Enhanced toughness due to stable crack tip damage zones in bulk metallic glass

Flores, Katharine M.; Dauskardt, Reinhold H.

doi:10.1016/s1359-6462(99)00243-2

Cited by 143 publications

(79 citation statements)

References 10 publications

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“…[5][6][7][8][9] In an additional study however in which single-edge notched tension (SENT) was used, the fracture toughness of Vitreloy 1 was reported to be in excess of 130 MPaÁm 1/2 . 10 Such an extremely high toughness is surprising, given that the tension loading geometry of SENT is geometrically less confined than the bending loading geometry of CT and SENB. The unusual combination of zero ductility but high fracture toughness of BMGs was also pointed out by Ashby and Greer.…”

Section: Introductionmentioning

confidence: 99%

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

et al. 2010

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Fracture surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant "plastic zone" screening at the crack tip.

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Section: Introductionmentioning

confidence: 99%

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

et al. 2010

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“…However, in ductile fracture the energy release rate also includes large-scale plastic dissipations around the crack tip region. Decomposition of the energy release rate into the elastic, , and plastic, , components decouples the work required for material separation from the energy dissipation due to large-scale plasticity around the crack tip region [25,[37][38][39][40]. The elastic component of the critical energy release rate, , which is the energy needed for material debonding per unit area of the crack advance, is considered as the cohesive energy of a ductile material [37].…”

Section: Resultsmentioning

confidence: 99%

“…Under the tensile loading, two slip shear bands are formed and developed at a ±55° angle with respect to the loading axis. In bending, the slip bands form a fan-shaped curvature known as Prandtl slip fields [40]. Furthermore, the crack tip plastic zones at failure, which are estimated by the cohesive zone FE model for the SENB and SENT specimens, are superposed on the optical micrographs taken from the specimen side surface near the crack after the fracture tests, as is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Cohesive zone modeling of ductile tearing process in brazed joints

Ghovanlou

Jahed

Khajepour

2013

Engineering Fracture Mechanics

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“…18 With a J-based analysis, section sizes essentially met validity; the current K Jc values are thus deemed to be accurate and representative of the toughness of these materials. Consequently, in comparison to monolithic BMG alloys, where K Ic can be as low as 20 MPaͱ m, [20][21][22] we can now state with assurance that these metallic glass-matrix composites exhibit toughnesses that are significantly higher than for monolithic BMGs, and further are comparable to the toughest crystalline metallic alloys at these high strength levels ͑Ͼ1 GPa͒.…”

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confidence: 93%

Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites

Launey

Hofmann

Suh

et al. 2009

Applied Physics Letters

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Nonlinear-elastic fracture mechanics methods are used to assess the fracture toughness of bulk metallic glass ͑BMG͒ composites; results are compared with similar measurements for other monolithic and composite BMG alloys. Mechanistically, plastic shielding gives rise to characteristic resistance-curve behavior where the fracture resistance increases with crack extension. Specifically, confinement of damage by second-phase dendrites is shown to result in enhancement of the toughness by nearly an order of magnitude relative to unreinforced glass. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3156026͔The absence of microstructure in monolithic bulk metallic glasses ͑BMGs͒ can lead to marked strain localization and rapid shear-band propagation. 1,2 This effect, which causes extremely low macroscopic plastic deformability, can be devastating to mechanical performance in that properties that are limited by the extension of cracks, such as tensile ductility, toughness, and fatigue resistance, can become severely compromised. Specifically, unstable fracture can ensue in monolithic BMGs along a single shear band with essentially zero macroscopic ductility, 3,4 such that the toughness is far lower than in comparable crystalline alloys. The essential element to developing high toughness in BMGs is to prevent single shear-band failures. By introducing a second phase in form of crystalline dendrites and by matching microstructural length scales ͑i.e., interdendritic spacing͒ to the mechanical length scales ͑i.e., critical crack size for failure͒, nonlocalized plasticity in metallic glasses can be enhanced significantly. [5][6][7] Indeed, the recent development of in situ bulk metallic glass-matrix composites has shown that provided this phase acts to arrest shear-band propagation over appropriate size scales, 8-10 the problems of poor ductility, toughness, and fatigue resistance can be mitigated.One problem here is that the new composite BMGs are undoubtedly far tougher than monolithic BMGs or some earlier BMG composites and current processing methods often cannot make section sizes large enough to meet the critical validity requirements for accurate fracture mechanics measurements, i.e., not meeting fracture mechanics requirements for valid stress intensity K-or J-dominated crack-tip fields and/or for plane-strain constraint. Indeed, many toughness measurements on BMG materials reported in the literature [11][12][13][14][15] are inaccurate due to problems of inappropriate measurement techniques ͑e.g., the area under a compression stress/strain curve͒, absence of sharp stress concentrators ͑e.g., using a relatively blunt notch rather than a fatigue precrack͒ and insufficient test-sample size. Moreover, while single-value measurements, such as K Ic , properly define the toughness of nominally brittle materials, they can be insufficient for alloys displaying extensive plastic deformation and subcritical cracking, as can occur in many BMG composites. Stable crack growth in metallic glasses is not generally observed and ...

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Enhanced toughness due to stable crack tip damage zones in bulk metallic glass

Cited by 143 publications

References 10 publications

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

Cohesive zone modeling of ductile tearing process in brazed joints

Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites

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