A model of the ductile–brittle transition of partially crystallized amorphous Al–Ni–Y alloys

Kim, H.S.; Hong, Sun Ig

doi:10.1016/s1359-6454(99)00088-9

Cited by 69 publications

(16 citation statements)

References 18 publications

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“…It has been suggested that annealing-induced embrittlement of an amorphous alloy occurs when the solute content at the amorphous/crystal interface reaches a critical value. [24] This concept of a critical interfacial composition, leading to a ductile-brittle transition, is supported by the comparison of the results in the present work (with no observed increase in solute content at the interface) with those on alloys where the nanocrystallization is induced by annealing. The diffusivity of samarium is likely to be very low at the annealing temperature of the amorphous alloys, and the Sm atoms rejected from fcc-Al particles cannot stray far from the interface region.…”

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confidence: 77%

Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

et al. 2007

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The discovery of Al-based metallic glasses has generated fundamental and practical interest since these amorphous alloys crystallize to a nanostructured composite containing face-centred-cubic (fcc) nanometre-sized aluminium crystallites (diameter < 20-30 nm) embedded in an amorphous matrix. [1,2] They show remarkable mechanical properties, potentially useful for engineering applications. [3][4][5][6] For example, the nanocomposite aluminium alloys produced by rapid solidification and subsequent annealing of Al-TM-RE alloys (TM: transition metal; RE: rare earth) show ultra-high tensile fracture strength: for the Al 88 Ni 9 Fe 1 Ce 2 nanophase composite, the strength at room temperature is as high as 1.56 GPa far above the highest strength of conventional wrought aluminium alloys. [5] The properties are strongly related to the volume fraction of the nanocrystallized fcc-Al particles in the amorphous matrix. We have previously presented our investigations [7][8][9] concerning the glass-forming ability, nanocrystallization and the mechanical properties (hardness and wear resistance) of alloys prepared within the Al-Ni-Sm system. Because of the excellent mechanical properties, enhanced by a nanocrystallite dispersion, one strategy has been to control the primary crystallization (devitrification) by annealing the fully amorphous as-quenched state. [10] The nanocomposites obtained by devitrification of amorphous Al 88 Ni 4 Sm 8 were found to provide very stable materials with rather good ductility in the temperature range corresponding to the primary crystallization. In this alloy, a high density of nanocrystallites with a dendritic-like shape of about 20-30 nm was observed uniformly distributed in the remaining amorphous matrix. [11] A very similar observation on the Al 92 Sm 8 alloy showed the density of nanoparticles crystallized under thermal treatment to be ∼ 10 21 m -3 . [12] Several proposals involving solute effects, phase separation or quenched-in nuclei and heterogeneous nucleation have been advanced to account for the high nanocrystal density. [13][14][15][16] The strengthening in such materials has been explained in terms of the defect-free nanoscale Al particles (which would have higher flow stress than the amorphous phase) homogeneously dispersed in the amorphous matrix acting as effective barriers to the shear banding of the matrix. [17] However, it was also suggested that the hardening effect could be attributed to solute enrichment of the remaining glassy matrix and not exclusively due to the presence of the nanoparticles themselves. [6,18] Unfortunately, the rather good room-temperature bending ductility of the fully amorphous as-quenched state is progressively reduced by annealing into the nanocrystalline state. Plasticity is very important for many shaping and forming operations and for avoiding catastrophic failure in load-bearing applications. Although these nanostructured alloys possess exceptionally high strength, a compromise must be found in the development of such materials for engineering ap...

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confidence: 77%

Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

et al. 2007

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“…No mechanistic explanations were oered for this drop in Zr alloys. For the case of the Al±Ni±Y system, Kim and Hong [41] proposed a model for the ductile±brittle transition, which assumes the material becomes brittle when the solute (Y) concentration in the Al particle/amorphous matrix interlayer reaches a critical value.…”

Section: Fracture Mechanismsmentioning

confidence: 99%

Effect of crystallinity on the impact toughness of a La-based bulk metallic glass

et al. 2000

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“…Following the discovery of new bulk metallic glass (BMG) alloy systems, significant progress has been made in their processing and the understanding of their fundamental properties [1][2][3][4][5][6]. However, there is still a need to establish their mechanical behaviour in terms of both quantitative and qualitative description.…”

Section: Introductionmentioning

confidence: 99%

Fictive stress model based finite element analysis for bulk metallic glasses at an elevated temperature

Kim

2004

Met. Mater. Int.

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It is important to manufacture micromachine parts and simulate the deformation behavior of bulk amorphous alloys in a supercooled liquid region. For these purposes, a correct constitutive model that can reproduce viscosity results is essential for good predictive capability. In this paper, finite element analyses of nonlinear behaviour in bulk metallic glasses during die compression in the supercooled liquid region have been carried out based on the fictive stress model in conjunction with the Maxwell viscoelastic model. The friction effect between the work piece and the die played an important role in inhomogeneous deformation.

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A model of the ductile–brittle transition of partially crystallized amorphous Al–Ni–Y alloys

Cited by 69 publications

References 18 publications

Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

Effect of crystallinity on the impact toughness of a La-based bulk metallic glass

Fictive stress model based finite element analysis for bulk metallic glasses at an elevated temperature

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A model of the ductile–brittle transition of partially crystallized amorphous Al–Ni–Y alloys

Cited by 69 publications

References 18 publications

Nanocrystallized Al92Sm8 Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

Nanocrystallized Al92Sm8 Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

Effect of crystallinity on the impact toughness of a La-based bulk metallic glass

Fictive stress model based finite element analysis for bulk metallic glasses at an elevated temperature

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Product

Resources

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Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis

Nanocrystallized Al₉₂Sm₈ Amorphous Alloy Investigated by High‐Resolution Microscopy and 3D Atom‐Probe Analysis