Formation of vacancy-type dislocation loops in tungsten bombarded by 60 keV Au ions

Abstract

The formation of vacancy-type dislocation loops in tungsten specimens as produced by irradiation with 60 keV Au ions is investigated by transmission electron microscopy. The majority of the loops is found to haveBurgers vectors b = -:-(111) and loop planes normal t o n = { llO} ( < ( b , n) = 35"). The 12 different loop orientations of this type are observed with significantly different frequencies depending sensitively on the crystallographic orientation of the specimen surface. The observations are explained in terms of the elastic interaction of the growing loops with the adjacent specimen surface. The proposed interpretation of the results leads to a critical resolved shear stress to of the order of magnitude of 10 N/mm2 for the onset of microslip in tungsten single crystals a t room temperature, in agreement with data reported in the literature. The specific stacking fault energy on { ll0}-planes is estimated as yllo = 0.8 x J/mm2. Die Bildung von Versetzungsringen vom Leerstellentyp in Wolfram, wie sie bei BeschuS mit Au-Ionen (60 keV) entstehen, wird elektronenmikroskopisch untersucht'. Fur die uberwiegende Mehrzahl der Ringe ergeben sich Burgersvektoren b = -:(111) und Normalen der Ringebenen vom Typ n = { 110) ( + ( b , n) = 35"). Die zu diesem Ringtyp gehorigen 12 verschiedenen Orientierungen werden mit deutlich verschiedenen relativen Haufigkeiten gefunden, wobei diese Haufigkeiten empfindlich von der kristallographischen Orientierung der Praparatoberflache abhangen. Die Beobachtungen werden mit der Annahme erklart, daD wahrend des JVachstums eines Leerstellenringes die elastische Wechselwirkung des Ringes mit der benachbarten Praparatoberflache eine spezifische Rolle spielt. Die vorgeschlagerie Deutung der Resultate ergibt eine kritische Schubspannung to von der GroBenordnung 10 N/mm2 fur den Einsatz der Mikrogleitung in Wolframeinkristallen bei Raumtemperatur in U'bereinstimmung mit Literaturwerten. Die spezifische Stapelfehlerenergie auf { 110}-Ebenen wird zu yllo = 0,8 x 10-6 J/mm2 abgeschatzt.

Primary radiation damage near grain boundary in bcc tungsten by molecular dynamics simulations

“…The irradiation of metals under MeV neutrons produces vacancies and interstitials [1,2] that can form clusters, such as cavities and dislocation loops, directly or indirectly [3,4,5,6]. These point defect evolution processes may lead to a series of macroscopic changes in the shape and properties of the materials, such as swelling, hardening or amorphization, which may severely affect the lifetime and reliability of the material for nuclear energy applications [7,8,9,10].…”

“…Many experiments have been done on the radiation effects on tungsten (W) [3,5,24,25]. Jäger and Wilkens observed the formation of vacancy-type dislocation loops in W produced by irradiation with 60 keV Au ions [3]. Yi et al found the formation of vacancy loops within individual cascades through a collapse process by performing in situ self-ion irradiation experiments in W and W5Re [5].…”

Electron microscope image contrast from small dislocation loops. III. Theoretical predictions for non-edge dislocation loops in a BCC crystal

“…Wilkens and co-workers at Stuttgart (Ha~sscrmann et al 1972 , J~ger andWi l kens -1975), and at Harwell (English et al 1977, Jenkins et al 1978 considerable emphasis has been pl aced on analysing small dislocation l oops formed in irradiated bcc metals since they are more complex ii terms of the possible combinations of b and n compared wi th fcc metals. In two previous papers…”

First-principles investigation of the vacancy effect on the electronic properties in M2AlC(M = V and Nb)

“…For example, in a fusion process, it is known that the fast fusion neutrons and high fluxes of ions will produce large amount of defects, which mainly consist of self-interstitial atoms and vacancies. The point defects can aggregate clusters 13 and migrate through the crystal lattice to interact with the microstructure including other point defects, solution atoms, dislocations and precipitates. The change of the microstructure under irradiation is the main cause of material degradation.…”