Fracture of complex metallic alloys: an atomistic study of model systems

Rösch, Frohmut; Trebin, Hans‐Rainer; Gumbsch, Peter

doi:10.1080/14786430500256326

Cited by 14 publications

(14 citation statements)

References 16 publications

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“…Although with this technique insight has been gained in fracture of simple structures and model systems, the situation in complex metallic alloys is less clear. In some detail only model quasicrystals and Laves phases have been investigated with model potentials (Rösch et al 2004(Rösch et al , 2005(Rösch et al , 2006.…”

Section: Introductionmentioning

confidence: 99%

Interatomic potentials and the simulation of fracture: C15 NbCr2

2006

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The discrete nature of solids and the interatomic interactions strongly influence crack propagation. Lattice trapping results in stable cracks above and below the critical Griffith load. Local atomic arrangements near the crack front define fracture behaviour. The analysis of these processes on an atomic scale helps to understand principle mechanisms and their consequences, which also have to be incorporated in more coarse-grained descriptions to get reliable results. Largescale molecular dynamics simulations of fracture on the atomic level can supply information not accessible to experiment. But to simulate a specific material reasonable effective interatomic potentials are needed. In this paper, we report on the fitting and validation of potentials specifically generated for the fracture of C15 NbCr2. Results are compared to those derived with potentials for the elements from the literature. The comparison indicates that interactions fitted to elemental metals are not sufficient to determine alloy properties

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Section: Introductionmentioning

confidence: 99%

Interatomic potentials and the simulation of fracture: C15 NbCr2

2006

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“…For this model system, detailed analyses show that indeed the clusters influence fracture behavior although they do not behave as supermolecules. Furthermore, the simulation of a related C15 Laves compound (which does not possess the clusters of the quasicrystal) gives atomically flat surfaces, whereas the quasicrystalline surfaces are rough on the cluster scale [8]. Thus, from our simulations it is evident that the inherent cluster structure is responsible for the fracture behavior of the model quasicrystal.…”

Section: Fracturementioning

confidence: 67%

Are clusters physical entities?

Rösch¹,

Trebin

2008

Zeitschrift Für Kristallographie

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Abstract. Complex metallic alloys frequently exhibit atomic clusters as structural units. In quasicrystals, they are densely arranged retaining an overall long-range quasiperiodic translational order. Thus, clusters are geometrical entities. The often posed question is, whether these are also responsible for physical properties. Fracture experiments and simulations strongly point towards a positive answer. However, a recent analysis of experimental fracture surfaces questions a signature of the clusters. From the self-affine behavior of a model system it is shown that the findings cannot vitiate the role of the clusters in the fracture process.

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“…6,9,10 Second, we shortly comment on the proposed mechanism within the process zone. Dislocation assisted fracture is indeed observed in molecular-dynamics simulations of two-dimensional quasicrystals.…”

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confidence: 99%

“…The molecular-dynamics simulations have been performed in a representative icosahedral model quasicrystal at low temperature and load. 9,10 The height of the fracture surfaces is derived by geometrical scanning. 9 The length scale in the simulations is given by r 0 , the shortest distance between two atoms in the model quasicrystal.…”

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confidence: 99%

Comment on “Cleaved surface ofi-AlPdMnquasicrystals: Influence of the local temperature elevation at the crack tip on the fracture surface roughness”

Rösch

Trebin

2008

Phys. Rev. B

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Quasicrystals are intermetallic compounds with long-range quasiperiodic translational order, composed of atomic clusters, which can be interpreted as basic geometric building blocks. It is a persistent discussion whether these clusters also represent physical entities. Cleavage planes of fractured icosahedral AlPdMn as well as sputtered surfaces annealed up to about 900 K are rough with clusterlike protrusions. Fivefold surfaces annealed at higher temperatures exhibit flat terraces. Thus, obviously, the clusters cannot be termed supermolecules. However, experiments and numerical simulations indicate that fracture is influenced by the clusters. Thus, they determine physical properties. In a recent paper, Ponson et al. ͓Phys. Rev. B 74, 184205 ͑2006͔͒ investigated experimental fracture surfaces of AlPdMn and questioned the signature of the clusters. In this comment, we study the self-affinity of cleavage planes obtained by molecular-dynamics simulations. We conclude that the findings of Ponson et al. are not excluding a physical role of the clusters in quasicrystals.One method to analyze the roughness of fracture surfaces is to calculate the height-height correlation functions. These reveal scaling properties ͑see Ref. 1 for a review paper͒ with a "universal" roughness exponent of about 0.8 for a wide range of materials. However, up to now, no theoretical model is able to satisfactorily capture this self-affinity. Thus, it is hard to interpret microscopic properties of the investigated structures starting from the scaling behavior. It might even not be possible to distinguish a fractured from a sputtered surface, as the roughness exponents of both surfaces can lie in the same range. 2,3 Although the scaling behavior of fracture surfaces seems to be universal, the range of length scales in which it is valid may strongly vary for different materials. It has been argued that the corresponding cut-off length is related to the size of the process zone R c . 4 Inside this region, linear elastic predictions do not fit the real deformation field. Such a nonlinear and dissipative zone always exists, as atomic bonds break at the crack tip. The behavior on and below this scale determines whether, how, and where a crack travels. R c should therefore be related to the microstructure. In the following, we investigate the role and interpretation of for fracture surfaces of icosahedral quasicrystals. The roughness of i-AlPdMn fracture surfaces was analyzed in a recent paper by Ponson et al. 5 They found scaling properties which resemble those of various disordered materials. The height-height correlation function reveals a selfaffine behavior from the atomic scale up to Ϸ 2 nm. The corresponding Hurst exponent H is found to be about 0.72 ͑see Fig. 2 of Ref. 5͒. The authors pointed out that the selfaffine region includes the radius of the clusters r c Ϸ 0.5 nm, which are inherent in the structure. It is stated that the morphology of the fracture surfaces therefore does not reflect the cluster distribution. Thus, the influence of th...

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Fracture of complex metallic alloys: an atomistic study of model systems

Cited by 14 publications

References 16 publications

Interatomic potentials and the simulation of fracture: C15 NbCr2

Interatomic potentials and the simulation of fracture: C15 NbCr2

Are clusters physical entities?

Comment on “Cleaved surface ofi-AlPdMnquasicrystals: Influence of the local temperature elevation at the crack tip on the fracture surface roughness”

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