Structural relaxation and plastic flow in amorphous La50Al25Ni25

Aken, B.B. van; Hey, Paul de; Sietsma, Jilt

doi:10.1016/s0921-5093(99)00574-2

Cited by 45 publications

(42 citation statements)

References 15 publications

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“…The creation and annihilation of free volume during structural relaxation of amorphous alloys is both a kinetic and a thermodynamic process. With the assumption that the heat release rate of an amorphous material is proportional to the rate of creation of free volume, a group of researchers 7,23,24 studied the free volume evolution during high-temperature deformation and concluded that the free volume increases with strain rate and strain until steady-state flow occurs, which agrees with the experimental observations in this investigation.…”

Section: Discussionsupporting

confidence: 84%

“…Some investigators believe it to be direct evidence of free volume concentration in the material at the beginning of the DSC scans. 7,23,24 Such a hypothesis provides a good explanation for the present results, which is discussed later. By comparing the enthalpy change during the crystallization process of the deformed (designated by the subscript "def") samples and that of the as-cast (designated by the superscript "a-c") sample, the fraction of crystallization in the materials can be estimated as…”

Section: B Dsc Resultssupporting

confidence: 69%

“…It is a complicated process with intrinsic structural instability of the material and the interaction between its thermomechanical behavior and microstructural changes. Based on extensive experimental results for a wide range of metallic glasses including Zr-based alloys, [3][4][5] La-based alloys, 6,7 Fe-based alloys, 8,9 and Pdbased alloys, [10][11][12] three distinctly different deformation modes can be observed and described using their empirical flow characteristics: shear localization, occurring at room temperature and with high strain rate and featuring limited plasticity accumulated in localized thin shear bands; non-Newtonian flow, occurring at some moderate temperature in the vicinity of glass transition temperature (T g ) of the material and featuring stress over-and undershooting before steady-state stress is reached; and Newtonian flow, occurring in supercooled liquid regime of the material (above T g and below crystallization temperature T x ) and featuring steady-state flow once yield starts. The first mode (shear localization) is an inhomogeneous flow mode, whereas the last two (non-Newtonian and Newtonian flow) are homogeneous flow modes.…”

Section: Introductionmentioning

confidence: 99%

“…23 de Hey et al applied the same idea to temperature-induced structural evolution of some metallic glasses, leading to the conclusion that additional free volume was created compared with thermal equilibrium due to plastic deformation. 7,24 Adopting the free volume concept, Anand and Su extended their elastic-viscoplastic constitutive model 25 for metallic glass deformed at room temperature to high temperature homogenous flow regime 26 and applied it to capture the stress over-and undershort phenomena in non-Newtonian flow observed in earlier experiments. 24 The recent developments in technology have provided advanced tools to experimentally study the complicated phenomena associated with crystallization and structural relaxation in BMGs at the microstructural level resulting from thermal or mechanical loading.…”

Section: Introductionmentioning

confidence: 99%

“…[30][31][32] In the homogeneous flow region, de Hey et al further associated the glass transition behavior in the DSC trace of the deformed specimen with the amount of free volume and used it to explain the deformation behavior of Pdand La-based alloys. 7,23,24 Heggen et al used compression creep testing at constant stress and during jump stress to study the structural relaxation and disordering during the high-temperature deformation of a Pd-NiCu-P alloy, from the perspective of free volume creation and annihilation. 33,34 Nieh et al suggested nanocrystallization in the amorphous structure during the homogeneous deformation based on x-ray diffraction and TEM examinations of the superplastically deformed specimens.…”

Section: Introductionmentioning

confidence: 99%

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Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

et al. 2010

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The purpose of this study is to experimentally investigate the interaction of inelastic deformation and microstructural changes of two Zr-based bulk metallic glasses (BMGs): Zr 41.25 Ti 13.75 Cu 12.5 Ni 10 Be 22.5 (commercially designated as Vitreloy 1 or Vit1) and Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 (Vitreloy 4, Vit4). High-temperature uniaxial compression tests were performed on the two Zr alloys at various strain rates, followed by structural characterization using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Two distinct modes of mechanically induced atomic disordering in the two alloys were observed, with Vit1 featuring clear phase separation and crystallization after deformation as observed with TEM, while Vit4 showing only structural relaxation with no crystallization. The influence of the structural changes on the mechanical behaviors of the two materials was further investigated by jump-in-strain-rate tests, and flow softening was observed in Vit4. A free volume theory was applied to explain the deformation behaviors, and the activation volumes were calculated for both alloys.

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Section: Discussionsupporting

confidence: 84%

Section: B Dsc Resultssupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

et al. 2010

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Elevated Temperature Deformation Behavior of Zr‐Based Bulk Metallic Glasses

Heilmaier

Eckert

2005

Adv Eng Mater

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Within the last decade, metallic glassy alloys in bulk form produced by slow cooling from the melt [1±4] have attracted widespread interest ranging from scientific curiosity about the structure and the resulting properties to technological aspects of preparation and potential applications. In contrast to binary and ternary amorphous metallic systems produced in form of thin ribbons, these multi-component alloys are characterized by a strong glass-forming ability (GFA) together with a wide supercooled liquid region, thus giving rise to a high thermal stability against crystallization. This enables the production of bulk glassy samples with a thickness of up to 75 mm by conventional casting techniques. [13] Besides their thermodynamic properties Zr-based bulk metallic glasses (BMGs) in particular reveal outstanding mechanical properties at room temperature, [5±8] namely a beneficial combination of yield strength values as high as those known for high-strength structural steels, microplasticity of up to 1 %, low Young's moduli and high fracture toughness values comparable to those of aluminum alloys. The desirable properties of the amorphous phase together with the reported easy forming and shaping ability in the viscous state at elevated temperatures above the glass transition [11] promise applications in the field of near-net shape fabrication of structural components. [12,13] In the present work, we will review the deformation mechanism in the supercooled liquid state, since it is of paramount importance to identify and assess the temperature COMMUNICATIONS ADVANCED ENGINEERING MATERIALS 2005, 7, No. 9

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Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

Chen

Liu

Chan

2008

Sci. China Ser. G-Phys. Mech. As

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A Zr-based bulk metallic glass (BMG) with a composition of (Zr 75 Cu 25 ) 78.5 Ta 4 Ni 10 Al 7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr 75 Cu 25 ) 74.5 Ta 8 Ni 10 Al 7.5 have been prepared by copper-mold casting. The compressive deformation behavior of the BMG and BMGC was investigated in the supercooled region at different temperatures and various strain rates ranging from 8×10 −4 s −1 to 8×10 −2 s −1 . It was found that both the strain rate and test temperature significantly affect the deformation behavior of the two alloys. The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism for the two kinds of alloys was discussed in terms of the transition state theory.bulk metallic glass, composites, supercooled liquid region, compressive deformation, free volume

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Structural relaxation and plastic flow in amorphous La50Al25Ni25

Cited by 45 publications

References 15 publications

Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

Deformation and crystallization of Zr-based amorphous alloys in homogeneous flow regime

Elevated Temperature Deformation Behavior of Zr‐Based Bulk Metallic Glasses

Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

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