On rate-dependent serrated flow behavior in amorphous metals during nanoindentation

Zhang, G.P.; Wang, W.; Zhang, B.; Tan, Jun; Liu, C.S.

doi:10.1016/j.scriptamat.2005.01.045

Cited by 53 publications

(32 citation statements)

References 19 publications

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“…7) Third, the stress/strain states of spherical elastic contacts generated by nanoindentation with a spherical indenter are very close to the ones in the real service environments of BMGs, such as the golf clubs. More importantly, the plastic deformation of BMGs during nanoindentation experiment has been found to be typically associated with serrated flow (pop-in) events, which corresponds to the operation of discrete shear bands [12][13][14] and allows precisely determining the elastic limits of BMGs by identifying the first pop-in events upon loading. By calculating the corresponding stored elastic energy and effective deformation volume, the elastic energy densities of BMGs can be readily obtained.…”

Section: Introductionmentioning

confidence: 99%

Measuring Elastic Energy Density of Bulk Metallic Glasses by Nanoindentation

et al. 2006

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The elastic energy storing capability of bulk metallic glasses was evaluated by employing depth-sensing nanoindentation. The elastic energy densities of four glassy alloys, determined by nanoindentation measurements, are fairly close to their theoretical values estimated from elastic modulus and theoretical strength. This study provides an accurate and quick method to measure the elastic properties of bulk metallic glasses.

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Section: Introductionmentioning

confidence: 99%

Measuring Elastic Energy Density of Bulk Metallic Glasses by Nanoindentation

et al. 2006

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“…Such the strain-rate dependence of serrations is widely observed in uniaxial compression and nanoindentation at ambient temperature. [14,[19][20][21][22][23][24][25]27] Unlike strain rates, the effects of temperatures on serrations are not monotonic. With increasing temperatures from 25°C to 128°C, the amplitudes of the stress variations decrease and the temporal intervals between stress peaks increase for all the strain rates.…”

Section: Resultsmentioning

confidence: 99%

“…The serrated plastic flow during the inhomogeneous deformation in metallic glasses was widely observed in various loading modes, such as compression, [8][9][10][11][12][13][14] bending, [15,16] tearing, [17,18] and nanoindentation. [5,[19][20][21][22][23][24][25][26] The formation of shear bands and serrated plastic flow are two main characteristic features of inhomogeneous deformation. Extensive investigations demonstrated that the serrated flow in metallic glasses is highly dependent on strain rates.…”

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confidence: 99%

“…Extensive investigations demonstrated that the serrated flow in metallic glasses is highly dependent on strain rates. [9,10,12,14,15,[19][20][21][22][23][24][25] Our recent work with an infrared camera demonstrated that the serrated plastic flow is a result of dynamic shear-banding operations. [14,27] Like strain rates, temperature also affects the plastic-flow behavior of metallic glasses.…”

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confidence: 99%

“…The low h/w ratio can avoid the premature fracture, facilitating an investigation on the plastic-flow behaviors in compression. [9,[21][22][23] The compression tests were performed at the ambient (25°C), elevated (128°C), and low (-196°C) temperatures, respectively. A Materials Test System (MTS) servohydraulic mechanical-testing machine was used for the compression at strain rates of 5 × 10 -2 s -1 , 1 × 10 -2 s -1 , and 2 × 10 -3 s -1 .…”

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Effects of Temperatures on Inhomogeneous Plastic Flows of a Bulk‐Metallic Glass

et al. 2008

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Since the successful vitrification of liquid metals by the rapid solidification in 1960, [1] metallic glasses have received extensive interests. The recent development of bulk-metallic glasses (BMGs) makes the applications of metallic glasses as structural materials become a reality. [2][3][4][5] However, the poor ductility and subsequent premature fracture, which are imputed to the highly-localized inhomogeneous deformation, still limit their applications. [5] At low temperatures and high strain rates, the plastic deformation of metallic glasses is known to be inhomogeneous and localized to narrow shear bands. [6,7] The formation of the shear bands affects the macroscopic plastic-flow behavior substantially. The serrated plastic flow during the inhomogeneous deformation in metallic glasses was widely observed in various loading modes, such as compression, [8][9][10][11][12][13][14] bending, [15,16] tearing, [17,18] and nanoindentation. [5,[19][20][21][22][23][24][25][26] The formation of shear bands and serrated plastic flow are two main characteristic features of inhomogeneous deformation. Extensive investigations demonstrated that the serrated flow in metallic glasses is highly dependent on strain rates. [9,10,12,14,15,[19][20][21][22][23][24][25] Our recent work with an infrared camera demonstrated that the serrated plastic flow is a result of dynamic shear-banding operations. [14,27] Like strain rates, temperature also affects the plastic-flow behavior of metallic glasses. [28] However, to our best knowledge, little work has addressed this topic, which may have fundamental interest and practical significance for metallic glasses.As an extension of our previous work, [28] this paper presents an investigation on the plastic flow and shear banding of a Zr-based BMG at various strain rates at the ambient (25°C), elevated (128°C), and low (-196°C) temperatures. The results may improve understanding of inhomogeneousdeformation behaviors of BMGs. ExperimentalThe (Zr 0.55 Al 0.1 Ni 0.05 Cu 0.3 ) 98 Er 2 (atomic percent, at.%) BMG was used in this investigation. This Zr-based BMG with addition of Er has a good glass-forming ability. [29] The BMG was prepared by arc-melting pure elements in a purified argon atmosphere, followed by casting in a water-cooled copper mold. The resulting ingots have a dimension of 70 mm × 3 mm × 3 mm. The amorphous structure of the ascast specimens was confirmed by the X-ray diffraction with the Cu Ka radiation. Differential-scanning calorimetry (DSC) was used to characterize its thermal properties. DSC was run two times for each specimen from 50°C to 600°C at the heating rate of 20°C/min. in an argon atmosphere. DSC shows that the glass-transition (T g ) and crystallization (T x ) temperatures for the as-cast BMG are 401°C and 493°C, respectively. This result is close to the previous work. [29] The compressiontest specimens have a dimension of 2 mm × 3 mm × 3 mm, with a height (h)/width (w) ratio of 0.67. The low h/w ratio can avoid the premature fracture, facilitating an investigation o...

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Effect of annealing temperature on interrelation between the microstructural evolution and plastic deformation in polymers

Malekmotiei

Voyiadjis

Samadi-Dooki

et al. 2017

J. Polym. Sci. Part B: Polym. Phys.

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The mechanical loading induced flow of glassy polymers is triggered by the nucleation of shear transformation units, and strongly depends on the initial microstructural state of the material. Therefore, investigation of the possible relationship between the microstructural state variables and plastic deformation is required for a better understanding of the macroscopic response of this class of materials during large deformation. In this study, free volume content is considered as a state variable and thermal treatment is selected as a process through which the accelerated and forced evolution of the free volume can be imposed. For two well-known glassy polymers, poly(methyl methacrylate) and polycarbonate, the free volume content alteration upon annealing is monitored via positron annihilation spectroscopy, and the changes of the micro-and macromechanical properties are also obtained by utilizing nanoindentation technique and employing the homogeneous amorphous flow theory. The correlation between the microstructural state variable, that is, free volume, and the micromechanical state variable, that is, shear activation volume, is then investigated. The results reveal opposite direction of alterations of free volume and shear activation volume with annealing temperature. Accordingly, the possibility of the existence of an interrelation between these two state variables is critically discussed.

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On rate-dependent serrated flow behavior in amorphous metals during nanoindentation

Cited by 53 publications

References 19 publications

Measuring Elastic Energy Density of Bulk Metallic Glasses by Nanoindentation

Measuring Elastic Energy Density of Bulk Metallic Glasses by Nanoindentation

Effects of Temperatures on Inhomogeneous Plastic Flows of a Bulk‐Metallic Glass

Effect of annealing temperature on interrelation between the microstructural evolution and plastic deformation in polymers

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