Newtonian and non-Newtonian viscosity of supercooled liquid in metallic glasses

Kawamura, Y.; Nakamura, Toshihiro; Kato, Hidemi; Mano, Hideo; Inoue, Akihisa

doi:10.1016/s0921-5093(00)01562-8

Cited by 101 publications

(65 citation statements)

References 19 publications

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“…[21][22][23][24][25][26][27][28][29][30] These studies have revealed that the metallic glass forming liquids exhibit intermediate values of the fragility. In the present section the temperature dependence of the viscosity of some metallic glass forming liquids is analyzed in the light of our model.…”

Section: Application To Metallic Glass Forming Liquidsmentioning

confidence: 99%

A Model for the Fragility of Metallic Glass Forming Liquids

Aniya

Shinkawa

2007

Mater. Trans.

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An expression for the temperature dependence of the viscosity and fragility is derived based on a simple model of the melt. According to the model, the fragility is determined by the relaxation of structural units that form the melt, and is described in terms of the bond strength, coordination number, and their fluctuations of the structural units. It is shown that the fragility of some metallic glass forming liquids such as Pd 40 Ni 40 P 20 , La 55 Al 25 Ni 20 and Zr 65 Al 10 Ni 10 Cu 15 are quite well reproduced by the model. The application of the theory to La 55 Al 25 Ni 20 has revealed that the fluctuation in the bond strength between the structural units is about 6% and that the viscous flow occurs when the bonds in about 8 adjoining structural units are broken.

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Section: Application To Metallic Glass Forming Liquidsmentioning

confidence: 99%

A Model for the Fragility of Metallic Glass Forming Liquids

Aniya

Shinkawa

2007

Mater. Trans.

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“…As examples, Fig. 8 shows the X-ray diffraction patterns of Fe 70 Nb 10 B 20 and Fe 60 Nb 10 B 30 glassy alloys that have been subjected to annealing so as to precipitate the primary crystalline phase, together with the data on an amorphous Fe 80 Nb 10 B 10 alloy. 45) The diffraction peaks are identified as the Fe 23 B 6 phase for the two glassy alloys and the precipitation phase is independent of B content in the range from 20 to 30 at%B, leading to the formation of the glassy phase.…”

Section: Bulk Glassy Alloy Systemsmentioning

confidence: 99%

“…1. In any event, all the bulk glassy alloys have a supercooled liquid region with a temperature interval ranging from 40 to 130 K. Figure 23 shows the relation between stress and strain rate at different temperatures including the supercooled liquid region for Zr 65 79,80) Although the viscosity in the temperature range below T g decreases almost linearly with increasing strain rate, the viscosity in the supercooled liquid region remains constant in the low strain rate range, indicating that controlling deformation temperature and strain rate in the supercooled liquid region generate an ideal Newtonian flow for bulk glassy alloys. Under the deformation condition where Newtonian flow is obtained, we have also shown that a linear relation exists between true stress and strain rate and the slope corresponding to the strain rate sensitivity exponent (m-value) is found to be 1.0.…”

Section: Working and Welding In The Supercooled Liquid Regionmentioning

confidence: 99%

Recent Progress in Bulk Glassy Alloys

2002

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This paper deals with recent progress in stabilized supercooled liquid and the resulting bulk glassy alloys and focusing on the following factors; alloy composition, forming ability, formation mechanism, computed glass-forming ability, computed glass formation range, atomic configuration, production techniques, mechanical properties, corrosion resistance, soft magnetic properties, micro-forming ability, applications, significance to science and engineering, and future trends for bulk glassy alloys including supercooled liquid. As demonstrated in this review, the high stability of metallic supercooled liquid has already opened up new fields of investigation in basic science and yielded new engineering applications. There is every reason to expect that their importance will continue to increase.

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“…Plots of the flow stress (lnr) as a function of strain rate (lne) at different temperatures are shown in Figure 7. The strain rate sensitivity exponent (m), which approached 1.0, can be obtained from the slope of the curve for the Mg 58 Cu 31 Y 6 Nd 5 BMG deformed at 448, 453, and 458 K. Considering that the m value is usually below 0.6 for superplastic crystalline alloys, [27] the Mg 58 Cu 31 Y 6 Nd 5 BMG possesses an ideal superplasticity like that of a Newtonian fluid. To prove the excellent workability in the SCL region of the Mg 58 Cu 31 Y 6 Nd 5 BMG, a BMG rod with diameter of 6 mm was extruded into a long wire with diameter of 1 mm for more than 160 mm in length at 458 K. Moreover, a microscaled hologram was fabricated by hot pressing the Mg 58 Cu 31 Y 6 Nd 5 BMG from a pre-engraved 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 die (with microscaled groove) at 458 K in the supercooled iquid region, as shown in Figure 9(a).…”

Section: Resultsmentioning

confidence: 99%

Thermoplastic Forming Properties and Microreplication Ability of a Magnesium‐Based Bulk Metallic Glass

et al. 2008

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The thermoplastic forming properties in the supercooled liquid region of Mg 58 Cu 31 Nd 5 Y 6 bulk metallic glass (BMG) rods were systematically characterized by thermal mechanical analysis (TMA) and compressive tests at different temperature with various strain rates. The process window of thermoplastic forming for the Mg 58 Cu 31 Nd 5 Y 6 BMG was developed according to the results of TMA and the compressive tests. All evidence reveals that the Mg 58 Cu5 31 Nd 5 Y 6 BMG possesses excellent superplastic formability with the m value being nearly 1.0 in the supercooled liquid region of 430-503 K under a strain rate around 2.5 × 10 -3 -1.0 × 10 -2 s -1 . In parallel, a relatively low flow stress (less than 10 MPa) within the supercooled liquid region can be obtained with a strain rate of 2.5 × 10 -3 s -1 . Additionally, the replication of a hologram pattern with 100 nm depth also demonstrates extremely good microforming ability of this Mg-based BMG in the supercooled liquid region.Magnesium alloys have attracted great attention in the category of engineering materials in recent years because of their high specific strength/density ratio and high damping capacity. [1][2][3] However, the inherent of low stiffness and poor workability of conventional magnesium alloys has resulted in its limited application up to now. Therefore, the development of high specific strength Mg-based bulk metallic glasses (BMGs) for application as structural materials is an important research topic. Recently, Inoue et al. [4,5] first found that Mg-Cu-Y ternary alloys exhibited high glass-forming ability (GFA) and can be produced as a BMG rod with a diameter of 7 mm by using copper mold-casting and high-pressure diecasting methods. Moreover, further improvement of the GFA has been reported by partially replacing Cu with a TM (TM: transition metal such as Ag, Pd, or Zn) in the Mg-Cu-Y alloy system, for example, Mg 65 Cu 15 Ag 10 Y 10 , [6,7] Mg 65 Cu 20 Zn 5 Y 10 , [8] and Mg 65 Cu 15 Ag 5 Pd 5 Y 10 . [9,10] Additionally, the significant improvement of their GFA has been reported by adding a rareearth element (Gd, Nd, Tb, Pr, or Dy) and lowering the amount of Mg in the Mg-based amorphous materials, such as Mg-Cu-Y-Gd, [11,12] Mg-Cu-Ni-Gd, [13] Mg-Cu-RE (RE = rareearth element), [14] Mg 54 Cu 28.5 Ag 8.5 Gd 11 , [15] Mg-Cu-GdNd, [16,17] and Mg-Cu-Y-Nd [18] alloy systems. All of these Mg-based BMGs exhibit high compressive fracture strength over 800 MPa, [19][20][21] which is twice the highest strength of conventional Mg-based crystalline alloys. In addition, these Mg-based BMGs usually present significant plasticity in supercooled liquid region (SCL) with behavior similar to a Newtonian viscosity of conventional glass materials, that is, the strain rate sensitivity exponent (m) is near 1. Hence, because of the superplastic deformation ability in the SCL region, Mg-based BMGs are capable of being manufactured into near-net-shape components, particularly for complexshaped microcomponents for micro-electromechanical systems (MEMS). [22][23][24][25...

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Newtonian and non-Newtonian viscosity of supercooled liquid in metallic glasses

Cited by 101 publications

References 19 publications

A Model for the Fragility of Metallic Glass Forming Liquids

A Model for the Fragility of Metallic Glass Forming Liquids

Recent Progress in Bulk Glassy Alloys

Thermoplastic Forming Properties and Microreplication Ability of a Magnesium‐Based Bulk Metallic Glass

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