Phase Diagrams and Glass Formation in Metallic Systems

Baricco, Marcello; Palumbo, Mauro

doi:10.1002/adem.200700045

Cited by 13 publications

(4 citation statements)

References 63 publications

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“…Thermodynamic studies of glass transition often emphasizes the liquid−solid Gibbs free energy difference Δ G l→s = Δ H − T Δ S as the thermodynamic driving force to relate to the glass-forming ability of a material, and the relative low Δ G in supercooled liquid regions ( T < T f ) is effective to prevent crystallization and is therefore favorable to glass formation. ,,− The approximation of Δ G l→s ≈ Δ S m Δ T at small supercoolings again highlights the importance of small Δ S m (or dΔ G /d T ) for glass formation because of the small thermodynamic driving force. Entropy, in particular, melting entropy Δ S m , has been experimentally evidenced to play a considerable role in glass formation. − …”

Section: Discussionmentioning

confidence: 99%

“…For binary or multicomponent systems, glass formation from liquid quenching is mainly studied in metallic alloys and inorganic materials such as oxide and chalcogenide glasses. − The systems hold relatively low GFA, and the best GFR might not be easily determined . Molecular systems, in contrast, have higher GFA and favor the studies of glass formation with regards to phase diagram.…”

Section: Introductionmentioning

confidence: 99%

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Glass Transition in Binary Eutectic Systems: Best Glass-Forming Composition

Wang

Chen

et al. 2010

J. Phys. Chem. B

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The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Glass Transition in Binary Eutectic Systems: Best Glass-Forming Composition

Wang

Chen

et al. 2010

J. Phys. Chem. B

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“…As reported in the literature, the glass-forming capability of an alloy is highest near the eutectic composition at a low melting eutectic. [10] Glass formation in these alloys is also possible at eutectic composition since several phases are formed and the diffusion ways are long.…”

Section: Resultsmentioning

confidence: 99%

Crystallization Behaviour of Amorphous Mg‐Zn‐Al‐Alloys

et al. 2008

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Since the importance of magnesium alloys has increased during recent years there is an intense need for appropriate joining technologies. This concerns the joining of both similar and dissimilar materials (such as magnesium and aluminium, for instance). Welding technologies offer a broad range of joining parameters, [1] but they are not appropriate, in most of the cases, for joining highly alloyed materials and joining dissimilar materials. Only beam welding and friction welding can be used for joining dissimilar materials. [2] The main drawback of welding processes is the high temperature load of the base materials. Mechanical joining can cause corrosion problems if ferrous joining elements are used, for instance. Thus, alternative low-heat joining technologies for joining magnesium alloys both to each other and to aluminum alloys are examined in the present study.Appropriate filler materials for soldering magnesium are not available. Therefore, new filler metals have to be developed. Zn-Mg-Al based alloys offer a high potential since they possess a low electrochemical difference in comparison to the magnesium based material, on one hand. On the other hand, they are well suited from the metallurgical point of view. Soldering temperatures are about 350°C. Thus, the filler materials can be applied to many of the magnesium-based alloys.Amorphous magnesium-based alloys were investigated already during several studies. e.g. [3][4][5][6] The aim was to get better mechanical properties in comparison to crystalline magnesium alloys. It was found that the crystallization behaviour depends very strongly on the amount of additional alloying elements.The filler metals are produced as amorphous tapes, since solidification at non-equilibrium conditions results in a new structure and, thus, the mechanical properties are completely different. Since amorphous filler tapes are very elastic they have been known for a long time to be much easier to handle during the application to the soldering gap than are crystalline filler metals are. Having a defined thickness, the tapes offer an additional advantage since the soldering or brazing gap can be adjusted very easily. [7] The production of amorphous tapes is already common for nickel based or copper based filler metals, for instance. It has been shown [8] that the use of amorphous filler materials results in finer microstructures and a minimization of intermetallic phases after soldering in comparison to the use of crystalline fillers. Another advantage of amorphous filler metals is that they posses very good homogeneity. Experimental ProcedureA filler alloy composition containing 55 mass-% Zn, 42 % Mg, and 3 % Al was produced by continuous casting using an S8-midi machine (Frisch GmbH). The alloys were induction heated to a temperature of 650°C and afterwards directly casted into a cylindrical die. Argon was used as a protective gas during the whole process. The rods have a diameter of 14 mm. The elemental composition was examined using electron diffraction X-ray spectroscopy (EDXS...

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“…Eutectic systems formed by water with various organic and inorganic compounds are more prone to vitrification than pure compounds. , One of the characteristics of systems with the glass-forming ability is the glass-forming region (GFR), that is , the composition range where the crystallization of components can be circumvented by adjusting the cooling rate. However, for many systems the prediction of GFR is challenging, − especially for mixtures of molecular compounds, studied less extensively than metal alloys and inorganic solutions. − For the latter mixtures, Rawson’s law was formed, stating that vitrification occurs at the eutectic point. However, it was shown for many mixtures that the GFR extends to compositions considerably different from those at the eutectic point. − Also, depending on the system, the time scale of glass–crystal transformations can considerably vary .…”

Section: Introductionmentioning

confidence: 99%

Vitrification and New Phases in the Water:Pyrimidine Binary Eutectic System

et al. 2019

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The binary diagram for pyrimidine:water mixtures has been determined by differential scanning calorimetry, in situ single-crystal, and powder X-ray diffraction experiments. The eutectic point has been located near the 1:4 n/n ratio at 234.5 K. The eutectic and nearly eutectic mixtures easily vitrify, and the vitrification could be kinetically induced for 1:3 n/n mixtures, too. Depending on the cooling rate, the 1:4 mixture freezes in the glass state, as a conglomerate of the glass and crystalline phases, or as the eutectic mixture of pyrimidine phase I and hexagonal ice I h . When heated above 160 K, the glass phase transforms to a novel crystalline phase, tentatively identified as a pyrimidine hydrate, which in turn at ca. 200−210 K transforms into a eutectic mixture of pyrimidine phase I and hexagonal ice I h . The pyrimidine−water binary diagram and novel crystalline and amorphous phases are relevant to the thermodynamic behavior of hydrophilic pyrimidine and its natural and synthetic derivatives in humid environments. The presently determined binary diagram can be straightforwardly applied for assessing the contents of water in highly hygroscopic pyrimidine samples.

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Phase Diagrams and Glass Formation in Metallic Systems

Cited by 13 publications

References 63 publications

Glass Transition in Binary Eutectic Systems: Best Glass-Forming Composition

Glass Transition in Binary Eutectic Systems: Best Glass-Forming Composition

Crystallization Behaviour of Amorphous Mg‐Zn‐Al‐Alloys

Vitrification and New Phases in the Water:Pyrimidine Binary Eutectic System

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