Kinetic analysis of dynamic point defect pinning in aluminium initiated by strain rate changes

Constitutive relation based on Taylor slip analysis to replicate work-hardening evolution

“…Hasegawa and Kocks [5] recovered [1 1 1] Al crystals and the yield stress after annealing was approximately 50% of the prior flow stress, suggesting that the measured stored energy comprises only about 25% forest dislocation, with the remainder being deformation debris such as elongated loops in the cell walls [16,25] It is apparent from Fig. 7b that P = 4 will result in the recoverable energy due to point defect production being negligible, which contradicts observation [33]. Thus k is less than d C at low strains as deduced from Figs.…”

Study of vacancy-type defects by positron annihilation in ultrafine-grained aluminum severely deformed at room and cryogenic temperatures

“…In Al, g is 1 for a monovacancy and 1/6 for a divacancy, S M is set to 0.8k and 1.2k for mono-and divacancies, respectively [37], where k is the Boltzmann constant. E M for a monovacancy is in the range of 0.61-0.64 eV [29,30], while E M for a divacancy is in the range of 0.42-0.5 eV [30]. In this work we have used E M = 0.62 eV for a monovacancy and E M = 0.46 eV for a divacancy.…”

“…Therefore, divacancies are likely to be the second major type of vacancy-type defects in the sample CT-4. Divacancies in Al are more mobile than monovacancies because the activation energy for migration is lower (0.42-0.5 eV for divacancies [30] compared to 0.61-0.64 eV [30,31] for monovacancies). This indicates that some divacancies may annihilate in the grain boundaries.…”

“…The formation energy for a self-interstitial (2.59 eV) is approximately four times that for a vacancy (0.68 eV) [29], which suggests that it is hard to form self-interstitials in Al. Even if self-interstitials can be generated, they will easily annihilate in the sinks because the activation energy for migration of a self-interstitial (0.1 eV [28]) is much smaller than that for a vacancy (0.61-0.64 eV [29,30]). Therefore, it is expected that the concentration of self-interstitials is negligible and vacancy-type defects are the common point defects in Al subjected to plastic deformation.…”

“…In the sample RT-4, C D is larger than C N , indicating that bulk vacancies tend to migrate to the grain boundaries due to the low dislocation density in the NR and barriers may exist to prevent vacancies from annihilating into grain boundaries. The possible barriers sealing grain boundaries may be high-energy and nonequilibrium configurations [37] along the grain boundaries or/and nanosized precipitates in the grain boundaries [30]. The continuous migration of vacancies and the grain boundary sealing effect result in an enlarged d in the sample RT-4.…”