Deformation behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass over a wide range of strain-rates and temperatures

Lu, Jun; Ravichandran, G.; Johnson, William L.

doi:10.1016/s1359-6454(03)00164-2

Cited by 711 publications

(620 citation statements)

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“…1a) of materials increases at lower temperatures, showing the strengthening behavior at T > 20 K. On the other hand, the increase in the critical shear stress will in turn improve the dilatation ability of STZs, since the STZ has the nature of shear thinning or -dilatation due to the disordered structure. This picture is supported by the common observation that metallic glasses with higher strengths are always accompanied by a more significant softening to cracking [53][54]. Therefore, the STZ at lower temperatures becomes more inclined to dilatation operations, macroscopically corresponding to the decrease in the critical normal tensile stress r 0 (Fig.…”

Section: Discussionmentioning

confidence: 53%

Cryogenic-temperature-induced transition from shear to dilatational failure in metallic glasses

et al. 2014

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Section: Discussionmentioning

confidence: 53%

Cryogenic-temperature-induced transition from shear to dilatational failure in metallic glasses

et al. 2014

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“…22 The coefficients of Eq. ͑7͒ are given by a 0 =4͑2−T / T g ͒⌬G, b 0 =−32⌬G, and c 0 =16⌬G, where the AVD activation energy ⌬G is estimated as 4.6 eV at T = 300 K. 23 We choose a 1 = 4 and b 1 = −9 to quantitatively describe the shear softening in glassy alloy, which is consistent with experiments and MD simulation. 17,21 In particular, such chosen coefficients reflect the fact that the shear modulus tends to decrease and approaches zero when ͑r ជ͒ → 1.…”

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confidence: 57%

Mesoscopic theory of shear banding and crack propagation in metallic glasses

Zheng

2009

Phys. Rev. B

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We propose a phenomenological theory to model shear banding, shear-band propagation and branching on mesoscopic scales in metallic glasses by using Ginzburg-Landau formulism. The disordering caused by mechanical or thermal agitation is represented by atomic volume dilatation and used as an order parameter. This model captures several important features in the deformation process, namely, shear localization or banding, shear-band propagation and branching, and crack propagation and its velocity. We also assessed the relation between the crack propagation velocity and local heating and the connection between the serrated flow and shear band branching. DOI: 10.1103/PhysRevB.80.104201 PACS number͑s͒: 62.25.Mn, 46.50.ϩa, 61.43.Bn, 61.43.Fs One of the most promising developments in metallic materials in recent years is the invention of bulk metallic glasses ͑BMGs͒. 1,2 BMGs are topologically disordered solids without the long-range translational order as seen in crystalline materials. The disordered structure with atoms packed randomly leads to many unique and outstanding properties. Perhaps the most interesting is the phenomenon called shear localization: when a metallic glass subject to external load reaches the flow stress, plastic deformation occurs in narrow bands. The deformation strain inside the band is many times larger than that outside, causing samples to fail locally and quickly. The shear localization is by far identified as the only mechanism that affects the strength, ductility, and thus application of the BMGs which otherwise have many potential applications derived from the superb properties. 1-4 Shear banding consists of three stages: nucleation, growth and propagation, and final failure; and each stage occurs on a different spatial and temporal scale. Shear-band nucleation occurs in less than microsecond and with the critical nucleation size of about 10 to several hundred nanometers, depending on the material and ambient conditions. 1-5 Once the critical state is approached, the band could grow and propagate; the bands grow into steady state, or maturity with typical thickness of tens of nanometers to hundreds of nanometers and length of many times larger than the thickness, depending on the propagation condition. 1-5 A propagating shear band often becomes unstable, resulting in branching into subbands. [1][2][3][4][5] The mechanical properties of metallic glasses are determined by the detailed behavior of the shearband evolution. For example, a shear band starting propagating would affect yielding, or strength, and its propagation and branching would contribute to ductility as more deformation is concentrated inside the bands, absorbing more deformation energy and thus contributing to higher toughness. In addition, as we identify below, shear-band branching may be a major reason for the serrated flow observed during plastic deformation.The evolution exhibited in a localized shear band is a complex interplay of many factors. The initiation of a shear band is related to the local stress concentra...

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“…The loading setup described in Ref. 13 is utilized. Deformation was performed for a period of time sufficient to allow a steady flow stress state in the nonNewtonian regime to be attained.…”

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Deformation of glass forming metallic liquids: Configurational changes and their relation to elastic softening

Harmon¹,

Demetriou²,

Johnson³

et al. 2007

Applied Physics Letters

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The change in the configurational enthalpy of metallic glass forming liquids induced by mechanical deformation and its effect on elastic softening is assessed. The acoustically measured shear modulus is found to decrease with increasing configurational enthalpy by a dependence similar to one obtained by softening via thermal annealing. This establishes that elastic softening is governed by a unique functional relationship between shear modulus and configurational enthalpy. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2717017͔In the recent work of Johnson and co-workers, 1-4 a link between elastic softening and configurational changes in metallic glass forming liquids has been proposed. The steepness of the viscosity dependence on temperature in the vicinity of the glass transition, i.e., the liquid fragility, has been known to be associated with the stored configurational enthalpy since the early work of Angell and co-workers. [5][6][7] Furthermore, the effect of strain rate on viscosity induced by mechanical deformation has also been linked to changes in configurational enthalpy. 8 However, attributing the deformationally induced softening of liquids to a unique functional relation between shear modulus and stored configurational enthalpy is a concept that has just recently been brought to attention. 3 This concept essentially suggests that conversion of mechanical work into stored configurational enthalpy induces softening via a dependence of shear modulus on configurational enthalpy. The thermodynamic state variable controlling flow in this concept is identified to be the isoconfigurational shear modulus. Experimental validation of earlier concepts based on the "free volume" hypothesis 9 has not been possible, mainly due to the lack of a fundamental thermodynamic definition of free volume. In contrast, the isoconfigurational shear modulus is a thermodynamically well-defined and experimentally accessible property, rendering this concept experimentally verifiable. In the present study, the change in configurational enthalpy induced by mechanical work and its effect on the softening of metallic glass forming liquids is evaluated by means of compressive experiments, ultrasonic measurements, and enthalpy recovery tests.For the loading experiments we utilized cylindrical specimens of Pt 57.2 Ni 5.3 Cu 14.7 P 22.5 ͑Refs. 10 and 11͒ and Pd 43 Ni 10 Cu 27 P 20 , 3,12 which we deformed isothermally at constant strain rates. The loading setup described in Ref. 13 is utilized. Deformation was performed for a period of time sufficient to allow a steady flow stress state in the nonNewtonian regime to be attained. Upon unloading, the specimens were quenched as rapidly as possible to capture the configurational state associated with that flow stress.We assessed the elastic softening induced by mechanical deformation by evaluating the isoconfigurational shear modulus at the high-frequency "solidlike" limit G. We evaluated G of the quenched unloaded specimens ultrasonically, 14 and extrapolated the room temperature m...

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Deformation behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass over a wide range of strain-rates and temperatures

Cited by 711 publications

References 34 publications

Cryogenic-temperature-induced transition from shear to dilatational failure in metallic glasses

Cryogenic-temperature-induced transition from shear to dilatational failure in metallic glasses

Mesoscopic theory of shear banding and crack propagation in metallic glasses

Deformation of glass forming metallic liquids: Configurational changes and their relation to elastic softening

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