Primary damage formation in molybdenum: A computer simulation study

Pasianot, R.C.; Alurralde, M.; Almazouzi, A.; Victoria, M.

doi:10.1080/01418610208235683

Cited by 16 publications

(20 citation statements)

References 29 publications

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“…When the stochastic fluctuations dominate the kinetics of random voids, while the evolution of the RIF voids is determined by the mean-field growth, the value of Gt cs is also the characteristic dose required for the void lattice formation. Thus, in agreement with experimental observations, 3,48 the nominal dose Kt cs for void lattice formation is on the order of 10 NRT dpa ͑G / K Х 0.3 43,45 ͒.…”

Section: ͑37͒supporting

confidence: 72%

“…45 However, most of the clusters produced in 20 and 30 keV cascades are di-and tri-interstitials, the morphology of which is ill defined but shows sessile features. 45 Only clusters of five and more interstitials have structures comparable to prismatic loop embryos, which may be assumed to be mobile. However, few of such clusters are actually produced in the cascades.…”

Section: S ͑27͒mentioning

confidence: 99%

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Void lattice formation as a nonequilibrium phase transition

Семенов

Woo

2006

Phys. Rev. B

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The evolution of a void ensemble in the presence of one-dimensionally migrating self-interstitials is considered, consistently taking into account the nucleation of voids via the stochastic accumulation of vacancies. Including the stochastic fluctuations of the fluxes of mobile defects caused by the random nature of diffusion jumps and cascade initiation, the evolution of the void ensemble is treated using the Fokker-Planck equation approach. A system instability signaling a nonequilibrium phase transition is found to occur when the mean free path of the one-dimensionally moving self-interstitials becomes comparable with the average distance between the voids at a sufficiently high void-number density. Due to the exponential dependence of the void nucleation probability on the net vacancy flux, the nucleation of voids is much more favored at the void lattice positions. Simultaneously, voids initially nucleated at positions where neighboring voids are nonaligned will also shrink away. These two processes leave the aligned voids to form a regular lattice. The shrinkage of nonaligned voids is not a usual thermodynamic effect, but is a kinetic effect caused entirely by the stochastic fluctuations in point-defect fluxes received by the voids. It is shown that the shrinkage of the nonaligned voids, and thus the formation of the void lattice, occurs only if the effective fraction of one-dimensional interstitials is small, less than about 1%. The formation of the void lattice in this way can be accomplished at a void swelling of below 1%, in agreement with experimental observation. The dominance of void nucleation at void-lattice positions practically nullifies the effect of void coalescence induced by the one-dimensional selfinterstitial transport.

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Section: ͑37͒supporting

confidence: 72%

Section: S ͑27͒mentioning

confidence: 99%

Void lattice formation as a nonequilibrium phase transition

Семенов

Woo

2006

Phys. Rev. B

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“…[10][11][12]18,24,25,[27][28][29] Cascades in Mo were studied in Ref. 26. Most of the MD results on radiation damage were obtained within the PKA model, and the influence of the surface attracted less attention.…”

Section: Introductionmentioning

confidence: 99%

Radiation-induced damage and evolution of defects in Mo

et al. 2011

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The formation of defects in bcc Mo lattice as a result of 50-keV Xe bombardment is studied via atomistic simulation with an interatomic potential developed using the force-matching ab initio based approach. The defect evolution in the cascade is described. Diffusion and interaction of interstitials and vacancies are analyzed. Only small interstitial atom clusters form directly in the cascade. Larger clusters grow only via aggregation at temperatures up to 2000 K. Stable forms of clusters demonstrate one-dimensional diffusion with a very high diffusion coefficient and escape quickly to the open surface. Point vacancies have much lower diffusivity and do not aggregate. The possibility of a large prismatic vacancy loop formation near the impact surface as a result of fast recrystallization is revealed. The mobility of the vacancy dislocation loop segments is high, however, the motion of the entire loops is strongly hindered by neighbor point defects. This paper explains the existence of the large prismatic vacancy loops and the absence of the interstitial loops in the recent experiments with ion irradiation of Mo foils.

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“…Three-dimensional vacancy clusters which are still small (n ∼ n min + 1) but immobile (microvoids) are homogeneously produced either directly in the collision cascades [31][32][33] or via the consecutive agglomeration of single vacancies. This is taken into account by the source term j 0 in (1), where the δ-function represents the assumption that initially all microvoids are of the same size n 0 (= n min + 1).…”

Section: Void Number Density and Size Distribution Of A Random Ensemblementioning

confidence: 99%

“…8, the lifetime Kτ s of a random void (φ = 1) and voids with one overlapping ISC (φ = 7/8) are significantly shorter than the lifetime of voids with two overlapping ISCs (φ = 6/8), which still does not exceed just a few NRT dpa. Here K is the nominal NRT rate of displacements per atom (dpa) (G/K ∼ = 0.3 [33,39]). Note that, for an initially random void distribution, the positions on a close-packed plane, where nucleating voids can have two overlapping ISCs, occupy a volume fraction of q s ≈ 2S.…”

Section: Shrinkage Of Voids In Non-lattice Positionsmentioning

confidence: 99%

Diffusion anisotropy and void development under cascade irradiation

2008

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Cascade irradiation of metals gives rise to swelling as a result of the creation of voids and the evolution of the void ensemble. Under suitable circumstances, the originally disordered void distribution transforms into to a void lattice. As demonstrated previously, the understanding of the evolution and the unique features of the void ensemble requires a difference in the anisotropy of the diffusion (DAD) of vacancies and self-interstitial atoms (SIAs), which is achieved by one-dimensional diffusion of the SIAs. On the other hand, void swelling has been successfully modeled in terms of three-dimensional diffusion of both vacancies and SIAs. In the present paper it is shown that these seemingly contradicting interpretations and all related observations can be quantitatively reconciled by a small DAD created by only ∼1% of SIAs diffusing one-dimensionally. It is also demonstrated that at the initial stage of void-lattice formation, ordering occurs mainly on close-packed crystal planes, which is in contrast to the naïve expectation that one- A difference between the anisotropies of diffusion of vacancies and self-interstitials (henceforth called Diffusional Anisotropy Difference or, briefly, DAD) gives rise to a bias that plays an important role in the irradiation-induced evolution of microstructures in metals. Based on Gösele's work [1] on reaction kinetics, the DAD effect was first introduced by Woo and Gösele [2] to explain irradiation growth. Later irradiation creep and void-lattice formation were interpreted in terms of DAD by Woo [3] and Woo and Frank [4], respectively, before DAD has been promoted to an important concept in the treatment of irradiation damage in non-cubic metals by Woo [5,6].The role played by DAD in the irradiation-induced transformation of a void ensemble from a randomly distributed collection to a highly ordered void lattice was summarized by Woo and Frank [7]: ". . . the one-dimensional migration of the (interstitial) crowdions. . . is in marked contrast to the three-dimensional diffusion of the dumbbell interstitials and the vacancies. This diffusional anisotropy difference between the crowdions and vacancies provides the source of ordering via a Darwinian selection among randomly distributed voids." Hence, the strength of DAD is important to the behavior of a void ensemble under irradiation, and at the same time, the evolution of the void ensemble reflects the

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Primary damage formation in molybdenum: A computer simulation study

Cited by 16 publications

References 29 publications

Void lattice formation as a nonequilibrium phase transition

Void lattice formation as a nonequilibrium phase transition

Radiation-induced damage and evolution of defects in Mo

Diffusion anisotropy and void development under cascade irradiation

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