Continuous refinement of the microstructure during crystallization of supercooled Zr41Ti14Cu12Ni10Be23 melts

Schroers, Jan; Busch, Ralf; Masuhr, Andreas; Johnson, William L.

doi:10.1063/1.124020

Cited by 75 publications

(46 citation statements)

References 15 publications

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“…It is possible that the incubation time preceding quasicrystal formation at low temperatures is directly influenced by such a process. As it has been suggested in several investigations that decomposition is the rate limiting step for crystallization, 22,23 increases in isothermal stability from Vit1͑-b͒ to Vit4 could therefore be attributed to differences in the timescale for decomposition for each alloy. Löffler et al demonstrated the existence of spatially correlated inhomogeneities in Vit1-Vit4 after annealing at various temperatures.…”

Section: Discussionmentioning

confidence: 99%

Timescales of crystallization and viscous flow of the bulk glass-forming Zr-Ti-Ni-Cu-Be alloys

2003

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Crystallization behavior and equilibrium viscosity of a series of alloys in the Zr-Ti-Cu-Ni-Be system are studied using multiple techniques to determine the various contributions to glass-forming ability. Lowtemperature time-temperature-transformation diagrams of alloys whose compositions lie at equally spaced points along the tie line from Zr 38.5 Ti 16.5 Cu 15.25 Ni 9.75 Be 20 to Zr 46.25 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 are measured during isothermal annealing of initially amorphous specimens. Surprisingly, for all investigated alloys, a primary quasicrystalline phase forms at a rate which varies substantially with alloy composition. Subsequent constant heating measurements, x-ray-diffraction patterns obtained after various states of annealing, beam bending viscosity results, and previous thermal analysis are all used to describe the influences on crystallization in this series. The description of both the kinetic and thermodynamic aspects of crystallization allows for an explanation of the crystallization mechanism. In addition, it explains why, in this series, thermal stability is greatest in those alloys with the poorest glass-forming ability. Overall, the investigations reveal that simple criteria like thermal stability or high viscosity fail to predict the glass-forming ability in complex bulk glass-forming systems.

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Section: Discussionmentioning

confidence: 99%

Timescales of crystallization and viscous flow of the bulk glass-forming Zr-Ti-Ni-Cu-Be alloys

2003

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“…4, where the samples were processed without containers, was obtained from samples crystallized in graphite crucibles. 9 This method is more user friendly compared to ESL and has the advantage of a more reliable temperature reading.…”

Section: ͓S0003-6951͑00͒02231-2͔mentioning

confidence: 99%

“…This is in contrast to Vit1, where at least three different primary solidified phases have been found for the different degrees of undercooling. 9 As such, the crystallization kinetics of PCNP seem to be less complicated than that of Vit1, although x-ray …”

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confidence: 99%

Time–temperature–transformation diagram and microstructures of bulk glass forming Pd40Cu30Ni10P20

Löffler¹,

Schroers²,

Johnson³

2000

Applied Physics Letters

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Isothermal crystallization studies were performed on the bulk glass forming alloy Pd 40 Cu 30 Ni 10 P 20 in the undercooled liquid region between the glass transition and liquidus temperature, resulting in a complete time-temperature-transformation ͑TTT͒ diagram for crystallization. The TTT diagram shows a typical ''C'' shape with the nose at 50 s and 680 K. Assuming steady state nucleation and a diffusion-controlled growth rate, the TTT diagram was successfully fit over the entire range of the measurement. The microstructure after isothermal crystallization shows a modulation in Cu and P for all degrees of undercooling. The primary solidified phase is Cu 3 Pd, which forms distinct dendrites at low undercooling. From additional constant cooling experiments, the critical cooling rate to bypass crystallization was determined to be 0. 3 has an excellent glass forming ability that has initiated a series of crystallization studies over a wide temperature range below the melting temperature. A complete time-temperaturetransformation ͑TTT͒ diagram for crystallization was measured by containerless electrostatic levitation ͑ESL͒ over the entire temperature range of the undercooled liquid, i.e., from the melting point down to the glass transition temperature, T g . 4 This TTT diagram showed a typical ''C'' shape with the nose at 51 s and 850 K. The critical cooling rate to bypass crystallization was found to be 1.8 K/s. The TTT diagram could not be described by kinetic formulations as given, for example, by Uhlmann 5 and Davis. 6 This was attributed to the relatively complex crystallization behavior of Vit1, particularly at low temperatures where decomposition precedes nucleation. This method is more user friendly compared to ESL and has the advantage of a more reliable temperature reading.Recently, the new Pd based bulk amorphous glass Pd 40 Cu 30 Ni 10 P 20 ͑PCNP͒ was found, 10 which has a glass forming ability far exceeding that of Pd 40 Ni 40 P 20 and approaching or even exceeding that of Vit1. In contrast to Vit1, this Pd based alloy shows no decomposition on the nanometer scale at temperatures near T g . 11In this letter, we report on crystallization studies of PCNP. Processing this alloy in graphite crucibles, using boron oxide flux, enabled us to measure the complete TTT diagram for crystallization in the undercooled melt and to determine the critical cooling rate. We present results of microstructure analysis of the PCNP melt after crystallization at temperatures near the nose of the TTT diagram. We further give a kinetic formulation which fits the TTT diagram over the entire range of the measurement.Amorphous PCNP was produced by induction melting of Pd, Cu 73.4 P 26.6 , Ni 2 P, and P in a silica tube of 10 mm diameter, using B 2 O 3 oxide flux, and subsequent water quenching. For the crystallization studies, we used a differential thermal analysis ͑DTA͒ setup, 12 equipped with two graphite crucibles. The material was introduced to one of the crucibles, whereas the other was used as a reference. The crucibles w...

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“…In a complex system like Vit 1 an adequate description of the nucleation process will certainly have to go beyond the concept of steady-state nucleation. 5 Further influences such as, for example, decomposition processes, have to be considered [15][16][17] to explain the fine microstructures of Vit 1. 5 At this point, however, to discuss the different growth kinetics on crystallization the simplified approach of steady-state nucleation serves as a sufficient model.…”

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confidence: 99%

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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Continuous refinement of the microstructure during crystallization of supercooled Zr41Ti14Cu12Ni10Be23 melts

Cited by 75 publications

References 15 publications

Timescales of crystallization and viscous flow of the bulk glass-forming Zr-Ti-Ni-Cu-Be alloys

Timescales of crystallization and viscous flow of the bulk glass-forming Zr-Ti-Ni-Cu-Be alloys

Time–temperature–transformation diagram and microstructures of bulk glass forming Pd40Cu30Ni10P20

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

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