Two-step relaxations in metallic glasses during isothermal annealing

Song, Lijian; Xu, Wei; Huo, Juntao; Wang, Junqiang; Wang, Xinmin; Li, Run-Wei

doi:10.1016/j.intermet.2017.11.016

Cited by 49 publications

(23 citation statements)

References 55 publications

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“…Similar observation of sub- T g enthalpy-recovery peaks is also reported for non-crystallizable polymers including poly (vinyl chloride) [ 75 ], polyarylate, polysulfone, and polycarbonate [ 76 ], bulk [ 77 ] and thin films of polystyrene [ 78 , 79 ], all discussed as presence of a different relaxation mechanism [ 80 ]. However, sub- T g -enthalpy-recovery peaks/presence of different relaxation mechanisms were also detected for metallic glasses [ 81 , 82 , 83 , 84 , 85 ], and small organic molecules, which form orientationally disordered crystals [ 86 ]. Though not being evidence, the frequent detection of annealing-caused endothermic sub- T g peaks in non-crystallizable polymers [ 75 , 76 , 77 , 78 , 79 ] suggests that such peaks may not necessarily be associated to crystallization.…”

Section: Resultsmentioning

confidence: 99%

Enthalpy Relaxation of Polyamide 11 of Different Morphology Far Below the Glass Transition Temperature

Androsch

Jariyavidyanont

Schick

2019

Entropy

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Polyamide 11 (PA 11) samples of different supermolecular structure, including the crystal-free glass and semi-crystalline PA 11 of largely different semi-crystalline morphology, were prepared by fast scanning chip calorimetry (FSC). These samples were then annealed at different temperatures well below the glass transition temperature Tg. The main purpose of the low-temperature annealing experiments was the calorimetric detection of mobility of chain segments at temperatures as low as −40 °C (≈Tg − 80 K) where still excellent impact resistance is predicted. It was found that annealing PA 11 at such low temperature, regardless the thermal history and supermolecular structure including crystallinity as well as crystal shape and size, permits distinct enthalpy relaxation at rather short time scale with the structural changes reverting on subsequent heating as detected with pronounced sub-Tg-enthalpy-recovery peaks. The main glass transition, associated to large-amplitude segmental mobility, as well as relaxations at temperatures only slightly below Tg are even more distinctly sensitive to the crystal morphology. In contrast to spherulitically grown lamellar crystals, presence of high-specific-surface area nanometer-sized ordered domains causes a shift of the glass transition temperature of the amorphous phase to higher temperature, proving stronger coupling of ordered and amorphous phases than in case of lamellae. In addition, the increased coupling of the crystalline and amorphous phases slows down the cooperative rearrangements on annealing the glass slightly below Tg. The performed study contributes to further understanding of the spectrum of structural relaxations in PA 11 including the effect of presence of crystals. Enthalpy relaxation and consequently the reduction of entropy at temperatures slightly below Tg strongly depends on the semi-crystalline morphology, while an only minor effect is seen on low-temperature annealing at Tg − 80 K, possibly indicating different molecular mechanisms for the processes occurring in both temperature ranges. The low-temperature process even seems proceeding in the crystalline fraction of the material.

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Section: Resultsmentioning

confidence: 99%

Enthalpy Relaxation of Polyamide 11 of Different Morphology Far Below the Glass Transition Temperature

Androsch

Jariyavidyanont

Schick

2019

Entropy

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“…This result suggests that the origin of complex aging behavior must be based on a framework disregarding the chemical details of the glass. Indeed, the presence of a fast mechanism of equilibrium recovery has been encountered on the base of a variety of observations in a wide range of system, including bulk metallic glasses [ 21 , 22 , 29 , 32 , 65 , 66 , 67 ], phase change materials [ 68 ], a plastic crystal [ 28 ], chalcogenide glasses [ 19 ], and a low molecular weight glass former [ 20 ]. Although glass-former specific approaches are of interests [ 25 ], these results calls for a universal description.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, experiments by differential scanning calorimetry (DSC)-where the evolution of the enthalpy of the glass is monitored-showed that, if physical aging is conducted considerably below T g and for aging times as long as about one year, two steps in the approach to equilibrium of the enthalpy, each characterized by the attainment of a plateau, are observed for different polymers [18]. This event was shown independently in other glasses, including chalcogenides [19], a small molecule [20], metallic glasses [21,22], and polysulfone [23]; and variously modeled according to different approaches [24][25][26]. Furthermore, if aging is conducted far below T g , prolonged aging results in the attainment of partial recovery of equilibrium even though a plateau in the enthalpy is achieved [27].…”

Section: Introductionmentioning

confidence: 98%

Physical Aging Behavior of a Glassy Polyether

et al. 2021

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The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

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“… [9] revealed the feasibility of this procedure for polymeric materials. Chip calorimetry was used to determine the fragility in lanthanum (La) based metallic glasses using the heating rate dependence of T g [15] and in gold based (Au) metallic glasses [ 16 , 17 ]. In the present work we demonstrate the power of fast chip calorimetry (fast differential scanning calorimetry, FDSC) in determining the calorimetric fragility index of metallic glasses using shifts in the fictive temperature.…”

Section: Introductionmentioning

confidence: 99%

Fast and direct determination of fragility in metallic glasses using chip calorimetry

Spieckermann

Steffny

Bian

et al. 2019

Heliyon

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We directly determine the thermodynamic fragility index of two metallic glasses (Mg65Cu25Gd10 and Au49Cu26.9Si16.3Ag5.5Pd2.3) from fictive temperature shifts induced by a variation of the quenching rate using fast differential scanning calorimetry (FDSC). Recent chip calorimeters are able to achieve the cooling rates necessary to perform such an evaluation. For the Mg65Cu25Gd10 and Au49Cu26.9Si16.3Ag5.5Pd2.3 metallic glasses studied, we find very good agreement of the kinetic fragility index with literature data obtained by conventional calorimetry and rheology. The thermodynamic fragility indices are m=25.5 ± 1.5 for Mg65Cu25Gd10 and m=50.3 ± 2.3 for Au49Cu26.9Si16.3Ag5.5Pd2.3, respectively. The FDSC method discussed here allows for fast and reliable determination of the kinetic fragility of metallic glasses, and is thus competitive with high-frequency methods.

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Two-step relaxations in metallic glasses during isothermal annealing

Cited by 49 publications

References 55 publications

Enthalpy Relaxation of Polyamide 11 of Different Morphology Far Below the Glass Transition Temperature

Enthalpy Relaxation of Polyamide 11 of Different Morphology Far Below the Glass Transition Temperature

Physical Aging Behavior of a Glassy Polyether

Fast and direct determination of fragility in metallic glasses using chip calorimetry

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