Primary crystallization reactions in Al-based metallic glass alloys

Perepezko, John H.; Imhoff, Seth D.

doi:10.1016/j.jallcom.2010.02.063

Cited by 13 publications

(14 citation statements)

References 28 publications

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“…For most of MG systems, the glass transition signal is strong enough to be detected in the heating DSC trace, which makes it possible to measure the glass transition temperature and the supercooled liquid region by normal DSC method. However, for marginal Al‐based MGs, the glass transition signal is prone to be covered by a primary crystallization peak for Al nanocrystals . Thus, the traditional DSC is not a good thermal analysis method to observe the glass transition behaviors of Al‐based MGs.…”

Section: Introductionmentioning

confidence: 99%

Al‐Based Amorphous Metallic Plastics

Gao

Perepezko

2019

Adv Eng Mater

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A new class of Al-based metallic glasses is identified, which exhibits polymerlike thermoplastic formability near the boiling point of water. To satisfy the requirements for thermoplastic behavior, a series of AlSm-based metallic glasses are examined by Flash DSC to determine the glass transition temperature, T g . Viscosity measurements confirm that the T g values of the AlSm-based glasses are below 100 C. Bending and imprinting trials in boiling water demonstrate permanent deformation without the development of shear bands as required for thermoplastic behavior. Comparison of the thermoplastic formability index values indicates that the AlSm-based glasses exhibit behavior similar to that for common Fe-based metallic glasses. Kinetic measurements are used to evaluate the lifetime before the onset of crystallization. The AlSm-based glasses have a significant potential in the areas of electromechanical systems, micro-scale biomedical parts, nanorobots, and micromachines.

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Section: Introductionmentioning

confidence: 99%

Al‐Based Amorphous Metallic Plastics

Gao

Perepezko

2019

Adv Eng Mater

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“…However, for a phase separation within a miscibility gap, the volume fraction of Al-rich regions and the subsequent nucleation density can decrease with increasing crystallization temperature. In contrast, in the few alloy systems where quantitative nucleation rates have been measured, the rate increases with increasing crystallization temperature [10,36,42].…”

Section: Phase Separation Modelmentioning

confidence: 94%

“…In another approach, the details of the nucleation statistics can be obtained from direct TEM observation to determine the Al nanocrystal size distribution as a function of isothermal annealing time and temperature [10,11]. This allows for a direct measurement of the steady state nucleation rate and reveals the importance of transient behavior associated with a delay time τ.…”

Section: Crystallization Behaviormentioning

confidence: 99%

“…Secondly, most of the Al-based metallic glasses exhibit no obvious glass transition signal T g nor the supercooled liquid region in the differential scanning calorimetry (DSC) continuous heating trace because the onset of the primary crystallization peak T x nearly coincides with the glass transition [5]. Other approaches such as the temperature-modulated DSC (TMDSC) and dynamic mechanical analysis (DMA) can be applied to measure T g more precisely [5][6][7][8] and a hold below T x can reveal the T g signal [9,10]. Thirdly, a typical continuous DSC trace for most of the Al-based metallic glass shows a shallow primary crystallization peak for Al fcc followed by sharp secondary crystallization peaks of intermetallic phases ( Fig.…”

Section: Introductionmentioning

confidence: 99%

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Al-based amorphous alloys: Glass-forming ability, crystallization behavior and effects of minor alloying additions

Shen

Perepezko

2017

Journal of Alloys and Compounds

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The main recent advances in Al-based amorphous alloys are discussed in three areas: crystallization behavior, glass-forming ability and minor alloying effects. First, as a brief introduction, the special features and structure-property relationships are presented for the Albased amorphous alloys. The different models for the nucleation behaviors, such as phase separation model and the quenched-in nuclei model, are compared and evaluated. In addition, an overview is given for the effects of minor alloying additions on glass-forming ability (GFA) and the crystallization behavior in terms of the reported structural, thermodynamic, kinetic factors.

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“…Flash DSC has been widely applied to study the melting, crystallization, phase transition and relaxations in various glassy materials, such as the polymers, amorphous alloys and other organic materials (Gao and Perepezko, 2019;Zhuravlev and Schick, 2010). In particular, it has been reported that the observation of an exothermic peak after an observed incubation time during isothermal tests clearly indicates that the nanocrystallization reaction in Al-based MGs is a heterogeneous nucleation and growth mechanism (Perepezko and Imhoff, 2010). What is more, several nanocrystal size distribution analysis studies also showed that there exists an incubation time before the observation of a high number density of nanocrystals, which is consistent with a transient heterogeneous nucleation mechanism (Perepezko, 2004;Shen and Perepezko, 2015;Zhao et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Nanoglass and Nanocrystallization Reactions in Metallic Glasses

2021

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Strategies to change the properties of metallic glass by controlling the crystallization and the glass transition behavior are essential in promoting the application of these materials. Aside from changing the composition approaches to stabilize the glass and frustrate the nucleation and growth of crystals, new strategies at a fixed glass composition are of special interest. In this review, some recent work is summarized on new strategies to tune the properties of metallic glasses without changing composition. First, the nanocrystallization strategy is introduced that is based on the nanocrystallized microstructures such as those that develop in marginal Al-based metallic glasses. The heterogeneous and transient nucleation effects in the nanocrystallization reactions in Al-based metallic glasses are systematically investigated and can be assessed by the determination of delay time based on Flash DSC measurements. These results provide a basis to understand the strong effect of minor alloying additions on the onset of primary Al nanocrystallization and to design the novel Al-based composites with improved properties. Secondly, by an optimal annealing treatment, a liquid-cooled Au-based metallic glass can achieve very high kinetic stability to yield a large increase in glass transition temperature of 28 K and this is 3-5 times larger than the increase usually reported. The measured enthalpy decrease is about 50% of the difference between the as-cooled glass and the equilibrium crystalline state and reaches the extrapolated enthalpy of the supercooled liquid. Finally, the nano-glass strategy makes an Au-based nanoglass show ultrastable kinetic characters at low heating rate (e.g., 300 K/s) compared to a melt-spun ribbon, which is attributed to the kinetic constraint effect of nanoglobular interfaces. These results indicate that the nanoglass microstructure can act to increase metallic glass stability and provide another mechanism for the synthesis of ultrastable glass. These developments open new opportunities to improve the stability and properties and largely increase the application potentials of metallic glasses.

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Primary crystallization reactions in Al-based metallic glass alloys

Cited by 13 publications

References 28 publications

Al‐Based Amorphous Metallic Plastics

Al‐Based Amorphous Metallic Plastics

Al-based amorphous alloys: Glass-forming ability, crystallization behavior and effects of minor alloying additions

Nanoglass and Nanocrystallization Reactions in Metallic Glasses

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