Zr&amp;ndash;Al&amp;ndash;Ni Amorphous Alloys with High Glass Transition Temperature and Significant Supercooled Liquid Region

Inoue, Akihisa; Zhang, Tao; Masumoto, T.

doi:10.2320/matertrans1989.31.177

Cited by 918 publications

(433 citation statements)

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“…1 Critical cooling rates of monoatomic metallic systems are typically of the order of 10 12 K/s. In contrast, R c of recently discovered multicomponent bulk metallic glass-forming alloys 2,3 is of the order of a few K/s. This excellent glass-forming ability enables investigations of crystallization, 4,5 viscosity, 6 and diffusion 7,8 as well as relaxation 9 in the supercooled liquid region.…”

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confidence: 96%

Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

et al. 1999

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The crystallization behavior of the supercooled bulk metallic glass-forming Zr 41 Ti 14 Cu 12 Ni 10 Be 23 liquid was studied with different heating and cooling rates. A rate of about 1 K/s is sufficient to suppress crystallization of the melt upon cooling from the equilibrium liquid. Upon heating, in contrast, a rate of about 200 K/s is necessary to avoid crystallization. The difference between the critical heating and cooling rate is discussed with respect to diffusion-limited growth taking classical nucleation into account. The calculated asymmetry of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are exposed to different growth rates. ͓S0163-1829͑99͒07441-X͔The ability to form a glass by cooling from the equilibrium liquid is equivalent to suppressing crystallization within the supercooled ͑undercooled͒ liquid. One of the central quantities in theoretical and experimental studies of glass formation is the critical cooling rate R c to bypass crystallization upon cooling from the stable melt. 1 Critical cooling rates of monoatomic metallic systems are typically of the order of 10 12 K/s. In contrast, R c of recently discovered multicomponent bulk metallic glass-forming alloys 2,3 is of the order of a few K/s. This excellent glass-forming ability enables investigations of crystallization, 4,5 viscosity, 6 and diffusion 7,8 as well as relaxation 9 in the supercooled liquid region. The critical cooling rate of Zr 41 Ti 14 Cu 12 Ni 10 Be 23 ͑Vit 1͒, studied in this work, is about 1 K/s. 10 In contrast, crystallization of amorphous Vit 1, previously investigated by differential scanning calorimetry ͑DSC͒ upon heating 11 could not be avoided up to the maximum heating rate of the DSC of 5 K/s and the critical heating rate has not been determined yet. The critical heating rate R h , the counterpart of the critical cooling rate upon heating, is the lowest rate an amorphous sample can be heated through the entire supercooled liquid region without crystallization.In this paper, the onset temperature of crystallization is investigated during cooling from the stable melt and heating amorphous Vit 1 as a function of cooling and heating rate, respectively. For this purpose we designed an experimental setup that permits maximum heating rates of 350 K/s and maximum cooling rates of 40 K/s. We will show that an asymmetry of R c and R h results from the fact that nuclei formed during cooling and heating are exposed to different growth rates, which is likely to be a general feature for metallic systems.The investigations were performed in high-purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk Vit 1 sample. 12 The samples were mounted into the graphite crucibles and inductively heated in vacuum of 10 Ϫ6 mbar or in a titanium-gettered argon atmosphere. The temperature was measured using a thermocouple ͑type K͒ with an accuracy better than Ϯ2 K. Details of the experimental setup can b...

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Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

et al. 1999

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“…'' 5 Recently, a unique family of multicomponent glass forming systems with a high thermal stability and excellent glass forming ability was found. 6,7 The critical cooling rate to form these bulk metallic glasses ͑BMG͒ from the melt drops orders of magnitude compared to conventional metallic glasses. For the particular Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 alloy critical cooling rates as low as 1 K/s were found.…”

Section: P Thiyagarajanmentioning

confidence: 99%

Formation of nanocrystals based on decomposition in the amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy

Schneider¹,

Thiyagarajan²,

Johnson³

1996

Applied Physics Letters

240

123

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22.5 have been studied by small angle neutron scattering ͑SANS͒, transmission electron microscopy ͑TEM͒, and differential scanning calorimetry ͑DSC͒. SANS data of samples annealed isothermally at 623 K exhibit an interference peak centered at qϭ0.46 nm Ϫ1 after an incubation time of about 100 min. TEM and DSC investigations confirm that the respective periodic variation in the scattering length density is due to the formation of nanocrystals embedded in the amorphous matrix. These observations suggest that during the incubation time a chemical decomposition process occurs and the related periodic composition fluctuations give rise to the observed periodic arrangement of the nanocrystals. © 1996 American Institute of Physics. ͓S0003-6951͑96͒04804-2͔In metallic glasses, crystallization and decomposition have been observed in undercooled liquids during cooling from the melt as well as during reheating experiments. [1][2][3] Phase separation requires diffusivity of the atomic species over several interatomic distances and at least two local minima of the Gibbs free energy versus composition function. In multicomponent alloys a large difference in the heat of mixing of the constitutive binary liquids can act as a thermodynamical driving force for phase separation. 4 In these systems the nucleation of crystalline phases is more difficult than for conventional binary metallic glasses, as expressed by the ''Confusion Principle. '' 5 Recently, a unique family of multicomponent glass forming systems with a high thermal stability and excellent glass forming ability was found. 6,7 The critical cooling rate to form these bulk metallic glasses ͑BMG͒ from the melt drops orders of magnitude compared to conventional metallic glasses. For the particular Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 alloy critical cooling rates as low as 1 K/s were found. 8 These low cooling rates allow one to observe phase separation taking place below a miscibility gap in the undercooled liquid region, so that decomposition in the as-prepared amorphous Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 alloy on a length scale of 50-80 nm was observed earlier. 9,10 This decomposition during the cooling process mainly involves the fast diffusion of Be. 11 In this letter, we will show that primary crystallization of the amorphous Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 alloy reheated into the supercooled liquid involves a decomposition process. Phase separation with respect to slower moving species determines the time scale of the primary crystallization in the supercooled liquid. The formation of nanocrystals during isothermal annealing of the Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 alloy has been investigated by small angle neutron scattering ͑SANS͒, transmission electron microscopy ͑TEM͒, and differential scanning calorimetry ͑DSC͒. The results from these studies suggest a decomposition process on a length scale of 13.7 nm preceding the primary crystallization of this alloy when annealed at 623 K.Amorphous samples were prepared from a mixture of the pure elements by...

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“…However, during the last decade, some exceptions have been reported because of the discoveries of stabilized supercooled liquid alloys without crystallization even during cooling at slow rates below 100 K/s [1,2]. As a result, bulk amorphous alloys have been prepared in a number of alloy systems such as Mg- [3], Ln(lanthanide)- [4], Zr- [5,6], Fe- [7], Pd-Cu- [8], Ti- [9], Ni- [10] and Co- [11] bases and have gained some applications due to their unique mechanical properties, chemical properties and good workability resulting from the amorphous structure. It has subsequently been found that the use of the stabilized liquid also gives rise to bulk amorphous alloys containing nanocrystalline [12] and nanoquasicrystalline [13] particles with good mechanical properties in the Zr-based alloy systems.…”

Section: Introductionmentioning

confidence: 99%

High-strength Zr-based bulk amorphous alloys containing nanocrystalline and nanoquasicrystalline particles

Inoue

Fan

Saida

et al. 2000

Science and Technology of Advanced Materials

115

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It was recently found that the addition of special elements leading to the deviation from the three empirical rules for the achievement of high glass-forming ability causes new mixed structures consisting of the amorphous phase containing nanoscale compound or quasicrystal particles in Zr-Al-Ni-Cu-M (M Ag, Pd, Au, Pt or Nb) bulk alloys prepared by the copper mold casting and squeeze casting methods. In addition, the mechanical strength and ductility of the nonequilibrium phase bulk alloys are significantly improved by the formation of the nanostructures as compared with the corresponding amorphous single phase alloys. The composition ranges, formation factors, preparation processes, unique microstructures and improved mechanical properties of the nanocrystalline and nanoquasicrystalline Zr-based bulk alloys are reviewed on the basis of our recent results reported over the last two years. The success of synthesizing the novel nonequilibrium, highstrength bulk alloys with good mechanical properties is significant for the future progress of basic science and engineering. ᭧

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Zr–Al–Ni Amorphous Alloys with High Glass Transition Temperature and Significant Supercooled Liquid Region

Cited by 918 publications

References 9 publications

Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

Formation of nanocrystals based on decomposition in the amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy

High-strength Zr-based bulk amorphous alloys containing nanocrystalline and nanoquasicrystalline particles

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