Metastable States of Alloys

Cahn, Robert W.; Greer, A.L.

doi:10.1016/b978-044489875-3/50024-7

Cited by 43 publications

(21 citation statements)

References 273 publications

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“…The focus of this issue of MRS Bulletin is on glasses strictly defined in this way, although it should be noted that glasses are but one category of noncrystalline (or amorphous) solids, which in general can be prepared by a variety of methods. 1 The best known natural glass is obsidian, formed by solidification after volcanic activity. The capability to work obsidian to create extremely sharp cutting edges for knives, spears, and arrowheads made this glass attractive to early humans.…”

Section: Introductionmentioning

confidence: 99%

Bulk Metallic Glasses: At the Cutting Edge of Metals Research

Greer¹,

Ma²

2007

MRS Bull.

541

243

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Glassy alloys (metallic glasses) are currently the focus of intense research in the international metals community. Setting aside elevated-temperature applications, these amorphous metals have exciting potential for structural applications. When metallic glasses were first widely studied in the 1960s, the alloy compositions then known to be quenchable into the glassy state from the liquid required high cooling rates on the order of 10 6 K s −1 and were consequently restricted to thin sections. The current interest in metallic glasses has its origin mainly in the increasing range of compositions that can now be cast into glasses at much lower cooling rates, permitting minimum sections of 1 mm to 1 cm or even larger. These bulk metallic glasses (BMGs) are the focus of the articles in this issue of MRS Bulletin. Our goal is to illustrate the major materials issues for BMGs, from processing to structures to properties and from the fundamental science of glasses to viable industrial applications. We hope that the articles, in providing a snapshot of a rapidly moving field, show why BMGs are attracting such intense interest and serve to highlight some challenging issues awaiting resolution.

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Section: Introductionmentioning

confidence: 99%

Bulk Metallic Glasses: At the Cutting Edge of Metals Research

Greer¹,

Ma²

2007

MRS Bull.

541

243

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“…As mentioned by Badrinarayanan et al [95], the fictive temperature correlates with the structural state of a glass, and can be measured upon heating, whereas the glass transition temperature (Tg) is strictly measured on cooling. However, as clearly shown in their work [95], Tf is only about 1.5 °C lower than Tg and thus, the two are practically the same and both depend on the imposed cooling rate [95,96]. Certainly, the calorimetric Tg measured upon heating in a differential scanning calorimeter (DSC) can be safely taken to be Tf.…”

Section: Toughness and The Critical Fictive Temperaturementioning

confidence: 98%

“…Certainly, the calorimetric Tg measured upon heating in a differential scanning calorimeter (DSC) can be safely taken to be Tf. Faster cooling of the undercooled liquid leads to a higher Tg and a higher fraction of free volume [96]. More slowly cooled alloys possess a lower Tg and the glass so obtained is more structurally relaxed, i.e., has less fraction of free volume.…”

Section: Toughness and The Critical Fictive Temperaturementioning

confidence: 99%

Toughness of Bulk Metallic Glasses

Madge

2015

Metals

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Bulk metallic glasses (BMGs) have desirable properties like high strength and low modulus, but their toughness can show much variation, depending on the kind of test as well as alloy chemistry. This article reviews the type of toughness tests commonly performed and the factors influencing the data obtained. It appears that even the less-tough metallic glasses are tougher than oxide glasses. The current theories describing the links between toughness and material parameters, including elastic constants and alloy chemistry (ordering in the glass), are discussed. Based on the current literature, a few important issues for further work are identified.

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“…ball milling. [23] As an additional route (iv) amorphization by high energy radiation [24] is also possible. While the solidification process [9,12,25,26] can directly produce bulk specimens, the powders and flakes that are obtained from the powder metallurgical route [27,28] have to be consolidated in a subsequent step.…”

Section: Processing and Microstructuresmentioning

confidence: 99%

“…The fracture energy can be obtained from Charpy impact tests or can be calculated from the fracture toughness and depends on the alloy composition: [109,[116][117][118][119] Zr-, Cu-, as well as some Fe-and Pt-base BMGs exhibit fracture energies between 60 and 90 kJ/m 2 , whereas Mg-, Ceand some Fe-base BMG have fracture energies below 10 kJ/m 2 . [117] Figure 9 shows the variation of fracture energy of (i) a La 62 Al 14 (Cu,Ni) 24 BMG composite with volume fraction of quenched-in dendritic crystals [107] and of (ii) a La 55 Al 25 Cu 10 Ni 5 Co 5 BMG composite with volume fraction of crystals obtained by partial devitrification. [120] The impact toughness for the monolithic La 62 Al 14 (Cu,Ni) 24 [107] and La 55 Al 25 Cu 10 Ni 5 Co 5 [120] BMGs are 17 kJ/m 2 and 9.43 kJ/m 2 , respectively and the values are normalized with respect to the highest value measured.…”

Section: Fracture Energymentioning

confidence: 99%

Processing Routes, Microstructure and Mechanical Properties of Metallic Glasses and their Composites

et al. 2007

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443Metallic glasses represent an interesting group of materials as they are superior in certain mechanical properties, i.e. they reach near theoretical strength, exhibit large elastic strain (2 %) and low elastic modulus compared to their crystalline counterparts. The discovery of new alloy compositions solidifying into bulk glassy samples allows for conventional mechanical characterization and raises the hope for possible applications as structural material. In order to improve and tailor the mechanical properties, composite materials have been developed that consist of a glassy matrix with second phase dispersions of different chemical compositions, morphology, and different length scale. This article reviews the different processing routes, the evolution of different microstructures and the resulting elastic and plastic properties of metallic glasses and their composites. Additionally, the recently reported monolithic ductile bulk metallic glasses will be discussed in terms of their structure, chemical composition and their unique "work hardening"-like behavior.

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Metastable States of Alloys

Cited by 43 publications

References 273 publications

Bulk Metallic Glasses: At the Cutting Edge of Metals Research

Bulk Metallic Glasses: At the Cutting Edge of Metals Research

Toughness of Bulk Metallic Glasses

Processing Routes, Microstructure and Mechanical Properties of Metallic Glasses and their Composites

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