Nucleation and growth of interstitial dislocation loops in irradiated aluminum

Abstract

Formation and growth of dislocation loops of interstitial type in Al (99.999%) during in situ irra diation with 1 MeV electrons at 20-150°C using a high voltage electron microscope are investigated by transmission electron microscopy. Experimental results are analyzed within the classical theory and kinetic model of nucleation and growth of loops. The parameters controlling the process of radiation induced for mation of interstitial dislocation loops under irradiation are determined.Keywords: dislocation loops, nucleation and growth of loops, high voltage electron microscopy (HVEM), kinetic model of loop growth.

The possibilities to lower the stacking fault energies of aluminum materials investigated by first-principles energy calculations

“…With the rapid development of the cosmic space and nuclear industries, many devices made of aluminum alloys may serve under the condition of irradiation damage. Dislocation loops may be generated easily owing to the creation of interstitials and vacancies by the irradiation of energetic particles (such as electrons, neutrons and other high energy particles) [11][12][13]. In addition, the vacancies and interstitials may be produced in aluminum materials during quenching from high temperature to low temperature, or through a high temperature plastic deformation process [14][15][16].…”

Nucleation of interstitial dislocation loops in metals under electron irradiation

“…The rate of change in the concentration of freely migrating interstitial atoms C i is given by (7) The term 2K i in (7) describes the accumulation rate of the general concentration C i2 of interstitial atoms in dumbbell configurations with concentration C 2 : C i2 = 2C 2 . The rate of variation of C i2 is (8) From (8), we obtain (9) where K i is the reaction constant of the formation of dumbbell interstitial atoms and τ 2 is the nucleation time of these complexes. Since the diffusion mobility of interstitial atoms is very high and their dynamic concentration C i quickly saturates, one may use a qua sistationary approximation to represent (9) in a sim pler form: (10) Hence, it follows that (11) where (12) Upon further irradiation, the general concentra tion of interstitial atoms in complexes (n) increases only owing to their growth, whereas the concentration C 2 remains constant because absorption efficiency f(n) of freely migrating interstitial atoms in the complexes consisting of more than two atoms (n > 2) is greater than that for the reaction of dumbbell formation where f(n) = 1.…”

“…In [5], the authors presented kinetic dependences for the total concentration of interstitial atoms in dislocation loops under electron irradiation of alumi num in the temperature interval of 293-423 K obtained in [9]. Processing of these data was carried out using Eq.…”

“…The second term on the right hand side describes the growth process of dislocation loops. The validity of this mechanism and its parameters were repeatedly confirmed in analyzing the experiments on irradiation of V, Ti, Al, and its solid solutions Al-Zn, Al-Sc, and Al-Mg when irradiated with electrons with energies of 1 and 2.2 MeV at temperatures of 293-343 K [1][2][3][4][5][6][7][8][9]. At the same time, a correct mechanism of the dislocation loop formation which allows deter…”