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Metallic Glasses

Title: "Compositional dependence on phase selection during devitrification of amorphous Zr-Pt alloys"

Authors: M.H. Lee, R.T. Ott, M.F. Besser, M.J. Kramer, and D. J. Sordelet

Contact:  M.H. Lee

Journal:  Scripta Mater. (2006) 55, 505-508.

Abstract:

The devitrification pathways of alloys were determined using time-resolved synchrotron radiation. Amorphous Zr73Pt27 ribbons transformed directly to the stable Zr5Pt3 structure but ribbons with higher Zr contents first formed a metastable quasicrystalline phase before transforming to the Zr5Pt3 structure. Lower crystallization activation energies were observed for the higher Zr-content alloys.

Title: "Glass formation and crystallization in binary Zr-Pt systems"

Authors: M.H. Lee, X. Yang, M.J. Kramer, and D.J. Sordelet

Contact:  M.H. Lee

Journal:  Philos. Mag. (2006) 86, 443-449.

Abstract:

Previous rapid solidification studies of Zr-Pt alloys have focused primarily on compositions very close to the Zr80Pt20 eutectic. In the current work, a wide range of alloys, ZrxPt100-x

(69 ≤ x ≤ 81), were synthesized by melt spinning to examine their starting structures and devitrification behaviors. Similar to the frequently reported formation of a metastable quasicrystalline phase during heating of near-eutectic compositions, ribbons with Zr contents as low as 75at.% show comparable transformations, but at higher temperatures, before transforming to the stable Zr5Pt3 structure. With the quench rate used in this study, a further decrease below 75at.% Zr precludes the formation of the metastable quasicrystalline phase and instead results in crystallization directly to the stable Zr5Pt3 structure. Preliminary analysis of the transformation kinetics reveals a lower activation energy for the transformation of an amorphous Zr-Pt structure to the metastable quasicrystal phase in comparison to the stable Zr5Pt3 phase.

Title: "Quasicrystal formation in Zr-Cu-Ni-Al-Ta metallic glasses and composites"

Authors: R.T. Ott, M.J. Kramer, M.F. Besser, T.C. Hufnagel, and D.J. Sordelet

Contact:  R.T. Ott

Journal:  Philos. Mag. (2006) 86, 299-307.

Abstract:

We have examined the crystallization behavior of Zr-Cu-Ni-Al-Ta metallic glasses and metallic-glass-matrix composites. Monolithic and composite alloys were prepared by varying the amount of Ta added to a Zr-based glass-forming alloy. We find that additions as low as 2 at. % Ta promotes the formation of the icosahedral phase during devitrification, which in turn has a significant effect on the subsequent crystallization behavior. The DSC and time-resolved X-ray scattering results show that following the nucleation of the quasicrystals the alloys exhibit an exothermic event that does not correspond to any discernible structural change. We discuss the possible mechanisms for the second exotherm.

Title: "Influence of Pd on formation of amorphous and quasicrystal phases in rapidly quenched Zr2Cu(1-x)Pdx"

Authors: M. Xu, Y. Ye, J.R. Morris, D.J. Sordelet, and M.J. Kramer

Contact:  M.J. Kramer

Journal:  Philos. Mag. (2006) 86, 389-395.

Abstract:

The role of Pd in the transformation from an amorphous state to a metastable icosahedral quasicrystalline phase in Zr2Cu(1-x)Pdx (x=0 to 1) metallic glasses was investigated using high-energy synchrotron X-rays and differential scanning calorimetry. The total scattering functions show an increasing development of the high-Q side of the second diffuse scattering peak at 5.09 Å-1 with increasing Pd content. The reduced radial distribution functions reveals that the bonding distance of the Zr-(Pd/Cu) pairs increases from 2.76 to 2.82 Å when x increases from 0.00 to 1.00, while the distance for the Zr-Zr pairs remains almost const. at 3.10 Å. Thermal analysis and X-ray diffraction together show that an amorphous-to-quasicrystal phase transition is not observed in the Zr2Cu alloy, but partial or total substitution of Cu by Pd in Zr2Cu(1-x)Pdx alloys does lead to quasicrystal formation.

Title: "Quasicrystal formation in mechanically alloyed Zr-Ti-Nb-Cu-Ni-Al glassy powders"

Authors: S. Scudino, C. Mickel, L. Schultz, J. Eckert, X.Y. Yang, and D.J. Sordelet

Contact: D.J. Sordelet

Journal: Appl. Phys. Lett. (2004) 85, 4349-4351.

Abstract:
Different from the glassy Zr62Ti7.07Nb2.21Cu12.28Ni9.81Al6.62 melt-spun ribbon that forms a quasicrystalline phase upon devitrification, the corresponding alloy produced by mechanical alloying of elemental powder mixtures does not clearly show quasicrystal formation. However, the addition of an appropriate amount of elemental zirconium to the mechanical alloyed powder changes the crystallization behavior inducing the formation of an icosahedral quasicrystalline phase as the first crystallization product. This indicates that for this multicomponent metallic glass quasicrystal formation in the mechanical alloyed powder is crucially linked to the composition rather than to the question whether there is a special quenched-in short-range order.

Title: "Meta-stable quasicrystal formation in vitrified and solid state synthesized amorphous Zr-based alloys"

Authors: D.J. Sordelet, E. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: J. Non-Cryst. Solids (2004) 334-335, 263-269.

Abstract:
Amorphous Zr70Pd30, Zr70Pd20Cu10, Zr80Pt20, Zr70Pt20Cu10, and Zr57Ti8Nb2.5Cu3.9Ni1.1Al7.5 alloys were prepared by melt spinning and mechanical milling to compare their devitrification behaviors. The melt-spun ribbons transform from an amorphous structure to a meta-stable quasicrystalline phase. This amorphous-to-quasicrystalline transition is not observed in amorphous powders obtained by mechanical milling. Since the mechanical milling process does not involve direct liquid phase formation of an amorphous structure, it is inferred that in the absence of the short-range order obtained directly from the liquid, meta-stable quasicrystalline phase formation is not energetically favored in these Zr-based metallic glasses.

Title: "Effects of oxygen on meta-stable phase formation in Zr80Pt20 melt spun ribbons"

Authors: D. Sordelet, X. Yang, E. Rozhkova, M. Besser, and M. Kramer

Contact: D.J. Sordelet

Journal: Mater. Res. Soc. Symp. Proc. (2004) 805, 21-27.

Abstract:
This report continues previous studies that show melt spun Zr80Pt20 ribbons having oxygen contents ranging from <200 to approximately 5000 mass ppm form various meta-stable phases during quenching. In the presence of sufficient oxygen, a big cube Zr6Pt30 phase forms, but this structure is de-stabilized towards an icosahedral quasicrystalline structure at lower oxygen levels. Further reduction of oxygen promotes increasingly stable Zr-Pt bonds, and a meta-stable b-Zr(Pt) structure is formed.

Title: "Influence of oxygen content in phase selection during quenching of Zr80Pt20 melt spun ribbons"

Authors: D.J. Sordelet, X. Yang, E.A. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: Intermetallics (2004) 12, 1211-1217.

Abstract:
Depending on processing conditions Zr80Pt20 alloys may form meta-stable quasicrystals either during devitrification of an amorphous phase or directly upon cooling from a liquid. This study reveals that oxygen content during melt spinning indeed strongly influences the formation of the as-quenched structure in this alloy system. At a wheel speed of 25 m/s, a critical amount of oxygen was found to be required to form amorphous ribbons. At lower oxygen levels (i.e. <500 ppm mass), a fully crystallized structure forms that is composed mainly of meta-stable b-Zr with a small fraction of a quasicrystals (QC) phase. At higher oxygen levels (approximately 1000 ppm mass), the as-quenched structure transitions to an apparently amorphous structure, and with further oxygen additions forms a mixture of amorphous and either a QC phase (approximately 1500 ppm mass) or a crystalline Zr6Pt3O phase (>2500 ppm mass). Details regarding the structural similarity between the QC, b-Zr and Zr6Pt3O phases are discussed.

Title: "Oxygen-stabilized glass formation in Zr80Pt20 melt-spun ribbons"

Authors: D.J. Sordelet, X.Y. Yang, E.A. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: Appl. Phys. Lett. (2003) 83, 69-71.

Abstract:
The as-quenched structure of Zr80Pt20 melt-spun ribbons containing measured oxygen contents ranging from 184 to 4737 ppm mass was studied. Ribbons containing less than 500 ppm mass oxygen are fully crystallized and consist predominantly of a metastable ordered Β-Zr phase with significant solution of Pt. Increasing oxygen content to 1053 and 1547 ppm mass produces a transition to fully amorphous and to mixed amorphous and quasicrystalline structures, respectively. Samples containing 4737 ppm mass consist of quasicrystalline and crystalline phases in an amorphous matrix. The results from this study suggest a critical level of oxygen is required to promote glass formation in Zr80Pt20 melt-spun ribbons produced at a specific quench rate.

Title: "Devitrification studies of Zr-Pd and Zr-Pd-Cu metallic glasses"

Authors: M.J. Kramer, M.F. Besser, N. Yang, E. Rozhkova, D.J. Sordelet, Y. Zhang, and P.L. Lee

Contact: D.J. Sordelet

Journal: J. Non-Cryst. Solids (2003) 317(1-2), 62-70.

Abstract:

High temperature X-ray diffraction (HTXRD) is used to investigate the devitrification pathway for two related Zr-based metallic glasses, Zr70Pd30 and Zr70Pd20Cu10. Both alloys have similar as-quenched structures and initially devitrify to form a meta-stable quasicrystalline phase. The HTXRD data for the Zr70Pd30 alloy shows the coexistence of the quasicrystalline and the Zr2Pd (I4/mmm) crystalline phases over a range of 25 K. Conversely, the Zr70Pd20Cu10 alloy shows an additional transformation of the quasicrystalline phase to a meta-stable Zr2(PdCu) intermetallic (Zr2Si type structure, I4/mcm) that polymorphically transforms to the Zr2Ni type structure (I4/mmm) over a very narrow temperature range.

Title: "Consolidation of gas atomized Cu47Ti34Zr11Ni8 amorphous powders"

Authors: D.J. Sordelet, E. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: J. Non-Cryst. Solids (2003) 317, 137-143.

Abstract:

The dense, random atomic configuration of bulk metallic glasses enhances their stability against crystallization in the supercooled liquid state. This stability provides the opportunity to deform the material by plastic processing methods such as warm extrusion. Gas atomized Cu47Ti34Zr11Ni8 powders were consolidated at various temperatures above their glass transition temperature (688 K) at extrusion ratios of 5, 9 and 13. At extrusion temperatures approaching Tx (743 K), powders consolidated at an extrusion ratio of 5 were predominantly amorphous while at higher ratios the powders were completely devitrified, yet fully consolidated. Gradients in the degree of devitrification were observed along the length (i.e., top to bottom) of all extruded materials.

Title: "Oxygen effects on glass formation of plasma arc sprayed Cu47Ti33Zr11Ni8Si1 surface coatings"

Authors: D.J. Sordelet and M.F. Besser

Contact: D.J. Sordelet

Journal: Mater. Sci. Eng., A (2004) 375-377, 625-629.

Abstract:

A series of thermal spray experiments were performed to produce Cu47Ti33Zr11Ni8Si1 coatings from gas atomized powders synthesized with oxygen contents ranging from 0.125 to 0.79 wt.%. The amount of oxygen increased with decreasing particle size, which suggests the oxide is present as a surface film. Surface coatings were deposited using plasma arc spraying (PAS) in air and in an argon environment within an environmental chamber. The amount of amorphous phase was estimated for the gas atomized powders and plasma arc sprayed coatings. Despite the rapid solidification occurring during these two processing methods, substantial devitrification occurs in the high oxygen content powders and their associated coatings. Coatings deposited in air exhibit significantly more devitrification than their counterparts produced in the controlled environment chamber.

Title: "Formation of quasicrystals in Zr-Pd-(Cu) melt spun ribbons and mechanically milled powders"

Authors: D.J. Sordelet, E. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: Intermetallics (2002) 10(11-12), 1233-1240.

Abstract:

Amorphous Zr70Pd30 and Zr70Pd20Cu10 alloys were prepared by mechanical milling and melt spinnng to compare their devitrification behaviors. The devitrification of mechanical milled Zr70Pd30 and Zr70Pd20Cu10 powders occurs via a single-step, first-order transformation to a stable Zr2Pd tetragonal structure. This is in sharp contrast to the devitrification of the same amorphous alloys prepared by melt spinning, in which a primary meta-stable quasicrystalline phase forms. Since the mechanical milling process does not involve direct liquid phase formation of an amorphous structure, it is inferred that the short-range order in the solid state derived amorphous powder is different from that in the melt spun ribbon. During mechanical milling of an amorphous melt spun ribbon, crystalization of the quasicrystalline phase appears to precede disordering into an amorphous structure having an different short range order. Deformation of an amorphous melt spun ribbon by repetitive rolling at ambient temperature crystallizes the meta-stable quasicrystalline phase.

Title: "Synthesis route-dependent formation of quasicrystals in Zr70Pd30 and Zr70Pd20Cu10 amorphous alloys"

Authors: D.J. Sordelet, E. Rozhkova, M.F. Besser, and M.J. Kramer

Contact: D.J. Sordelet

Journal: Appl. Phys. Lett. (2002) 80(25), 4735-4737.

Abstract:

The devitrification of mech. milled amorphous Zr70Pd30 and Zr70Pd20Cu10 powders occurs via a single-step, first-order transformation to a stable Zr2Pd tetragonal structure. This is in sharp contrast to the devitrification of the same amorphous alloys prepared by melt spinning, in which a primary metastable quasicrystalline phase forms. Since the mechanical milling process does not involve direct liquid phase formation of an amorphous structure, it is inferred that the short-range order in the solid state derived amorphous powder is different from that in the melt spun ribbon.

Title: "Synthesis of Cu47Ti34Zr11Ni8 bulk metallic glass by warm extrusion of gas atomized powders"

Authors: D.J. Sordelet, E. Rozhkova, P. Huang, P.B. Wheelock, M.F. Besser, M.J. Kramer, M. Calvo-Dahlborg, and U. Dahlborg

Contact: D.J. Sordelet

Journal: J. Mater. Res. (2002) 17, 186-198.

Abstract:

Cu47Ti34Zr11Ni8 amorphous gas atomized powders were consolidated by warm extrusion. After consolidation near 723 K using an extrusion ratio of 5, the material retains between 88% and 98% of the amorphous structure found in the gas atomized powder. The onsets of the glass transition and crystallization temperatures of this extruded material are observed respectively at slightly higher and lower temperatures than those of the starting powders. These temperature shifts are attributed to a composition change in the remaining amorphous phase during partial devitrification throughout the extrusion process. Powders extruded at the same temperature, but using higher extrusion ratios of 9 and 13, exhibit substantial devitrification during the consolidation process yet still deform homogeneously.

Title: "Time-resolved studies of Ti34-xCu47Zr11Ni8Six metallic glass devitrification using high temperature x-ray powder diffraction"

Authors: D.J. Sordelet, M.J. Kramer, M.F. Besser, and E. Rozhkova

Contact: D.J. Sordelet

Journal: J. Non-Cryst. Solids (2001) 290, 163-172.

Abstract:

Time-resolved devitrification studies of Ti34-xCu47Zr11Ni8Six metallic glasses were performed using a recently developed high temperature furnace in a Debye–Scherrer geometry. Samples included powders produced by high pressure gas atomization and surface coatings deposited by air plasma spraying. Synchrotron radiation at the Advanced Photon Source at Argonne National Laboratory was used to follow the devitrification of samples during heating at 40 K min-1 between 623 and 1073 K. The crystallization behavior observed with structural diffraction data compare well with results from thermal analysis using differential scanning calorimetery. At 1073 K, these amorphous alloys evolve to a four phase microstructure which includes phases that appear to be closely related to Cu51Zr14, CuTi and Cu2TiZr.


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