocation motion over local barriers of the crystal lattice were taken into account. The analysis of the dependences of the activation parameters on temperature and effective stress shows that below a certain characteristic temperature θ, which for zinc is equal to 26 °K, the activation parameters should be calculated using quantum formulas, whereas for T > θ they may be calculated using conventional classical formulas. The obtained values of the activation parameters and their temperature dependences form a basis used to make conclusions about the nature of obstacles controlling the low‐temperature creep in Zn.

The creep of single crystals of Zn deformed by simple shear along the basis plane (0001) has been investigated in the temperature range 1.5 to 80 OK. It is shown that the influence of temperature on the creep in the investigated temperature range is weaker than that predicted by t h e classical theory of thermally activated creep. A peculiar temperature run of parameters describing the creep process has been discovered and proved anomalous as compared with the classical run. A mechanism for the influence of zero-point vibrations of the dislocation line on its motion through an aggregate of local obstacles is suggested and analyzed. The results obtained in this way show a satisfactory agreement with the experimental data. ~CCneAOBaHa IIOJI3y4eCTb MOHOKPHCTaJIJIOB Zn, He@OpMHpyeMbIX sHCTbIM CABHrOM no KTIOCXOCTH 6 a a~c a (0001) B o 6 n a c~~r TeMIlepaTyp 1.5 A0 80 O K . n O K a -3aH0, YTO B HCCJleHOBaHHOM TeMIIepaTypHOM HHTepBaJle BJIHFlHHe TeMllepaTypbI YeCKOfi TePMOaKTHBHPYeMOfi IIOn3yseCTH. 06HapyWeH aHOMaJIbHbIfi, IIO CpaB-HeHHH3 C KJIaCCMYeCKHM, TeMIIepaTypHbIfi XOR IIapaMeTpOB, OIIMCbIBaIO~HX np0-UeCC nOn3yYeCTH. UPeHJIOWeH I4 IIpOaHanH3HpOBaH MeXaHH3M BJIHHHHEI HyJIeBbIX KOJIf36aHHfi .QHCJlOKagHOHHOfi JIMHHH Ha ee HBHWeHHe sepe3 COBOKYllHOCTb JIOKaJIb-HbIX IIpeIlHTCTBtifi. ~OJlyYeHHhIe npH TaKOM PaCCMOTpeHHH pe3ynbTaTbI YAOB-JleTBOpHTeJIbHO COI' JIaCyIOTCH C 3XCIlepHMeHTaJIbHbIMII AaHHbIMM.Ha n o m y~e c~b mnHeTcn 6onee CJIafibIM, YeM n p e~c x a 3~s a e~ Teopm KaaccH-

A mechanism underlying fluctuational bending of dislocation segments is considered which is based on periodical ordering in the thermal motion of atoms near the dislocation core. Basic principles of calculating the probability of dislocation unpinning from local obstacles due to the fluctuations are formulated. As found, the interaction of dislocation segments experiencing fluctuational bending with phonons and/or conduction electrons, described in the framework of the usual dissipation model, can result in a reduction of the energy of atoms near the dislocation core during the fluctuation. Consequently, the effective activation energy of the dislocation unpinning from local obstacles is increased, i.e. the mean velocity of the activated dislocation motion drops. Activated dislocation motion a t low temperatures is analysed with an account of the possible quantum mechanical fluct,uations which can arise in condensed structures owing to the correlation of atomic zero point vibrations. An expression is derived for the probability of low temperature fluctuational dislocation with allowance for quantum mechanical effects.Ein Mechanismus, auf den sich die Biegungsflulrtuationen von Versetzungsabschnitten zuriickfiihren lassen, wird betrachtet. E r beruht auf der periodischen Anordnung der thermischen Bewegung der Atome in der Nahe des Versetzungskerns. Die Grundprinzipien fiir die Berechnung der Wahrscheinlichkeit von Versetzungsbefreiung von ortlichen Hindernissen infolge der Fluktuationen werden formuliert. Wie gefunden wird, kann die Wechselwirkung von Versetzungssegmenten, die Fluktuationskrumrnung mit Phononen iind/oder Leitungselektronen erleiden und i m Rahmen des iiblichen Dissipationsmodells beschrieben werden, zu einer Reduzierung der Energie der Atome in der Nahe des Versetzungskernes wahrend der Fluktuation fuhren. Folglich wird die effektive Aktivierungsenergie der Versetzungsbefreiung von lokalen Hindernissen erhoht, d. h. die mittlere Geschwindigkeit der aktivierten Versetzungsbewegung fiillt. Die aktivierte Versetzungsbewegung bei tiefen Temperaturen wird beziiglich der moglichen quantenmechanischen Fluktuationen, die in kondensierten Strukturen infolge der Korrelation der atomaren Nullpunktsschwingungen auftretan konnen, analysiert. Ein Ausdruck wird abgeleitet fur die Wahrscheinlichkeit von Tieftemperaturfluktuationsversetzungen unter Beruclrsichtigung quantenmechanischer Effekte. 1) Pereyaalavskaya str. 23, 310015 Kharkov, USSR. 23.

A. I. OSETSKII B>-The temperature behaviour of the fluctuation-dissipative effects is analysed. At sufficiently low temperatures it is controlled by variations in the viscosity coefficients of the phonon and electron gas. Some experimental data are quoted which can be regarded as evidence for the influence of fluctuation-dissipative effects upon the low temperature plasticity of materials, i.e. change in the activation energy during N-S transition, correlation between the activation energy and the phonon gas viscosity, etc. The temperature dependence of such values as the flow stress, activation energy and activation volume, work hardening coefficients, and the relaxation depth of effective stresses are analysed for the range of temperatures where fluctuation-dissipative effects are essential. The dependences are calculated both, in the framework of the classical approximation and in the fluctuation-dissipat,ive model, and compared with the data measured with single crystals of lead and zinc a t temperatures below the Debye point. As found, many anomalies observed at low temperatures in the temperature behaviour of the plasticity parameters can be satisfactorily explained as manifestat,ions of the impact of dissipation on the velocity of activated dislocation motion through t,he crystal.