Low-temperature irreversible structural relaxation of amorphous metallic alloys

Zaichenko, S.G.; Перов, Н. С.; Глезер, А. М.; Ганьшина, Е. А.; Kachalov, V. M.; Calvo-Dalborg, M; Dalborg, U

doi:10.1016/s0304-8853(00)00138-4

Cited by 26 publications

(12 citation statements)

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“…Ketov et al [26] have suggested that rejuvenation is associated with thermal cycling and not with ongoing change at 77 K. The measured effects on magnetic properties [39,40], however, show that a longer hold at 77 K can have a greater effect, and this merits study for cycling treatments.…”

Section: Stored Energy From Thermal Cyclingmentioning

confidence: 98%

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Stored energy in metallic glasses due to strains within the elastic limit

Greer

Sun

2016

Philosophical Magazine

112

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Room temperature loading of metallic glasses, at stresses below the macroscopic yield stress, raises their enthalpy and causes creep. Thermal cycling of metallic glasses between room temperature and 77 K also raises their enthalpy. In both cases, the enthalpy increases are comparable to those induced by heavy plastic deformation, but, as we show, the origins must be quite different. For plastic deformation, the enthalpy increase is a fraction (<10%) of the work done (WD) (and, in this sense, the behaviour is similar to that of conventional polycrystalline metals and alloys). In contrast, the room temperature creep and the thermal cycling involve small strains well within the elastic limit; in these cases, the enthalpy increase in the glass exceeds the WD, by as much as three orders of magnitude. We argue that the increased enthalpy can arise only from an endothermic disordering process drawing heat from the surroundings. We examine the mechanisms of this process. The increased enthalpy ('stored energy') is a measure of rejuvenation and appears as an exothermic heat of relaxation on heating the glass. The profile of this heat release (the 'relaxation spectrum') is analysed for several metallic glasses subjected to various treatments. Thus, the effects of the small-strain processing (creep and thermal cycling) can be better understood, and we can explore the potential for improving properties, in particular the plasticity, of metallic glasses. Metallic glasses can exhibit a wide range of enthalpy at a given temperature, and small-strain processing may assist in accessing this for practical purposes.

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Section: Stored Energy From Thermal Cyclingmentioning

confidence: 98%

“…There were earlier reports [39][40][41][42] of the effects of cryogenic treatments (single holds for various times at 77 K). The reported effects include reduced yield stress and Young modulus [40].…”

Section: Stored Energy From Thermal Cyclingmentioning

confidence: 99%

Stored energy in metallic glasses due to strains within the elastic limit

Greer

Sun

2016

Philosophical Magazine

112

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“…in Ref. [13]. The sample storage at low temperature such as 77 K, may also cause Curie point shift and the sign of ∆T am C is also composition dependent.…”

Section: T Am C Shift Caused By Low Temperature Store Of Samples (78 K)mentioning

confidence: 95%

New Approach to the Phenomenology of Amorphous Curie-Point Relaxation

Lovas

2010

Acta Phys. Pol. A

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The possible origin of short range atomic displacements coupled with the irreversible amorphous Curie temperature relaxation (∆T am C ) in Fe-based glasses is discussed and analyzed on the basis of quenched-in phase reminiscences. The displacements are dominantly symmetry changes, which are governed by the relative stability of fcc and bcc quenched-in phase reminiscences at a given temperature range. Those of elements which cause positive ∆T am C in as quenched state, also cause positive irreversible ∆T am C during structural relaxation. The influence of Cr addition is just the opposite in this respect.

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“…The annealing of amorphous magnetic metallic alloys (AMMAs) at temperatures much below the crystallization temperature T c (low-temperature annealing) [1] and cryogenic treatment (CT, some hours of conditioning at liquid-nitrogen temperature [2,3]) lead to a change of the microscopic properties [4]. The relaxation of the microscopic heterogeneity with the change of the short-range topological and chemical order on distances of 0.4-0.7 nm leads probably to the change of the macroscopic properties of AMMAs after the cryogenic treatment [5].…”

Section: Introductionmentioning

confidence: 99%

“…The neutron-diffraction experiments were made at the time-of-flight diffractometer DN-2 [8] and the time-of-flight small-angle-scattering spectrometer YuMO [9] at the IBR-2 reactor of JINR (Dubna, Russia). The dimensions of the sample stack in the neutron beam were 40 × 15 × 0.3 mm 3 . For the smallangle-scattering spectrometer, the samples were placed in a thermostat with a temperature of about 293 K. The experimental results were calculated by the standard SAS scheme [9].…”

Section: Introductionmentioning

confidence: 99%

Neutron‐scattering investigation of Co‐ and Fe‐based amorphous alloys

Dokukin

Beskrovnyĭ

Куклин

et al. 2004

Physica Status Solidi (b)

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8.8 alloys were investigated with a time-of-flight small-angle-scattering spectrometer. Also, a structural factor and a total pair correlation function for the amorphous magnetic metallic alloy Co 66 Fe 4 Si 15 B 15 were obtained using the-neutron diffraction method. It was found that cryogenic treatment of the samples (during some hours of conditioning at liquid-nitrogen temperature) affected only the short-range order up to ~1.5 nm, although lowtemperature annealing at temperatures lower than 670 K leads to structural changes at distances larger than 30 nm. The short-range-order change is explained in the framework of structural relaxation. . The relaxation of the microscopic heterogeneity with the change of the short-range topological and chemical order on distances of 0.4-0.7 nm leads probably to the change of the macroscopic properties of AMMAs after the cryogenic treatment [5]. The amorphous metal contains many defects after quenching. The defects result in the distribution of the atomic density and a certain threshold can be considered as vacancies. Such vacancies, defined as a void, are capable of drifting through the alloy by the exchange of the neighbouring atoms [6]. In the amorphous iron model, the potential for the atom shift into the void has a profile of the activation barrier with the void radius above 80 pm. The sharp cooling of the sample allows us to create non-stationary (excess or "frozen") defects because the defect equilibrium conditions change abruptly with temperature. The large number of the non-equilibrium defects increases a self-diffusion velocity [7].In the present work, the properties of amorphous Co-and Fe-based alloys were investigated with neutron diffraction and small-angle scattering. We also observed structural changes of amorphous Fe-and Co-based alloys after cryogenic treatment and low-temperature annealing.

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Low-temperature irreversible structural relaxation of amorphous metallic alloys

Cited by 26 publications

References 1 publication

Stored energy in metallic glasses due to strains within the elastic limit

Stored energy in metallic glasses due to strains within the elastic limit

New Approach to the Phenomenology of Amorphous Curie-Point Relaxation

Neutron‐scattering investigation of Co‐ and Fe‐based amorphous alloys

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