Fragility of superheated melts and glass-forming ability in Pr-based alloys

Meng, Qingguo; Zhou, Jiankun; Zheng, Hongxing; Li, J.G.

doi:10.1016/j.scriptamat.2005.11.023

Cited by 41 publications

(25 citation statements)

References 15 publications

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“…where η 0 is the pre-exponential viscosity, T is the temperature, R is the gas constant (8.314 J/(mol*K)), and E is the activation energy which is the required energy to move flow unit from one balanced position to another one in the melt [20]. The measured data for these alloy melts well obey the Arrhenius equation.…”

Section: Viscosity In the Superheated Liquid Regionmentioning

confidence: 75%

“…In comparison with conventional BMGs, HE-BMGs in the same alloy system usually exhibit higher stability against crystallization upon heating [2]. For example, the Be 20 Cu 20 Ni 20 Ti 20 Zr 20 HE-BMG shows higher activation energy for crystallization (i.e. 281 kJ/mol) and much more sluggish growth of the crystallized phases when compared with its conventional BMG counterpart Vitreloy1 (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Unusual relation between glass-forming ability and thermal stability of high-entropy bulk metallic glasses

Yang

Liu

et al. 2018

Materials Research Letters

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It is generally accepted that good glass formers have a high thermal stability against crystallization upon heating. In this paper, we report an unusual relationship between thermal stability and glass-forming ability (GFA) for high-entropy bulk metallic glasses (HE-BMGs). As compared with their conventional counterparts in the same alloy system, the HE-BMGs have a lower energy barrier for atomic diffusion during undercooling, which facilitates crystallization and then reduces the GFA. Our results clearly demonstrate that the GFA of BMGs is governed by the kinetics of the undercooled liquid, whilst their thermal stability is controlled by atomic diffusion in the glass-transition regime. IMPACT STATEMENTThe undercooled liquid behavior of HE-BMGs plays a key role in determining glass formation, but the thermal stability is controlled by the atomic rearrangement in glassy solid state. ARTICLE HISTORY

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Section: Viscosity In the Superheated Liquid Regionmentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Unusual relation between glass-forming ability and thermal stability of high-entropy bulk metallic glasses

Yang

Liu

et al. 2018

Materials Research Letters

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“…2,3) Rare-earth-based alloys have been investigated due to their unique magnetic properties, complex crystallization behavior, and high amorphous forming ability. [5][6][7][8][9][10][11][12] In particular, the magnetic properties and microstructure of Nd-Fe based alloys have been studied due to their complex microstructure, good magnetic properties, and relation to the Nd-Fe-B permanent magnets by many researchers. Nd-Fe and Pr-Fe amorphous ribbons displayed hard magnetic properties at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Undercooling Solidification and Magnetic Properties of Pr<SUB>90</SUB>Fe<SUB>10</SUB> Alloy Produced by the Gas Flow Levitation Method

2008

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The magnetic properties and amorphous formation ability of Pr-based alloys have been reported and discussed. In this paper, Pr 90 Fe 10 alloys were studied to reveal the solidification behavior associated with undercooling, magnetic properties of the metastable phase, and relation between undercooling and metastable phase formation by using the gas flow levitation method. The samples were solidified at various cooling rates from approximately 50 K/s to approximately 270 K/s. Undercooling increased with the cooling rate. According to the results of the SEM-EDS analysis, the Pr 90 Fe 10 samples that solidified at high undercooling conditions in eutectic reactions consist of the primary -Pr, eutectic -Pr, and metastable phases whereas the samples that solidified at low undercooling conditions in eutectic reactions consist of the primary -Pr, eutectic -Pr, and Pr 2 Fe 17 phases. Additionally, the magnetic properties changed due to the undercooling.

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“…A negative correlation between M and GFA was found in Al-Ni-Ce, Al-Co-Ce and Al-Fe-Ce alloy systems [5]. However, a further study [6,7] found that there is no good relationship between M and GFA in multi-alloy systems including Pr-based, Al-R (rare earth metal) and Al-Co-Ce alloys simultaneously. Al-R and Al-R-M (transition metal) systems are two of the fundamental Al-based amorphous alloy systems [4].…”

mentioning

confidence: 97%

The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

Jia

Bian

Lü

et al. 2010

Sci. China Phys. Mech. Astron.

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The dynamic viscosity of Al-Yb and Al-Ni-Yb superheated melts was measured using a torsional oscillation viscometer. The results show that the temperature dependence of viscosity fits the Arrhenius law well and the fitting factors are calculated. The amorphous ribbons of these alloys were produced by the melt spinning technique and the thermal properties were characterized by using a differential scanning calorimetry (DSC). E (the activation energy for viscous flow), which reflects the change rate of viscosity, has a good negative relation with the GFA in both Al-Yb and Al-Ni-Yb systems. However, there is no direct relation between liquidus viscosity ( L ) and GFA. The superheated fragility M can predict GFA in Al-Yb or Al-Ni-Yb alloy system.Al-based amorphous alloys, glass-forming ability, viscosity, fragility of superheated melt PACS: 81.05. Kf, 66.20.+d From a physical point of view, viscosity is the micro-shear stress for a velocity gradient unit in fluid flow. Probing the viscosity starts a dynamic description of the structure of liquid metals. Thus the viscosity is regarded as a macro-performance of the micro-atomic interaction and is sensitive to the change in the structure [1]. Viscosity is one of the most important factors that affect the glass forming process. It is demonstrated that the three GFA factors, i.e. critical cooling rate R c , the reduced glass transition temperature T rg and supercooled liquid range T x , can be deduced only from the equations of temperature dependence of viscosity [2]. However, the interrelationship between the viscosity behavior of superheated liquid and the GFA of metallic glasses is poorly understood because of the difficulty of viscosity measurement at high temperatures.The concept of fragility m first proposed by Angell [3] is defined as the deviation of temperature dependence of viscosity approaching T g (the glass transition temperature). It is widely used to classify the dynamic behavior of supercooled liquids and glasses. However, for the alloys with low GFA (such as Al-based alloys belonging to marginal glass forming alloys [4]), it is difficult to obtain T g as well as m. Recently a new concept, the fragility of superheated melts M [5] defined as the viscosity variation rate of superheated liquids towards the liquidus temperature, has been proposed by Bian. A negative correlation between M and GFA was found in Al-Ni-Ce, Al-Co-Ce and Al-Fe-Ce alloy systems [5]. However, a further study [6,7] found that there is no good relationship between M and GFA in multi-alloy systems including Pr-based, Al-R (rare earth metal) and Al-Co-Ce alloys simultaneously. Al-R and Al-R-M (transition metal) systems are two of the fundamental Al-based amorphous alloy systems [4]. In order to further clarify the correlation between GFA and M in Al-based metallic glasses, we chose the Al-Yb of Al-R and the corresponding Al-Ni-Yb of Al-R-M alloys in the present work. We measured the viscosity of the melts at high temperatures above liquidus and calculated the fitting factors according...

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Fragility of superheated melts and glass-forming ability in Pr-based alloys

Cited by 41 publications

References 15 publications

Unusual relation between glass-forming ability and thermal stability of high-entropy bulk metallic glasses

Unusual relation between glass-forming ability and thermal stability of high-entropy bulk metallic glasses

Undercooling Solidification and Magnetic Properties of Pr<SUB>90</SUB>Fe<SUB>10</SUB> Alloy Produced by the Gas Flow Levitation Method

The relationship between viscosity and glass forming ability of Al-(Ni)-Yb alloy systems

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