The internal friction peaks α and β1 in irradiated or deformed pure iron

Abstract

on the occasion of his 75th birthdayThe internal friction spectrum of pure iron specimens, deformed at room temperature, presents near 25 K (1 Hz) a peak a attributed t o the generation of kink pairs on non-screw dislocations. When such specimens arc subsequently irradiated or plastically deformed at low temperatures, peak a is suppressed and replaced by peak PI, attributed to the interaction between non-screw dislocations and intrinsic point defects. The evolution of p1 and its final reconversion into a during successive annealing treatments yields information about the arrival, clustering, and final annihilation of defects on the dislocation segments. The interpretation of the results is consistent with the long-range migration of interstitials at 125 K and of vacancies a t 220 K.Apres deformation it temphratnre ambiante. un Bchantillon de fcr pur presente un pic CI situB vers 25 K (1 Hz) a t t r i b d B la generation de double dBcrochements sur les dislocations non vis.Quand cct Bchantillon est ensuite irradiB, ou bien deform6 plastiquement A bassc temperature. le pic a est supprime e t remplace par un pic PI, attribu6 B I'interaction entre les dislocations non vis e t des dkfaut,s ponctuels intrinshques. L'~vo1ution du pic B1 e t sa reconversion finale en un pic a a u cows de traitements thermiques successifs donne dcs informations a u sujet de I'arrivhe des defauts sur les segments de dislocations, puis de leur agglom6ration e t de leur annihilation. L'intcrpretation des rksultats est compatible avec I'hypothbse d'une migration tridiniensionnelle a longue distance des interstitiels B 125 K e t des Iacunes B 220 K. l ) 85X, 38041 Grenoble CBdex, France.

Progress and problems in the understanding of the dislocation relaxation processes in metals

“…The preceding interpretation is fully compatible with the internal-friction study (at 0.5 Hz, surface-strain amplitude 1 × 10 −6 ) of Ritchie et al [75] on iron of the same provenance as that investigated by San Juan et al [73]. The annealing behaviour of the internal friction in the temperature interval 30-50 K after 5% tensile deformation at 77 K and after 5% tensile deformation at room temperature followed by 5% tensile deformation at 77 K was found 14 Since kinks are dislocation segments, they do possess slip planes.…”

“…This may have to do with the rather low purity of their samples. Note that the designation ␤ 1 of Ritchie et al [75] has a different meaning. in high vacuum, the height of the ␤-peak was reduced by almost two powers of ten [Q −1 (␤) = 2 × 10 −5 ].…”

Mobility of Twin Boundaries in Fe-Pd-Based Ferromagnetic Shape Memory Alloys

“…In fact, damping mechanisms involving dislocations relaxation processes in iron and in bcc and fcc metals at low temperatures are developed with activation energies higher than 6.2 kJ/mol. [41][42][43][44][45][46][47][48] The lowest activation energy was reported for the kink pair formation in nonscrew dislocations in tungsten (α relaxation, 6.2 kJ/mol). 44) In addition, dislocation relaxation processes give rise to damping peaks as a function of temperature depending on the oscillating frequency, but in the present study on FSMA, relaxation peaks within the martensitic phase were not detected.…”

The study of dislocation dynamics in thermally aged Fe–1%Cu–C alloys by internal friction measurements

“…This peak has been already observed and analysed by magnetic after-effect and IF spectra of α-Fe and Fe-Cu alloys, and assigned to the relaxation process of thermally activated dislocation motion (CWD-peak). As already discussed [19], the activation energy of the CWD-peak (1.1 eV) is somewhat different from the γ -relaxation (1.07 eV) [20,24,25], which is typically observed in pure metals. These facts as well as its overall shape indicate that E 2 peak could be equivalent to the double kink- pair relaxation process, which occurs in alloys.…”